- 21 Jan, 2022 6 commits
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Andrii Nakryiko authored
Introduce 4 new netlink-based XDP APIs for attaching, detaching, and querying XDP programs: - bpf_xdp_attach; - bpf_xdp_detach; - bpf_xdp_query; - bpf_xdp_query_id. These APIs replace bpf_set_link_xdp_fd, bpf_set_link_xdp_fd_opts, bpf_get_link_xdp_id, and bpf_get_link_xdp_info APIs ([0]). The latter don't follow a consistent naming pattern and some of them use non-extensible approaches (e.g., struct xdp_link_info which can't be modified without breaking libbpf ABI). The approach I took with these low-level XDP APIs is similar to what we did with low-level TC APIs. There is a nice duality of bpf_tc_attach vs bpf_xdp_attach, and so on. I left bpf_xdp_attach() to support detaching when -1 is specified for prog_fd for generality and convenience, but bpf_xdp_detach() is preferred due to clearer naming and associated semantics. Both bpf_xdp_attach() and bpf_xdp_detach() accept the same opts struct allowing to specify expected old_prog_fd. While doing the refactoring, I noticed that old APIs require users to specify opts with old_fd == -1 to declare "don't care about already attached XDP prog fd" condition. Otherwise, FD 0 is assumed, which is essentially never an intended behavior. So I made this behavior consistent with other kernel and libbpf APIs, in which zero FD means "no FD". This seems to be more in line with the latest thinking in BPF land and should cause less user confusion, hopefully. For querying, I left two APIs, both more generic bpf_xdp_query() allowing to query multiple IDs and attach mode, but also a specialization of it, bpf_xdp_query_id(), which returns only requested prog_id. Uses of prog_id returning bpf_get_link_xdp_id() were so prevalent across selftests and samples, that it seemed a very common use case and using bpf_xdp_query() for doing it felt very cumbersome with a highly branches if/else chain based on flags and attach mode. Old APIs are scheduled for deprecation in libbpf 0.8 release. [0] Closes: https://github.com/libbpf/libbpf/issues/309Signed-off-by:
Andrii Nakryiko <andrii@kernel.org> Acked-by:
Toke Høiland-Jørgensen <toke@redhat.com> Link: https://lore.kernel.org/r/20220120061422.2710637-2-andrii@kernel.orgSigned-off-by:
Alexei Starovoitov <ast@kernel.org>
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Alexei Starovoitov authored
Andrii Nakryiko says: ==================== Officially deprecate legacy BPF map definitions in libbpf. They've been slated for deprecation for a while in favor of more powerful BTF-defined map definitions and this patch set adds warnings and a way to enforce this in libbpf through LIBBPF_STRICT_MAP_DEFINITIONS strict mode flag. Selftests are fixed up and updated, BPF documentation is updated, bpftool's strict mode usage is adjusted to avoid breaking users unnecessarily. v1->v2: - replace missed bpf_map_def case in Documentation/bpf/btf.rst (Alexei). ==================== Signed-off-by: -
Andrii Nakryiko authored
Use BTF-defined map definition in the documentation example. Signed-off-by:
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Andrii Nakryiko authored
Enact deprecation of legacy BPF map definition in SEC("maps") ([0]). For the definitions themselves introduce LIBBPF_STRICT_MAP_DEFINITIONS flag for libbpf strict mode. If it is set, error out on any struct bpf_map_def-based map definition. If not set, libbpf will print out a warning for each legacy BPF map to raise awareness that it goes away. For any use of BPF_ANNOTATE_KV_PAIR() macro providing a legacy way to associate BTF key/value type information with legacy BPF map definition, warn through libbpf's pr_warn() error message (but don't fail BPF object open). BPF-side struct bpf_map_def is marked as deprecated. User-space struct bpf_map_def has to be used internally in libbpf, so it is left untouched. It should be enough for bpf_map__def() to be marked deprecated to raise awareness that it goes away. bpftool is an interesting case that utilizes libbpf to open BPF ELF object to generate skeleton. As such, even though bpftool itself uses full on strict libbpf mode (LIBBPF_STRICT_ALL), it has to relax it a bit for BPF map definition handling to minimize unnecessary disruptions. So opt-out of LIBBPF_STRICT_MAP_DEFINITIONS for bpftool. User's code that will later use generated skeleton will make its own decision whether to enforce LIBBPF_STRICT_MAP_DEFINITIONS or not. There are few tests in selftests/bpf that are consciously using legacy BPF map definitions to test libbpf functionality. For those, temporary opt out of LIBBPF_STRICT_MAP_DEFINITIONS mode for the duration of those tests. [0] Closes: https://github.com/libbpf/libbpf/issues/272Signed-off-by: -
Andrii Nakryiko authored
Converted few remaining legacy BPF map definition to BTF-defined ones. For the remaining two bpf_map_def-based legacy definitions that we want to keep for testing purposes until libbpf 1.0 release, guard them in pragma to suppres deprecation warnings which will be added in libbpf in the next commit. Signed-off-by:
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Andrii Nakryiko authored
It's very easy to miss compilation warnings without -Werror, which is not set for selftests. libbpf and bpftool are already strict about this, so make selftests/bpf also treat compilation warnings as errors to catch such regressions early. Signed-off-by:
