5.4-stable review patch. If anyone has any objections, please let me know.
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From: Paul Chaignon paul.chaignon@gmail.com
[ Upstream commit ead3d7b2b6afa5ee7958620c4329982a7d9c2b78 ]
flow_dissector_is_valid_access doesn't check that the context access is aligned. As a consequence, an unaligned access within one of the exposed field is considered valid and later rejected by flow_dissector_convert_ctx_access when we try to convert it.
The later rejection is problematic because it's reported as a verifier bug with a kernel warning and doesn't point to the right instruction in verifier logs.
Fixes: d58e468b1112 ("flow_dissector: implements flow dissector BPF hook") Reported-by: syzbot+ccac90e482b2a81d74aa@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=ccac90e482b2a81d74aa Signed-off-by: Paul Chaignon paul.chaignon@gmail.com Acked-by: Yonghong Song yonghong.song@linux.dev Acked-by: Eduard Zingerman eddyz87@gmail.com Link: https://lore.kernel.org/r/cc1b036be484c99be45eddf48bd78cc6f72839b1.175403960... Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/core/filter.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/net/core/filter.c b/net/core/filter.c index e6ec6f013ec0..fd18497977bd 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -7282,6 +7282,9 @@ static bool flow_dissector_is_valid_access(int off, int size, if (off < 0 || off >= sizeof(struct __sk_buff)) return false;
+ if (off % size != 0) + return false; + if (type == BPF_WRITE) return false;