From 51e5ad549c43b557c7da1e4d1a1dcf061b4a5f6c Mon Sep 17 00:00:00 2001 From: Ranganath V N Date: Sun, 26 Oct 2025 22:03:12 +0530 Subject: [PATCH] net: sctp: fix KMSAN uninit-value in sctp_inq_pop 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 Signed-off-by: Ranganath V N Reviewed-by: Simon Horman Link: https://patch.msgid.link/20251026-kmsan_fix-v3-1-2634a409fa5f@gmail.com Signed-off-by: Paolo Abeni --- net/sctp/input.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/sctp/input.c b/net/sctp/input.c index 7e99894778d4..e119e460ccde 100644 --- a/net/sctp/input.c +++ b/net/sctp/input.c @@ -190,7 +190,7 @@ int sctp_rcv(struct sk_buff *skb) goto discard_release; nf_reset_ct(skb); - if (sk_filter(sk, skb)) + if (sk_filter(sk, skb) || skb->len < sizeof(struct sctp_chunkhdr)) goto discard_release; /* Create an SCTP packet structure. */ -- 2.47.3