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- 20 Jan, 2022 5 commits
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Kumar Kartikeya Dwivedi authored
Some users have complained that selftests fail to build when CONFIG_NF_CONNTRACK=m. It would be useful to allow building as long as it is set to module or built-in, even though in case of building as module, user would need to load it before running the selftest. Note that this also allows building selftest when CONFIG_NF_CONNTRACK is disabled. Signed-off-by:
Kumar Kartikeya Dwivedi <memxor@gmail.com> Signed-off-by:
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Felix Maurer authored
The bind_perm BPF selftest failed when port 111/tcp was already in use during the test. To fix this, the test now runs in its own network name space. To use unshare, it is necessary to reorder the includes. The style of the includes is adapted to be consistent with the other prog_tests. v2: Replace deprecated CHECK macro with ASSERT_OK Fixes: 8259fdeb ("selftests/bpf: Verify that rebinding to port < 1024 from BPF works") Signed-off-by:
Felix Maurer <fmaurer@redhat.com> Signed-off-by:
Jakub Sitnicki <jakub@cloudflare.com> Link: https://lore.kernel.org/bpf/551ee65533bb987a43f93d88eaf2368b416ccd32.1642518457.git.fmaurer@redhat.com
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Andrii Nakryiko authored
Lorenzo Bianconi says: ==================== Rely on ASSERT* macros and get rid of deprecated CHECK ones in xdp_bpf2bpf and xdp_adjust_tail bpf selftests. This is a preliminary series for XDP multi-frags support. Changes since v1: - run each ASSERT test separately - drop unnecessary return statements - drop unnecessary if condition in test_xdp_bpf2bpf() ==================== Signed-off-by: -
Lorenzo Bianconi authored
Rely on ASSERT* macros and get rid of deprecated CHECK ones in xdp_bpf2bpf bpf selftest. Signed-off-by:
Lorenzo Bianconi <lorenzo@kernel.org> Signed-off-by:
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Lorenzo Bianconi authored
Rely on ASSERT* macros and get rid of deprecated CHECK ones in xdp_adjust_tail bpf selftest. Signed-off-by:
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- 19 Jan, 2022 12 commits
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Alexei Starovoitov authored
YiFei Zhu says: ==================== Right now, most cgroup hooks are best used for permission checks. They can only reject a syscall with -EPERM, so a cause of a rejection, if the rejected by eBPF cgroup hooks, is ambiguous to userspace. Additionally, if the syscalls are implemented in eBPF, all permission checks and the implementation has to happen within the same filter, as programs executed later in the series of progs are unaware of the return values return by the previous progs. This patch series adds two helpers, bpf_get_retval and bpf_set_retval, that allows hooks to get/set the return value of syscall to userspace. This also allows later progs to retrieve retval set by previous progs. For legacy programs that rejects a syscall without setting the retval, for backwards compatibility, if a prog rejects without itself or a prior prog setting retval to an -err, the retval is set by the kernel to -EPERM. For getsockopt hooks that has ctx->retval, this variable mirrors that that accessed by the helpers. Additionally, the following user-visible behavior for getsockopt hooks has changed: - If a prior filter rejected the syscall, it will be visible in ctx->retval. - Attempting to change the retval arbitrarily is now allowed and will not cause an -EFAULT. - If kernel rejects a getsockopt syscall before running the hooks, the error will be visible in ctx->retval. Returning 0 from the prog will not overwrite the error to -EPERM unless there is an explicit call of bpf_set_retval(-EPERM) Tests have been added in this series to test the behavior of the helper with cgroup setsockopt getsockopt hooks. Patch 1 changes the API of macros to prepare for the next patch and should be a no-op. Patch 2 moves ctx->retval to a struct pointed to by current task_struct. Patch 3 implements the helpers. Patch 4 tests the behaviors of the helpers. Patch 5 updates a test after the test broke due to the visible changes. v1 -> v2: - errno -> retval - split one helper to get & set helpers - allow retval to be set arbitrarily in the general case - made the helper retval and context retval mirror each other ==================== Signed-off-by: -
YiFei Zhu authored
The tests would break without this patch, because at one point it calls getsockopt(fd, SOL_TCP, TCP_ZEROCOPY_RECEIVE, &buf, &optlen) This getsockopt receives the kernel-set -EINVAL. Prior to this patch series, the eBPF getsockopt hook's -EPERM would override kernel's -EINVAL, however, after this patch series, return 0's automatic -EPERM will not; the eBPF prog has to explicitly bpf_set_retval(-EPERM) if that is wanted. I also removed the explicit mentions of EPERM in the comments in the prog. Signed-off-by:
YiFei Zhu <zhuyifei@google.com> Reviewed-by:
Stanislav Fomichev <sdf@google.com> Link: https://lore.kernel.org/r/4f20b77cb46812dbc2bdcd7e3fa87c7573bde55e.1639619851.git.zhuyifei@google.comSigned-off-by:
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YiFei Zhu authored
