commit 6f06a2c45d8d714ea3b11a360b4a7191e52acaa4 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: James Hogan <james.hogan@xxxxxxxxxx> Cc: Markos Chandras <markos.chandras@xxxxxxxxxx> Cc: Paul Burton <paul.burton@xxxxxxxxxx> Cc: Leonid Yegoshin <leonid.yegoshin@xxxxxxxxxx> Cc: linux-mips@xxxxxxxxxxxxxx Patchwork: https://patchwork.linux-mips.org/patch/10843/ Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx> [james.hogan@xxxxxxxxxx: backport] Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx> --- arch/mips/include/asm/uaccess.h | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/arch/mips/include/asm/uaccess.h b/arch/mips/include/asm/uaccess.h index bf8b32450ef6..d8f7394275af 100644 --- a/arch/mips/include/asm/uaccess.h +++ b/arch/mips/include/asm/uaccess.h @@ -1095,9 +1095,15 @@ extern size_t __copy_in_user_eva(void *__to, const void *__from, size_t __n); __cu_to = (to); \ __cu_from = (from); \ __cu_len = (n); \ - might_fault(); \ - __cu_len = __invoke_copy_from_user(__cu_to, __cu_from, \ - __cu_len); \ + if (segment_eq(get_fs(), get_ds())) { \ + __cu_len = __invoke_copy_from_kernel(__cu_to, \ + __cu_from, \ + __cu_len); \ + } else { \ + might_fault(); \ + __cu_len = __invoke_copy_from_user(__cu_to, __cu_from, \ + __cu_len); \ + } \ __cu_len; \ }) -- 2.4.10
