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Subject[PATCH] net/core/skbuff.c: __netdev_alloc_skb fix when len is greater than KMALLOC_MAX_SIZE
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

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) ||
(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;
 \ /
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