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From:   Pavel Skripkin <paskripkin@gmail.com>
To:     alobakin@pm.me
Cc:     linmiaohe@huawei.com, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        syzbot+80dccaee7c6630fa9dcf@syzkaller.appspotmail.com,
        Pavel Skripkin <paskripkin@gmail.com>
Subject: [PATCH v4] net/qrtr: fix __netdev_alloc_skb call
Date:   Mon,  1 Mar 2021 02:22:40 +0300
Message-Id: <20210228232240.972205-1-paskripkin@gmail.com>
In-Reply-To: <20210228201000.13606-1-alobakin@pm.me>
References: <20210228201000.13606-1-alobakin@pm.me>
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syzbot found WARNING in __alloc_pages_nodemask()[1] when order >= MAX_ORDER.
It was caused by a huge length value passed from userspace to qrtr_tun_write_iter(),
which tries to allocate skb. Since the value comes from the untrusted source 
there is no need to raise a warning in __alloc_pages_nodemask().

[1] WARNING in __alloc_pages_nodemask+0x5f8/0x730 mm/page_alloc.c:5014
Call Trace:
 __alloc_pages include/linux/gfp.h:511 [inline]
 __alloc_pages_node include/linux/gfp.h:524 [inline]
 alloc_pages_node include/linux/gfp.h:538 [inline]
 kmalloc_large_node+0x60/0x110 mm/slub.c:3999
 __kmalloc_node_track_caller+0x319/0x3f0 mm/slub.c:4496
 __kmalloc_reserve net/core/skbuff.c:150 [inline]
 __alloc_skb+0x4e4/0x5a0 net/core/skbuff.c:210
 __netdev_alloc_skb+0x70/0x400 net/core/skbuff.c:446
 netdev_alloc_skb include/linux/skbuff.h:2832 [inline]
 qrtr_endpoint_post+0x84/0x11b0 net/qrtr/qrtr.c:442
 qrtr_tun_write_iter+0x11f/0x1a0 net/qrtr/tun.c:98
 call_write_iter include/linux/fs.h:1901 [inline]
 new_sync_write+0x426/0x650 fs/read_write.c:518
 vfs_write+0x791/0xa30 fs/read_write.c:605
 ksys_write+0x12d/0x250 fs/read_write.c:658
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported-by: syzbot+80dccaee7c6630fa9dcf@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
---
 net/qrtr/qrtr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c
index b34358282f37..82d2eb8c21d1 100644
--- a/net/qrtr/qrtr.c
+++ b/net/qrtr/qrtr.c
@@ -439,7 +439,7 @@ int qrtr_endpoint_post(struct qrtr_endpoint *ep, const void *data, size_t len)
 	if (len == 0 || len & 3)
 		return -EINVAL;
 
-	skb = netdev_alloc_skb(NULL, len);
+	skb = __netdev_alloc_skb(NULL, len, GFP_ATOMIC | __GFP_NOWARN);
 	if (!skb)
 		return -ENOMEM;
 
-- 
2.25.1