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bpf: Don't EFAULT for getsockopt with optval=NULL

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Some socket options do getsockopt with optval=NULL to estimate the size
of the final buffer (which is returned via optlen). This breaks BPF
getsockopt assumptions about permitted optval buffer size. Let's enforce
these assumptions only when non-NULL optval is provided.

Fixes: 0d01da6afc ("bpf: implement getsockopt and setsockopt hooks")
Reported-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/ZD7Js4fj5YyI2oLd@google.com/T/#mb68daf700f87a9244a15d01d00c3f0e5b08f49f7
Link: https://lore.kernel.org/bpf/20230418225343.553806-2-sdf@google.com
This commit is contained in:
Stanislav Fomichev 2023-04-18 15:53:38 -07:00 committed by Daniel Borkmann
parent 02e93e0475
commit 00e74ae086
1 changed files with 6 additions and 3 deletions
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9
kernel/bpf/cgroup.c
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@ -1921,14 +1921,17 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level,
if (ret < 0)
goto out;
if (ctx.optlen > max_optlen || ctx.optlen < 0) {
if (optval && (ctx.optlen > max_optlen || ctx.optlen < 0)) {
ret = -EFAULT;
goto out;
}
if (ctx.optlen != 0) {
if (copy_to_user(optval, ctx.optval, ctx.optlen) ||
put_user(ctx.optlen, optlen)) {
if (optval && copy_to_user(optval, ctx.optval, ctx.optlen)) {
ret = -EFAULT;
goto out;
}
if (put_user(ctx.optlen, optlen)) {
ret = -EFAULT;
goto out;
}