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Date: Fri, 24 Oct 2025 17:39:01 +0100
From: Simon Horman <horms@kernel.org>
To: Ranganath V N <vnranganath.20@gmail.com>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>,
	Xin Long <lucien.xin@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	linux-sctp@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
	syzbot+d101e12bccd4095460e7@syzkaller.appspotmail.com
Subject: Re: [PATCH v2] net: sctp: fix KMSAN uninit-value in sctp_inq_pop
Message-ID: <aPurpdMe6BHfSHEH@horms.kernel.org>
References: <20251024-kmsan_fix-v2-1-dc393cfb9071@gmail.com>
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In-Reply-To: <20251024-kmsan_fix-v2-1-dc393cfb9071@gmail.com>

On Fri, Oct 24, 2025 at 05:14:17PM +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
> Fixes: https://syzkaller.appspot.com/bug?extid=d101e12bccd4095460e7

Hi,

Thanks for your patch.

Unfortunately, this is not the correct format for a fixes tag.
A fixes tag should reference the commit where the bug
was introduced into the tree. In this case, perhaps that
is the beginning of git history. If so:

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")

I think the URL you provide is appropriate for a Closed tag.

Closes: https://syzkaller.appspot.com/bug?extid=d101e12bccd4095460e7

See https://docs.kernel.org/process/submitting-patches.html

> Suggested-by: Xin Long <lucien.xin@gmail.com>
> Signed-off-by: Ranganath V N <vnranganath.20@gmail.com>
> ---
> KMSAN reported an uninitialized-value access in sctp_inq_pop
> ---
> Changes in v2:
> - changes in commit message as per the code changes.
> - fixed as per the suggestion.
> - Link to v1: https://lore.kernel.org/r/20251023-kmsan_fix-v1-1-d08c18db8877@gmail.com

...