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Mon, 01 Mar 2021 05:09:04 -0800 (PST) Subject: Re: [PATCH] net/core/skbuff.c: __netdev_alloc_skb fix when len is greater than KMALLOC_MAX_SIZE To: Pavel Skripkin , davem@davemloft.net, kuba@kernel.org, linmiaohe@huawei.com, Sabyrzhan Tasbolatov Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+80dccaee7c6630fa9dcf@syzkaller.appspotmail.com References: <20210226191106.554553-1-paskripkin@gmail.com> From: Eric Dumazet Message-ID: <24d966a7-ed2e-eb50-23e9-71ff2e43371f@gmail.com> Date: Mon, 1 Mar 2021 14:09:02 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <20210226191106.554553-1-paskripkin@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/26/21 8:11 PM, Pavel Skripkin wrote: > syzbot found WARNING in __alloc_pages_nodemask()[1] when order >= MAX_ORDER. > It was caused by __netdev_alloc_skb(), which doesn't check len value after adding NET_SKB_PAD. > Order will be >= MAX_ORDER and passed to __alloc_pages_nodemask() if size > KMALLOC_MAX_SIZE. > > static void *kmalloc_large_node(size_t size, gfp_t flags, int node) > { > struct page *page; > void *ptr = NULL; > unsigned int order = get_order(size); > ... > page = alloc_pages_node(node, flags, order); > ... > > [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 > Change-Id: I480a6d6f818a4c0a387db0cd3f230b68a7daeb16 > --- > net/core/skbuff.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > index 785daff48030..dc28c8f7bf5f 100644 > --- a/net/core/skbuff.c > +++ b/net/core/skbuff.c > @@ -443,6 +443,9 @@ struct sk_buff *__netdev_alloc_skb(struct net_device *dev, unsigned int len, > if (len <= SKB_WITH_OVERHEAD(1024) || > len > SKB_WITH_OVERHEAD(PAGE_SIZE) || > (gfp_mask & (__GFP_DIRECT_RECLAIM | GFP_DMA))) { > + if (len > KMALLOC_MAX_SIZE) > + return NULL; > + > skb = __alloc_skb(len, gfp_mask, SKB_ALLOC_RX, NUMA_NO_NODE); > if (!skb) > goto skb_fail; > No, please fix the offender instead. Offender tentative fix was in commit 2a80c15812372e554474b1dba0b1d8e467af295d Author: Sabyrzhan Tasbolatov Date: Tue Feb 2 15:20:59 2021 +0600 net/qrtr: restrict user-controlled length in qrtr_tun_write_iter() qrtr maintainers have to tell us what is the maximum datagram length they need to support.