The tests checks how different ways of interacting with the helpers (getting retval, setting EUNATCH, EISCONN, and legacy reject returning 0 without setting retval), produce different results in both the setsockopt syscall and the retval returned by the helper. A few more tests verify the interaction between the retval of the helper and the retval in getsockopt context. Signed-off-by:
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YiFei Zhu authored
The helpers continue to use int for retval because all the hooks are int-returning rather than long-returning. The return value of bpf_set_retval is int for future-proofing, in case in the future there may be errors trying to set the retval. After the previous patch, if a program rejects a syscall by returning 0, an -EPERM will be generated no matter if the retval is already set to -err. This patch change it being forced only if retval is not -err. This is because we want to support, for example, invoking bpf_set_retval(-EINVAL) and return 0, and have the syscall return value be -EINVAL not -EPERM. For BPF_PROG_CGROUP_INET_EGRESS_RUN_ARRAY, the prior behavior is that, if the return value is NET_XMIT_DROP, the packet is silently dropped. We preserve this behavior for backward compatibility reasons, so even if an errno is set, the errno does not return to caller. However, setting a non-err to retval cannot propagate so this is not allowed and we return a -EFAULT in that case. Signed-off-by:
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YiFei Zhu authored
The retval value is moved to struct bpf_cg_run_ctx for ease of access in different prog types with different context structs layouts. The helper implementation (to be added in a later patch in the series) can simply perform a container_of from current->bpf_ctx to retrieve bpf_cg_run_ctx. Unfortunately, there is no easy way to access the current task_struct via the verifier BPF bytecode rewrite, aside from possibly calling a helper, so a pointer to current task is added to struct bpf_sockopt_kern so that the rewritten BPF bytecode can access struct bpf_cg_run_ctx with an indirection. For backward compatibility, if a getsockopt program rejects a syscall by returning 0, an -EPERM will be generated, by having the BPF_PROG_RUN_ARRAY_CG family macros automatically set the retval to -EPERM. Unlike prior to this patch, this -EPERM will be visible to ctx->retval for any other hooks down the line in the prog array. Additionally, the restriction that getsockopt filters can only set the retval to 0 is removed, considering that certain getsockopt implementations may return optlen. Filters are now able to set the value arbitrarily. Signed-off-by:
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YiFei Zhu authored
Right now BPF_PROG_RUN_ARRAY and related macros return 1 or 0 for whether the prog array allows or rejects whatever is being hooked. The caller of these macros then return -EPERM or continue processing based on thw macro's return value. Unforunately this is inflexible, since -EPERM is the only err that can be returned. This patch should be a no-op; it prepares for the next patch. The returning of the -EPERM is moved to inside the macros, so the outer functions are directly returning what the macros returned if they are non-zero. Signed-off-by:
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Kui-Feng Lee authored
Add a hashmap to map the string offsets from a source btf to the string offsets from a target btf to reduce overheads. btf__add_btf() calls btf__add_str() to add strings from a source to a target btf. It causes many string comparisons, and it is a major hotspot when adding a big btf. btf__add_str() uses strcmp() to check if a hash entry is the right one. The extra hashmap here compares offsets of strings, that are much cheaper. It remembers the results of btf__add_str() for later uses to reduce the cost. We are parallelizing BTF encoding for pahole by creating separated btf instances for worker threads. These per-thread btf instances will be added to the btf instance of the main thread by calling btf__add_str() to deduplicate and write out. With this patch and -j4, the running time of pahole drops to about 6.0s from 6.6s. The following lines are the summary of 'perf stat' w/o the change. 6.668126396 seconds time elapsed 13.451054000 seconds user 0.715520000 seconds sys The following lines are the summary w/ the change. 5.986973919 seconds time elapsed 12.939903000 seconds user 0.724152000 seconds sys V4 fixes a bug of error checking against the pointer returned by hashmap__new(). [v3] https://lore.kernel.org/bpf/20220118232053.2113139-1-kuifeng@fb.com/ [v2] https://lore.kernel.org/bpf/20220114193713.461349-1-kuifeng@fb.com/Signed-off-by:Kui-Feng Lee <kuifeng@fb.com> Signed-off-by:
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Usama Arif authored
Currently the syscalls rst and subsequently man page are auto-generated using function documentation present in bpf.h. If the documentation for the syscall is missing or doesn't follow a specific format, then that syscall is not dumped in the auto-generated rst. This patch checks the number of syscalls documented within the header file with those present as part of the enum bpf_cmd and raises an Exception if they don't match. It is not needed with the currently documented upstream syscalls, but can help in debugging when developing new syscalls when there might be missing or misformatted documentation. The function helper_number_check is moved to the Printer parent class and renamed to elem_number_check as all the most derived children classes are using this function now. Signed-off-by:
