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[5.10,026/120] bpf, cgroup: Fix optlen WARN_ON_ONCE toctou

Message ID 20210208145819.440605452@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg KH Feb. 8, 2021, 3 p.m. UTC 
From: Loris Reiff <loris.reiff@liblor.ch>

[ 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>
---
 kernel/bpf/cgroup.c | 5 +++++
 1 file changed, 5 insertions(+)
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Patch

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 96555a8a2c545..6ec8f02f463b6 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -1442,6 +1442,11 @@  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;