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From: Edward Adam Davis <eadavis@qq.com>
To: syzbot+f770ce3566e60e5573ac@syzkaller.appspotmail.com
Cc: davem@davemloft.net,
	edumazet@google.com,
	kuba@kernel.org,
	linux-hams@vger.kernel.org,
	linux-kernel@vger.kernel.org,
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	ralf@linux-mips.org,
	syzkaller-bugs@googlegroups.com
Subject: [PATCH] skbuff: fix uninit-value in nr_route_frame
Date: Sun,  3 Mar 2024 21:23:59 +0800
In-Reply-To: <000000000000b69bf20612bf586e@google.com>
References: <000000000000b69bf20612bf586e@google.com>
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[Syzbot reported]
BUG: KMSAN: uninit-value in nr_route_frame+0x4a9/0xfc0 net/netrom/nr_route.c:787
 nr_route_frame+0x4a9/0xfc0 net/netrom/nr_route.c:787
 nr_xmit+0x5a/0x1c0 net/netrom/nr_dev.c:144
 __netdev_start_xmit include/linux/netdevice.h:4980 [inline]
 netdev_start_xmit include/linux/netdevice.h:4994 [inline]
 xmit_one net/core/dev.c:3547 [inline]
 dev_hard_start_xmit+0x244/0xa10 net/core/dev.c:3563
 __dev_queue_xmit+0x33ed/0x51c0 net/core/dev.c:4351
 dev_queue_xmit include/linux/netdevice.h:3171 [inline]
 raw_sendmsg+0x64e/0xc10 net/ieee802154/socket.c:299
 ieee802154_sock_sendmsg+0x91/0xc0 net/ieee802154/socket.c:96
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0x9c2/0xd60 net/socket.c:2584
 ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2638
 __sys_sendmsg net/socket.c:2667 [inline]
 __do_sys_sendmsg net/socket.c:2676 [inline]
 __se_sys_sendmsg net/socket.c:2674 [inline]
 __x64_sys_sendmsg+0x307/0x490 net/socket.c:2674
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:3819 [inline]
 slab_alloc_node mm/slub.c:3860 [inline]
 kmem_cache_alloc_node+0x5cb/0xbc0 mm/slub.c:3903
 kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:560
 __alloc_skb+0x352/0x790 net/core/skbuff.c:651
 alloc_skb include/linux/skbuff.h:1296 [inline]
 alloc_skb_with_frags+0xc8/0xbd0 net/core/skbuff.c:6394
 sock_alloc_send_pskb+0xa80/0xbf0 net/core/sock.c:2783
 sock_alloc_send_skb include/net/sock.h:1855 [inline]
 raw_sendmsg+0x367/0xc10 net/ieee802154/socket.c:282
 ieee802154_sock_sendmsg+0x91/0xc0 net/ieee802154/socket.c:96
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0x9c2/0xd60 net/socket.c:2584
 ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2638
 __sys_sendmsg net/socket.c:2667 [inline]
 __do_sys_sendmsg net/socket.c:2676 [inline]
 __se_sys_sendmsg net/socket.c:2674 [inline]
 __x64_sys_sendmsg+0x307/0x490 net/socket.c:2674
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

[Fix]
Let's clear all skb data at alloc time.

Reported-and-tested-by: syzbot+f770ce3566e60e5573ac@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
---
 net/core/skbuff.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index edbbef563d4d..5ca5a608daec 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -656,6 +656,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
 	 * to allow max possible filling before reallocation.
 	 */
 	prefetchw(data + SKB_WITH_OVERHEAD(size));
+	memset(data, 0, size);
 
 	/*
 	 * Only clear those fields we need to clear, not those that we will
-- 
2.43.0