Usama Arif <usama.arif@bytedance.com> Signed-off-by:
Quentin Monnet <quentin@isovalent.com> Link: https://lore.kernel.org/bpf/20220119114442.1452088-3-usama.arif@bytedance.com
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Usama Arif authored
This enforce a minimal formatting consistency for the documentation. The description and returns missing for a few helpers have also been added. Signed-off-by:
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Usama Arif authored
Both description and returns section will become mandatory for helpers and syscalls in a later commit to generate man pages. This commit also adds in the documentation that BPF_PROG_RUN is an alias for BPF_PROG_TEST_RUN for anyone searching for the syscall in the generated man pages. Signed-off-by:
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Raman Shukhau authored
`bpftool prog list` and other bpftool subcommands that show BPF program names currently get them from bpf_prog_info.name. That field is limited to 16 (BPF_OBJ_NAME_LEN) chars which leads to truncated names since many progs have much longer names. The idea of this change is to improve all bpftool commands that output prog name so that bpftool uses info from BTF to print program names if available. It tries bpf_prog_info.name first and fall back to btf only if the name is suspected to be truncated (has 15 chars length). Right now `bpftool p show id <id>` returns capped prog name <id>: kprobe name example_cap_cap tag 712e... ... With this change it would return <id>: kprobe name example_cap_capable tag 712e... ... Note, other commands that print prog names (e.g. "bpftool cgroup tree") are also addressed in this change. Signed-off-by:
Raman Shukhau <ramasha@fb.com> Signed-off-by:
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Toke Høiland-Jørgensen authored
The btf.h header included with libbpf contains inline helper functions to check for various BTF kinds. These helpers directly reference the BTF_KIND_* constants defined in the kernel header, and because the header file is included in user applications, this happens in the user application compile units. This presents a problem if a user application is compiled on a system with older kernel headers because the constants are not available. To avoid this, add #defines of the constants directly in btf.h before using them. Since the kernel header moved to an enum for BTF_KIND_*, the #defines can shadow the enum values without any errors, so we only need #ifndef guards for the constants that predates the conversion to enum. We group these so there's only one guard for groups of values that were added together. [0] Closes: https://github.com/libbpf/libbpf/issues/436 Fixes: 223f903e ("bpf: Rename BTF_KIND_TAG to BTF_KIND_DECL_TAG") Fixes: 5b84bd10 ("libbpf: Add support for BTF_KIND_TAG") Signed-off-by:
Arnaldo Carvalho de Melo <acme@redhat.com> Link: https://lore.kernel.org/bpf/20220118141327.34231-1-toke@redhat.com
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- 18 Jan, 2022 17 commits
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Alexei Starovoitov authored
Kuniyuki Iwashima says: ==================== Last year the commit afd20b92 ("af_unix: Replace the big lock with small locks.") landed on bpf-next. Now we can use a batching algorithm for AF_UNIX bpf iter as TCP bpf iter. Changelog: - Add the 1st patch. - Call unix_get_first() in .start()/.next() to always acquire a lock in each iteration in the 2nd patch. ==================== Signed-off-by:
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Kuniyuki Iwashima authored
The commit b8a58aa6 ("af_unix: Cut unix_validate_addr() out of unix_mkname().") moved the bound test part into unix_validate_addr(). Signed-off-by:
Kuniyuki Iwashima <kuniyu@amazon.co.jp> Link: https://lore.kernel.org/r/20220113002849.4384-6-kuniyu@amazon.co.jpSigned-off-by:
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Kuniyuki Iwashima authored
This patch adds a test for the batching and bpf_(get|set)sockopt in bpf unix iter. It does the following. 1. Creates an abstract UNIX domain socket 2. Call bpf_setsockopt() 3. Call bpf_getsockopt() and save the value 4. Call setsockopt() 5. Call getsockopt() and save the value 6. Compare the saved values Signed-off-by:
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Kuniyuki Iwashima authored
This patch makes bpf_(get|set)sockopt() available when iterating AF_UNIX sockets. Signed-off-by:
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Kuniyuki Iwashima authored
The commit 04c7820b ("bpf: tcp: Bpf iter batching and lock_sock") introduces the batching algorithm to iterate TCP sockets with more consistency. This patch uses the same algorithm to iterate AF_UNIX sockets. Signed-off-by:
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Kuniyuki Iwashima authored
