Re: [PATCH v4] net/qrtr: fix __netdev_alloc_skb call

[Alexander Lobakin]

From: Pavel Skripkin <paskripkin@xxxxxxxxx>
Date: Mon, 1 Mar 2021 02:22:40 +0300

> 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@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Pavel Skripkin <paskripkin@xxxxxxxxx>

Acked-by: Alexander Lobakin <alobakin@xxxxx>

Thanks!

> ---
>  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

Al