bpf: Explicitly check accesses to bpf_sock_addr
[ Upstream commit 6fabca2fc94d33cdf7ec102058983b086293395f ]
Syzkaller found a kernel warning on the following sock_addr program:
0: r0 = 0
1: r2 = *(u32 *)(r1 +60)
2: exit
which triggers:
verifier bug: error during ctx access conversion (0)
This is happening because offset 60 in bpf_sock_addr corresponds to an
implicit padding of 4 bytes, right after msg_src_ip4. Access to this
padding isn't rejected in sock_addr_is_valid_access and it thus later
fails to convert the access.
This patch fixes it by explicitly checking the various fields of
bpf_sock_addr in sock_addr_is_valid_access.
I checked the other ctx structures and is_valid_access functions and
didn't find any other similar cases. Other cases of (properly handled)
padding are covered in new tests in a subsequent patch.
BUG=b/456103589
TEST=presubmit
RELEASE_NOTE=Fixed CVE-2025-40078 in the Linux kernel.
cos-patch: security-moderate
Fixes: 1cedee13d25a ("bpf: Hooks for sys_sendmsg")
Reported-by: syzbot+136ca59d411f92e821b7@syzkaller.appspotmail.com
Change-Id: Ib106f2a0dd5d8083d556ec36b5cf840dc7762489
Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Closes: https://syzkaller.appspot.com/bug?extid=136ca59d411f92e821b7
Link: https://lore.kernel.org/bpf/b58609d9490649e76e584b0361da0abd3c2c1779.1758094761.git.paul.chaignon@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Robert Velasquez <rdvelasquez@google.com>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/116862
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Dom Huh <domhuh@google.com>
1 file changed