Currently, unix_next_socket() is overloaded depending on the 2nd argument. If it is NULL, unix_next_socket() returns the first socket in the hash. If not NULL, it returns the next socket in the same hash list or the first socket in the next non-empty hash list. This patch refactors unix_next_socket() into two functions unix_get_first() and unix_get_next(). unix_get_first() newly acquires a lock and returns the first socket in the list. unix_get_next() returns the next socket in a list or releases a lock and falls back to unix_get_first(). In the following patch, bpf iter holds entire sockets in a list and always releases the lock before .show(). It always calls unix_get_first() to acquire a lock in each iteration. So, this patch makes the change easier to follow. Signed-off-by:
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Alexei Starovoitov authored
Kumar Kartikeya says: ==================== This series adds unstable conntrack lookup helpers using BPF kfunc support. The patch adding the lookup helper is based off of Maxim's recent patch to aid in rebasing their series on top of this, all adjusted to work with module kfuncs [0]. [0]: https://lore.kernel.org/bpf/20211019144655.3483197-8-maximmi@nvidia.com To enable returning a reference to struct nf_conn, the verifier is extended to support reference tracking for PTR_TO_BTF_ID, and kfunc is extended with support for working as acquire/release functions, similar to existing BPF helpers. kfunc returning pointer (limited to PTR_TO_BTF_ID in the kernel) can also return a PTR_TO_BTF_ID_OR_NULL now, typically needed when acquiring a resource can fail. kfunc can also receive PTR_TO_CTX and PTR_TO_MEM (with some limitations) as arguments now. There is also support for passing a mem, len pair as argument to kfunc now. In such cases, passing pointer to unsized type (void) is also permitted. Please see individual commits for details. Changelog: ---------- v7 -> v8: v7: https://lore.kernel.org/bpf/20220111180428.931466-1-memxor@gmail.com * Move enum btf_kfunc_hook to btf.c (Alexei) * Drop verbose log for unlikely failure case in __find_kfunc_desc_btf (Alexei) * Remove unnecessary barrier in register_btf_kfunc_id_set (Alexei) * Switch macro in bpf_nf test to __always_inline function (Alexei) v6 -> v7: v6: https://lore.kernel.org/bpf/20220102162115.1506833-1-memxor@gmail.com * Drop try_module_get_live patch, use flag in btf_module struct (Alexei) * Add comments and expand commit message detailing why we have to concatenate and sort vmlinux kfunc BTF ID sets (Alexei) * Use bpf_testmod for testing btf_try_get_module race (Alexei) * Use bpf_prog_type for both btf_kfunc_id_set_contains and register_btf_kfunc_id_set calls (Alexei) * In case of module set registration, directly assign set (Alexei) * Add CONFIG_USERFAULTFD=y to selftest config * Fix other nits v5 -> v6: v5: https://lore.kernel.org/bpf/20211230023705.3860970-1-memxor@gmail.com * Fix for a bug in btf_try_get_module leading to use-after-free * Drop *kallsyms_on_each_symbol loop, reinstate register_btf_kfunc_id_set (Alexei) * btf_free_kfunc_set_tab now takes struct btf, and handles resetting tab to NULL * Check return value btf_name_by_offset for param_name * Instead of using tmp_set, use btf->kfunc_set_tab directly, and simplify cleanup v4 -> v5: v4: https://lore.kernel.org/bpf/20211217015031.1278167-1-memxor@gmail.com * Move nf_conntrack helpers code to its own separate file (Toke, Pablo) * Remove verifier callbacks, put btf_id_sets in struct btf (Alexei) * Convert the in-kernel users away from the old API * Change len__ prefix convention to __sz suffix (Alexei) * Drop parent_ref_obj_id patch (Alexei) v3 -> v4: v3: https://lore.kernel.org/bpf/20211210130230.4128676-1-memxor@gmail.com * Guard unstable CT helpers with CONFIG_DEBUG_INFO_BTF_MODULES * Move addition of prog_test test kfuncs to selftest commit * Move negative kfunc tests to test_verifier suite * Limit struct nesting depth to 4, which should be enough for now v2 -> v3: v2: https://lore.kernel.org/bpf/20211209170929.3485242-1-memxor@gmail.com * Fix build error for !CONFIG_BPF_SYSCALL (Patchwork) RFC v1 -> v2: v1: https://lore.kernel.org/bpf/20211030144609.263572-1-memxor@gmail.com * Limit PTR_TO_MEM support to pointer to scalar, or struct with scalars (Alexei) * Use btf_id_set for checking acquire, release, ret type null (Alexei) * Introduce opts struct for CT helpers, move int err parameter to it * Add l4proto as parameter to CT helper's opts, remove separate tcp/udp helpers * Add support for mem, len argument pair to kfunc * Allow void * as pointer type for mem, len argument pair * Extend selftests to cover new additions to kfuncs * Copy ref_obj_id to PTR_TO_BTF_ID dst_reg on btf_struct_access, test it * Fix other misc nits, bugs, and expand commit messages ==================== Signed-off-by:
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Kumar Kartikeya Dwivedi authored
