Commit 029692a0 authored by James Hogan's avatar James Hogan Committed by Luis Henriques

MIPS: uaccess: Take EVA into account in __copy_from_user()

commit 6f06a2c4 upstream.

When EVA is in use, __copy_from_user() was unconditionally using the EVA
instructions to read the user address space, however this can also be
used for kernel access. If the address isn't a valid user address it
will cause an address error or TLB exception, and if it is then user
memory may be read instead of kernel memory.

For example in the following stack trace from Linux v3.10 (changes since
then will prevent this particular one still happening) kernel_sendmsg()
set the user address limit to KERNEL_DS, and tcp_sendmsg() goes on to
use __copy_from_user() with a kernel address in KSeg0.

[<8002d434>] __copy_fromuser_common+0x10c/0x254
[<805710e0>] tcp_sendmsg+0x5f4/0xf00
[<804e8e3c>] sock_sendmsg+0x78/0xa0
[<804e8f28>] kernel_sendmsg+0x24/0x38
[<804ee0f8>] sock_no_sendpage+0x70/0x7c
[<8017c820>] pipe_to_sendpage+0x80/0x98
[<8017c6b0>] splice_from_pipe_feed+0xa8/0x198
[<8017cc54>] __splice_from_pipe+0x4c/0x8c
[<8017e844>] splice_from_pipe+0x58/0x78
[<8017e884>] generic_splice_sendpage+0x20/0x2c
[<8017d690>] do_splice_from+0xb4/0x110
[<8017d710>] direct_splice_actor+0x24/0x30
[<8017d394>] splice_direct_to_actor+0xd8/0x208
[<8017d51c>] do_splice_direct+0x58/0x7c
[<8014eaf4>] do_sendfile+0x1dc/0x39c
[<8014f82c>] SyS_sendfile+0x90/0xf8

Add the eva_kernel_access() check in __copy_from_user() like the one in
copy_from_user().
Signed-off-by: default avatarJames Hogan <james.hogan@imgtec.com>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Leonid Yegoshin <leonid.yegoshin@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10843/Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
[james.hogan@imgtec.com: backport]
Signed-off-by: default avatarJames Hogan <james.hogan@imgtec.com>
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent 4692cf46
...@@ -1092,9 +1092,15 @@ extern size_t __copy_in_user_eva(void *__to, const void *__from, size_t __n); ...@@ -1092,9 +1092,15 @@ extern size_t __copy_in_user_eva(void *__to, const void *__from, size_t __n);
__cu_to = (to); \ __cu_to = (to); \
__cu_from = (from); \ __cu_from = (from); \
__cu_len = (n); \ __cu_len = (n); \
might_fault(); \ if (segment_eq(get_fs(), get_ds())) { \
__cu_len = __invoke_copy_from_user(__cu_to, __cu_from, \ __cu_len = __invoke_copy_from_kernel(__cu_to, \
__cu_len); \ __cu_from, \
__cu_len); \
} else { \
might_fault(); \
__cu_len = __invoke_copy_from_user(__cu_to, __cu_from, \
__cu_len); \
} \
__cu_len; \ __cu_len; \
}) })
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment