linux-kernel - [PATCH] net: core: sk_buff: zero-fill skb->data in __alloc

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Message-Id: <20210410095149.3708143-1-phil@philpotter.co.uk>
Date:   Sat, 10 Apr 2021 10:51:49 +0100
From:   Phillip Potter <phil@...lpotter.co.uk>
To:     davem@...emloft.net
Cc:     kuba@...nel.org, willemb@...gle.com, linmiaohe@...wei.com,
        edumazet@...gle.com, linyunsheng@...wei.com, alobakin@...me,
        elver@...gle.com, gnault@...hat.com, dseok.yi@...sung.com,
        viro@...iv.linux.org.uk, vladimir.oltean@....com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] net: core: sk_buff: zero-fill skb->data in __alloc_skb function

Zero-fill skb->data in __alloc_skb function of net/core/skbuff.c,
up to start of struct skb_shared_info bytes. Fixes a KMSAN-found
uninit-value bug reported by syzbot at:
https://syzkaller.appspot.com/bug?id=abe95dc3e3e9667fc23b8d81f29ecad95c6f106f

Reported-by: syzbot+2e406a9ac75bb71d4b7a@...kaller.appspotmail.com
Signed-off-by: Phillip Potter <phil@...lpotter.co.uk>
---
 net/core/skbuff.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 785daff48030..9ac26cdb5417 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -215,6 +215,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
 	 * to allow max possible filling before reallocation.
 	 */
 	size = SKB_WITH_OVERHEAD(ksize(data));
+	memset(data, 0, size);
 	prefetchw(data + size);
 
 	/*
-- 
2.30.2