This adds a complete test case to ensure we never take references to modules not in MODULE_STATE_LIVE, which can lead to UAF, and it also ensures we never access btf->kfunc_set_tab in an inconsistent state. The test uses userfaultfd to artificially widen the race. When run on an unpatched kernel, it leads to the following splat: [root@(none) bpf]# ./test_progs -t bpf_mod_race/ksym [ 55.498171] BUG: unable to handle page fault for address: fffffbfff802548b [ 55.499206] #PF: supervisor read access in kernel mode [ 55.499855] #PF: error_code(0x0000) - not-present page [ 55.500555] PGD a4fa9067 P4D a4fa9067 PUD a4fa5067 PMD 1b44067 PTE 0 [ 55.501499] Oops: 0000 [#1] PREEMPT SMP KASAN NOPTI [ 55.502195] CPU: 0 PID: 83 Comm: kworker/0:2 Tainted: G OE 5.16.0-rc4+ #151 [ 55.503388] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ArchLinux 1.15.0-1 04/01/2014 [ 55.504777] Workqueue: events bpf_prog_free_deferred [ 55.505563] RIP: 0010:kasan_check_range+0x184/0x1d0 [ 55.509140] RSP: 0018:ffff88800560fcf0 EFLAGS: 00010282 [ 55.509977] RAX: fffffbfff802548b RBX: fffffbfff802548c RCX: ffffffff9337b6ba [ 55.511096] RDX: fffffbfff802548c RSI: 0000000000000004 RDI: ffffffffc012a458 [ 55.512143] RBP: fffffbfff802548b R08: 0000000000000001 R09: ffffffffc012a45b [ 55.513228] R10: fffffbfff802548b R11: 0000000000000001 R12: ffff888001b5f598 [ 55.514332] R13: ffff888004f49ac8 R14: 0000000000000000 R15: ffff888092449400 [ 55.515418] FS: 0000000000000000(0000) GS:ffff888092400000(0000) knlGS:0000000000000000 [ 55.516705] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 55.517560] CR2: fffffbfff802548b CR3: 0000000007c10006 CR4: 0000000000770ef0 [ 55.518672] PKRU: 55555554 [ 55.519022] Call Trace: [ 55.519483] <TASK> [ 55.519884] module_put.part.0+0x2a/0x180 [ 55.520642] bpf_prog_free_deferred+0x129/0x2e0 [ 55.521478] process_one_work+0x4fa/0x9e0 [ 55.522122] ? pwq_dec_nr_in_flight+0x100/0x100 [ 55.522878] ? rwlock_bug.part.0+0x60/0x60 [ 55.523551] worker_thread+0x2eb/0x700 [ 55.524176] ? __kthread_parkme+0xd8/0xf0 [ 55.524853] ? process_one_work+0x9e0/0x9e0 [ 55.525544] kthread+0x23a/0x270 [ 55.526088] ? set_kthread_struct+0x80/0x80 [ 55.526798] ret_from_fork+0x1f/0x30 [ 55.527413] </TASK> [ 55.527813] Modules linked in: bpf_testmod(OE) [last unloaded: bpf_testmod] [ 55.530846] CR2: fffffbfff802548b [ 55.531341] ---[ end trace 1af41803c054ad6d ]--- [ 55.532136] RIP: 0010:kasan_check_range+0x184/0x1d0 [ 55.535887] RSP: 0018:ffff88800560fcf0 EFLAGS: 00010282 [ 55.536711] RAX: fffffbfff802548b RBX: fffffbfff802548c RCX: ffffffff9337b6ba [ 55.537821] RDX: fffffbfff802548c RSI: 0000000000000004 RDI: ffffffffc012a458 [ 55.538899] RBP: fffffbfff802548b R08: 0000000000000001 R09: ffffffffc012a45b [ 55.539928] R10: fffffbfff802548b R11: 0000000000000001 R12: ffff888001b5f598 [ 55.541021] R13: ffff888004f49ac8 R14: 0000000000000000 R15: ffff888092449400 [ 55.542108] FS: 0000000000000000(0000) GS:ffff888092400000(0000) knlGS:0000000000000000 [ 55.543260]CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 55.544136] CR2: fffffbfff802548b CR3: 0000000007c10006 CR4: 0000000000770ef0 [ 55.545317] PKRU: 55555554 [ 55.545671] note: kworker/0:2[83] exited with preempt_count 1 Signed-off-by:
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Kumar Kartikeya Dwivedi authored
Use the prog_test kfuncs to test the referenced PTR_TO_BTF_ID kfunc support, and PTR_TO_CTX, PTR_TO_MEM argument passing support. Also testing the various failure cases for invalid kfunc prototypes. Signed-off-by:
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Kumar Kartikeya Dwivedi authored
This allows us to add tests (esp. negative tests) where we only want to ensure the program doesn't pass through the verifier, and also verify the error. The next commit will add the tests making use of this. Signed-off-by:
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Kumar Kartikeya Dwivedi authored
This tests that we return errors as documented, and also that the kfunc calls work from both XDP and TC hooks. Signed-off-by:
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Kumar Kartikeya Dwivedi authored
This change adds conntrack lookup helpers using the unstable kfunc call interface for the XDP and TC-BPF hooks. The primary usecase is implementing a synproxy in XDP, see Maxim's patchset [0]. Export get_net_ns_by_id as nf_conntrack_bpf.c needs to call it. This object is only built when CONFIG_DEBUG_INFO_BTF_MODULES is enabled. [0]: https://lore.kernel.org/bpf/20211019144655.3483197-1-maximmi@nvidia.comSigned-off-by:
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Kumar Kartikeya Dwivedi authored
This patch adds verifier support for PTR_TO_BTF_ID return type of kfunc to be a reference, by reusing acquire_reference_state/release_reference support for existing in-kernel bpf helpers. We make use of the three kfunc types: - BTF_KFUNC_TYPE_ACQUIRE Return true if kfunc_btf_id is an acquire kfunc. This will acquire_reference_state for the returned PTR_TO_BTF_ID (this is the only allow return value). Note that acquire kfunc must always return a PTR_TO_BTF_ID{_OR_NULL}, otherwise the program is rejected. - BTF_KFUNC_TYPE_RELEASE Return true if kfunc_btf_id is a release kfunc. This will release the reference to the passed in PTR_TO_BTF_ID which has a reference state (from earlier acquire kfunc). The btf_check_func_arg_match returns the regno (of argument register, hence > 0) if the kfunc is a release kfunc, and a proper referenced PTR_TO_BTF_ID is being passed to it. This is similar to how helper call check uses bpf_call_arg_meta to store the ref_obj_id that is later used to release the reference. Similar to in-kernel helper, we only allow passing one referenced PTR_TO_BTF_ID as an argument. It can also be passed in to normal kfunc, but in case of release kfunc there must always be one PTR_TO_BTF_ID argument that is referenced. - BTF_KFUNC_TYPE_RET_NULL For kfunc returning PTR_TO_BTF_ID, tells if it can be NULL, hence force caller to mark the pointer not null (using check) before accessing it. Note that taking into account the case fixed by commit 93c230e3 ("bpf: Enforce id generation for all may-be-null