Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf

Daniel Borkmann says:

====================
pull-request: bpf 2021-06-02

The following pull-request contains BPF updates for your *net* tree.

We've added 2 non-merge commits during the last 7 day(s) which contain
a total of 4 files changed, 19 insertions(+), 24 deletions(-).

The main changes are:

1) Fix pahole BTF generation when ccache is used, from Javier Martinez Canillas.

2) Fix BPF lockdown hooks in bpf_probe_read_kernel{,_str}() helpers which caused
   a deadlock from bcc programs, triggered OOM killer from audit side and didn't
   work generally with SELinux policy rules due to pointing to wrong task struct,
   from Daniel Borkmann.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

kernel/bpf/helpers.c

@@ -14,6 +14,7 @@
 #include <linux/jiffies.h>
 #include <linux/pid_namespace.h>
 #include <linux/proc_ns.h>
+#include <linux/security.h>
 
 #include "../../lib/kstrtox.h"
 
@@ -1069,11 +1070,13 @@ bpf_base_func_proto(enum bpf_func_id func_id)
 	case BPF_FUNC_probe_read_user:
 		return &bpf_probe_read_user_proto;
 	case BPF_FUNC_probe_read_kernel:
-		return &bpf_probe_read_kernel_proto;
+		return security_locked_down(LOCKDOWN_BPF_READ) < 0 ?
+		       NULL : &bpf_probe_read_kernel_proto;
 	case BPF_FUNC_probe_read_user_str:
 		return &bpf_probe_read_user_str_proto;
 	case BPF_FUNC_probe_read_kernel_str:
-		return &bpf_probe_read_kernel_str_proto;
+		return security_locked_down(LOCKDOWN_BPF_READ) < 0 ?
+		       NULL : &bpf_probe_read_kernel_str_proto;
 	case BPF_FUNC_snprintf_btf:
 		return &bpf_snprintf_btf_proto;
 	case BPF_FUNC_snprintf:

kernel/trace/bpf_trace.c

@@ -215,16 +215,11 @@ const struct bpf_func_proto bpf_probe_read_user_str_proto = {
 static __always_inline int
 bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr)
 {
-	int ret = security_locked_down(LOCKDOWN_BPF_READ);
+	int ret;
 
-	if (unlikely(ret < 0))
-		goto fail;
 	ret = copy_from_kernel_nofault(dst, unsafe_ptr, size);
 	if (unlikely(ret < 0))
-		goto fail;
-	return ret;
-fail:
-	memset(dst, 0, size);
+		memset(dst, 0, size);
 	return ret;
 }
 
@@ -246,10 +241,7 @@ const struct bpf_func_proto bpf_probe_read_kernel_proto = {
 static __always_inline int
 bpf_probe_read_kernel_str_common(void *dst, u32 size, const void *unsafe_ptr)
 {
-	int ret = security_locked_down(LOCKDOWN_BPF_READ);
-
-	if (unlikely(ret < 0))
-		goto fail;
+	int ret;
 
 	/*
 	 * The strncpy_from_kernel_nofault() call will likely not fill the
@@ -262,11 +254,7 @@ bpf_probe_read_kernel_str_common(void *dst, u32 size, const void *unsafe_ptr)
 	 */
 	ret = strncpy_from_kernel_nofault(dst, unsafe_ptr, size);
 	if (unlikely(ret < 0))
-		goto fail;
-
-	return ret;
-fail:
-	memset(dst, 0, size);
+		memset(dst, 0, size);
 	return ret;
 }
 
@@ -1011,16 +999,20 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	case BPF_FUNC_probe_read_user:
 		return &bpf_probe_read_user_proto;
 	case BPF_FUNC_probe_read_kernel:
-		return &bpf_probe_read_kernel_proto;
+		return security_locked_down(LOCKDOWN_BPF_READ) < 0 ?
+		       NULL : &bpf_probe_read_kernel_proto;
 	case BPF_FUNC_probe_read_user_str:
 		return &bpf_probe_read_user_str_proto;
 	case BPF_FUNC_probe_read_kernel_str:
-		return &bpf_probe_read_kernel_str_proto;
+		return security_locked_down(LOCKDOWN_BPF_READ) < 0 ?
+		       NULL : &bpf_probe_read_kernel_str_proto;
 #ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
 	case BPF_FUNC_probe_read:
-		return &bpf_probe_read_compat_proto;
+		return security_locked_down(LOCKDOWN_BPF_READ) < 0 ?
+		       NULL : &bpf_probe_read_compat_proto;
 	case BPF_FUNC_probe_read_str:
-		return &bpf_probe_read_compat_str_proto;
+		return security_locked_down(LOCKDOWN_BPF_READ) < 0 ?
+		       NULL : &bpf_probe_read_compat_str_proto;
 #endif
 #ifdef CONFIG_CGROUPS
 	case BPF_FUNC_get_current_cgroup_id:

scripts/Makefile.modfinal

@@ -59,7 +59,7 @@ quiet_cmd_ld_ko_o = LD [M]  $@
 quiet_cmd_btf_ko = BTF [M] $@
       cmd_btf_ko = 							\
 	if [ -f vmlinux ]; then						\
-		LLVM_OBJCOPY=$(OBJCOPY) $(PAHOLE) -J --btf_base vmlinux $@; \
+		LLVM_OBJCOPY="$(OBJCOPY)" $(PAHOLE) -J --btf_base vmlinux $@; \
 	else								\
 		printf "Skipping BTF generation for %s due to unavailability of vmlinux\n" $@ 1>&2; \
 	fi;

scripts/link-vmlinux.sh

@@ -240,7 +240,7 @@ gen_btf()
 	fi
 
 	info "BTF" ${2}
-	LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${extra_paholeopt} ${1}
+	LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${extra_paholeopt} ${1}
 
 	# Create ${2} which contains just .BTF section but no symbols. Add
 	# SHF_ALLOC because .BTF will be part of the vmlinux image. --strip-all