Re: [PATCH v3] net: sctp: fix KMSAN uninit-value in sctp_inq_pop

On Sun, Oct 26, 2025 at 10:03:12PM +0530, Ranganath V N wrote:

Fix an issue detected by syzbot:

KMSAN reported an uninitialized-value access in sctp_inq_pop
BUG: KMSAN: uninit-value in sctp_inq_pop

The issue is actually caused by skb trimming via sk_filter() in sctp_rcv().
In the reproducer, skb->len becomes 1 after sk_filter(), which bypassed the
original check:

        if (skb->len < sizeof(struct sctphdr) + sizeof(struct sctp_chunkhdr) +
                       skb_transport_offset(skb))
To handle this safely, a new check should be performed after sk_filter().

Reported-by: syzbot+d101e12bccd4095460e7@syzkaller.appspotmail.com
Tested-by: syzbot+d101e12bccd4095460e7@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=d101e12bccd4095460e7
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Suggested-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Ranganath V N <redacted>
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KMSAN reported an uninitialized-value access in sctp_inq_pop
---
Changes in v3:
- fixes the patch format like fixes and closes tags.
- Link to v2: https://lore.kernel.org/r/20251024-kmsan_fix-v2-1-dc393cfb9071@gmail.com (local)

Thanks for the update. This version looks good to me.
And I assume it is for net.

Reviewed-by: Simon Horman <horms@kernel.org>