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authorFlorian Westphal <fw@strlen.de>2017-11-01 20:30:49 +0100
committerSteffen Klassert <steffen.klassert@secunet.com>2017-11-02 11:53:53 +0100
commitcb79a180f2e7eb51de5a4848652893197637bccb (patch)
tree0c10afe3f7be5f2228ac3fddabf4977d14cd6119 /net/xfrm
parentMerge git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf (diff)
downloadlinux-dev-cb79a180f2e7eb51de5a4848652893197637bccb.tar.xz
linux-dev-cb79a180f2e7eb51de5a4848652893197637bccb.zip
xfrm: defer daddr pointer assignment after spi parsing
syzbot reports: BUG: KASAN: use-after-free in __xfrm_state_lookup+0x695/0x6b0 Read of size 4 at addr ffff8801d434e538 by task syzkaller647520/2991 [..] __xfrm_state_lookup+0x695/0x6b0 net/xfrm/xfrm_state.c:833 xfrm_state_lookup+0x8a/0x160 net/xfrm/xfrm_state.c:1592 xfrm_input+0x8e5/0x22f0 net/xfrm/xfrm_input.c:302 The use-after-free is the ipv4 destination address, which points to an skb head area that has been reallocated: pskb_expand_head+0x36b/0x1210 net/core/skbuff.c:1494 __pskb_pull_tail+0x14a/0x17c0 net/core/skbuff.c:1877 pskb_may_pull include/linux/skbuff.h:2102 [inline] xfrm_parse_spi+0x3d3/0x4d0 net/xfrm/xfrm_input.c:170 xfrm_input+0xce2/0x22f0 net/xfrm/xfrm_input.c:291 so the real bug is that xfrm_parse_spi() uses pskb_may_pull, but for now do smaller workaround that makes xfrm_input fetch daddr after spi parsing. Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Diffstat (limited to 'net/xfrm')
-rw-r--r--net/xfrm/xfrm_input.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/net/xfrm/xfrm_input.c b/net/xfrm/xfrm_input.c
index 8ac9d32fb79d..1c6051cb7733 100644
--- a/net/xfrm/xfrm_input.c
+++ b/net/xfrm/xfrm_input.c
@@ -265,8 +265,6 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
goto lock;
}
- daddr = (xfrm_address_t *)(skb_network_header(skb) +
- XFRM_SPI_SKB_CB(skb)->daddroff);
family = XFRM_SPI_SKB_CB(skb)->family;
/* if tunnel is present override skb->mark value with tunnel i_key */
@@ -293,6 +291,8 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
goto drop;
}
+ daddr = (xfrm_address_t *)(skb_network_header(skb) +
+ XFRM_SPI_SKB_CB(skb)->daddroff);
do {
if (skb->sp->len == XFRM_MAX_DEPTH) {
XFRM_INC_STATS(net, LINUX_MIB_XFRMINBUFFERERROR);