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bpf, cgroup: Fix optlen WARN_ON_ONCE toctou

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[ Upstream commit bb8b81e396f7afbe7c50d789e2107512274d2a35 ]

A toctou issue in `__cgroup_bpf_run_filter_getsockopt` can trigger a
WARN_ON_ONCE in a check of `copy_from_user`.

`*optlen` is checked to be non-negative in the individual getsockopt
functions beforehand. Changing `*optlen` in a race to a negative value
will result in a `copy_from_user(ctx.optval, optval, ctx.optlen)` with
`ctx.optlen` being a negative integer.

Fixes: 0d01da6afc54 ("bpf: implement getsockopt and setsockopt hooks")
Signed-off-by: Loris Reiff <loris.reiff@liblor.ch>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20210122164232.61770-1-loris.reiff@liblor.ch
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Loris Reiff 2021-01-22 17:42:31 +01:00 committed by Greg Kroah-Hartman
parent 4921f81ce6
commit 9146fffc5d
1 changed files with 5 additions and 0 deletions
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5
kernel/bpf/cgroup.c
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@ -1109,6 +1109,11 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level,
goto out;
}
if (ctx.optlen < 0) {
ret = -EFAULT;
goto out;
}
if (copy_from_user(ctx.optval, optval,
min(ctx.optlen, max_optlen)) != 0) {
ret = -EFAULT;