register type") we assign a non-zero id for mark_ptr_or_null_reg logic. Later, if more return types are supported by kfunc, which have a _OR_NULL variant, it might be better to move this id generation under a common reg_type_may_be_null check, similar to the case in the commit. Referenced PTR_TO_BTF_ID is currently only limited to kfunc, but can be extended in the future to other BPF helpers as well. For now, we can rely on the btf_struct_ids_match check to ensure we get the pointer to the expected struct type. In the future, care needs to be taken to avoid ambiguity for reference PTR_TO_BTF_ID passed to release function, in case multiple candidates can release same BTF ID. e.g. there might be two release kfuncs (or kfunc and helper): foo(struct abc *p); bar(struct abc *p); ... such that both release a PTR_TO_BTF_ID with btf_id of struct abc. In this case we would need to track the acquire function corresponding to the release function to avoid type confusion, and store this information in the register state so that an incorrect program can be rejected. This is not a problem right now, hence it is left as an exercise for the future patch introducing such a case in the kernel. Signed-off-by: -
Kumar Kartikeya Dwivedi authored
BPF helpers can associate two adjacent arguments together to pass memory of certain size, using ARG_PTR_TO_MEM and ARG_CONST_SIZE arguments. Since we don't use bpf_func_proto for kfunc, we need to leverage BTF to implement similar support. The ARG_CONST_SIZE processing for helpers is refactored into a common check_mem_size_reg helper that is shared with kfunc as well. kfunc ptr_to_mem support follows logic similar to global functions, where verification is done as if pointer is not null, even when it may be null. This leads to a simple to follow rule for writing kfunc: always check the argument pointer for NULL, except when it is PTR_TO_CTX. Also, the PTR_TO_CTX case is also only safe when the helper expecting pointer to program ctx is not exposed to other programs where same struct is not ctx type. In that case, the type check will fall through to other cases and would permit passing other types of pointers, possibly NULL at runtime. Currently, we require the size argument to be suffixed with "__sz" in the parameter name. This information is then recorded in kernel BTF and verified during function argument checking. In the future we can use BTF tagging instead, and modify the kernel function definitions. This will be a purely kernel-side change. This allows us to have some form of backwards compatibility for structures that are passed in to the kernel function with their size, and allow variable length structures to be passed in if they are accompanied by a size parameter. Signed-off-by:
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Kumar Kartikeya Dwivedi authored
Completely remove the old code for check_kfunc_call to help it work with modules, and also the callback itself. The previous commit adds infrastructure to register all sets and put them in vmlinux or module BTF, and concatenates all related sets organized by the hook and the type. Once populated, these sets remain immutable for the lifetime of the struct btf. Also, since we don't need the 'owner' module anywhere when doing check_kfunc_call, drop the 'btf_modp' module parameter from find_kfunc_desc_btf. Signed-off-by:
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Kumar Kartikeya Dwivedi authored
This patch prepares the kernel to support putting all kinds of kfunc BTF ID sets in the struct btf itself. The various kernel subsystems will make register_btf_kfunc_id_set call in the initcalls (for built-in code and modules). The 'hook' is one of the many program types, e.g. XDP and TC/SCHED_CLS, STRUCT_OPS, and 'types' are check (allowed or not), acquire, release, and ret_null (with PTR_TO_BTF_ID_OR_NULL return type). A maximum of BTF_KFUNC_SET_MAX_CNT (32) kfunc BTF IDs are permitted in a set of certain hook and type for vmlinux sets, since they are allocated on demand, and otherwise set as NULL. Module sets can only be registered once per hook and type, hence they are directly assigned. A new btf_kfunc_id_set_contains function is exposed for use in verifier, this new method is faster than the existing list searching method, and is also automatic. It also lets other code not care whether the set is unallocated or not. Note that module code can only do single register_btf_kfunc_id_set call per hook. This is why sorting is only done for in-kernel vmlinux sets, because there might be multiple sets for the same hook and type that must be concatenated, hence sorting them is required to ensure bsearch in btf_id_set_contains continues to work correctly. Next commit will update the kernel users to make use of this infrastructure. Finally, add __maybe_unused annotation for BTF ID macros for the !CONFIG_DEBUG_INFO_BTF case, so that they don't produce warnings during build time. The previous patch is also needed to provide synchronization against initialization for module BTF's kfunc_set_tab introduced here, as described below: The kfunc_set_tab pointer in struct btf is write-once (if we consider the registration phase (comprised of multiple register_btf_kfunc_id_set calls) as a single operation). In this sense, once it has been fully prepared, it isn't modified, only used for lookup (from the verifier context). For btf_vmlinux, it is initialized fully during the do_initcalls phase, which happens fairly early in the boot process, before any processes are present. This also eliminates the possibility of bpf_check being called at that point, thus relieving us of ensuring any synchronization between the registration and lookup function (btf_kfunc_id_set_contains). However, the case for module BTF is a bit tricky. The BTF is parsed, prepared, and published from the MODULE_STATE_COMING notifier callback. After this, the module initcalls are invoked, where our registration function will be called to populate the kfunc_set_tab for module BTF. At this point, BTF may be available to userspace while its corresponding module is still intializing. A BTF fd can then be passed to verifier using bpf syscall (e.g. for kfunc call insn). Hence, there is a race window where verifier may concurrently try to lookup the kfunc_set_tab. To prevent this race, we must ensure the operations are serialized, or waiting for the __init functions to complete. In the earlier registration API, this race was alleviated as verifier bpf_check_mod_kfunc_call didn't find the kfunc BTF ID until it was added by the registration function (called usually at the end of module __init function after all module resources have been initialized). If the verifier made the check_kfunc_call before kfunc BTF ID was added to the list, it would fail verification (saying call isn't allowed). The access to list was protected using a mutex. Now, it would still fail verification, but for a different reason (returning ENXIO due to the failed btf_try_get_module call in add_kfunc_call), because if the __init call is in progress the module will be in the middle of MODULE_STATE_COMING -> MODULE_STATE_LIVE transition, and the BTF_MODULE_LIVE flag for btf_module instance will not be set, so the btf_try_get_module call will fail. Signed-off-by:
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Kumar Kartikeya Dwivedi authored
While working on code to populate kfunc BTF ID sets for module BTF from its initcall, I noticed that by the time the initcall is invoked, the module BTF can already be seen by userspace (and the BPF verifier). The existing btf_try_get_module calls try_module_get which only fails if mod->state == MODULE_STATE_GOING, i.e. it can increment module reference when module initcall is happening in parallel. Currently, BTF parsing happens from MODULE_STATE_COMING notifier callback. At this point, the module initcalls have not been invoked. The notifier callback parses and prepares the module BTF, allocates an ID, which publishes it to userspace, and then adds it to the btf_modules list allowing the kernel to invoke btf_try_get_module for the BTF. However, at this point, the module has not been fully initialized (i.e. its initcalls have not finished). The code in module.c can still fail and free the module, without caring for other users. However, nothing stops btf_try_get_module from succeeding between the state transition from MODULE_STATE_COMING to MODULE_STATE_LIVE. This leads to a use-after-free issue when BPF program loads successfully in the state transition, load_module's do_init_module call fails and frees the module, and BPF program fd on close calls module_put for the freed module. Future patch has test case to verify we don't regress in this area in future. There are multiple points after prepare_coming_module (in load_module) where failure can occur and module loading can return error. We illustrate and test for the race using the last point where it can practically occur (in module __init function). An illustration of the race: CPU 0 CPU 1 load_module notifier_call(MODULE_STATE_COMING) btf_parse_module btf_alloc_id // Published to userspace list_add(&btf_mod->list, btf_modules) mod->init(...) ... ^ bpf_check | check_pseudo_btf_id | btf_try_get_module | returns true | ... ... | module __init in progress return prog_fd | ... ... V if (ret < 0) free_module(mod) ... close(prog_fd) ... bpf_prog_free_deferred module_put(used_btf.mod) // use-after-free We fix this issue by setting a flag BTF_MODULE_F_LIVE, from the notifier callback when MODULE_STATE_LIVE state is reached for the module, so that we return NULL from btf_try_get_module for modules that are not fully formed. Since try_module_get already checks that module is not in MODULE_STATE_GOING state, and that is the only transition a live module can make before being removed from btf_modules list, this is enough to close the race and prevent the bug. A later selftest patch crafts the race condition artifically to verify that it has been fixed, and that verifier fails to load program (with ENXIO). Lastly, a couple of comments: 1. Even if this race didn't exist, it seems more appropriate to only access resources (ksyms and kfuncs) of a fully formed module which has been initialized completely. 2. This patch was born out of need for synchronization against module initcall for the next patch, so it is needed for correctness even without the aforementioned race condition. The BTF resources initialized by module initcall are set up once and then only looked up, so just waiting until the initcall has finished ensures correct behavior. Fixes: 541c3bad ("bpf: Support BPF ksym variables in kernel modules") Signed-off-by:
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