diff options
| author | Florian Westphal <fw@strlen.de> | 2017-11-01 20:30:49 +0100 |
|---|---|---|
| committer | Steffen Klassert <steffen.klassert@secunet.com> | 2017-11-02 11:53:53 +0100 |
| commit | cb79a180f2e7eb51de5a4848652893197637bccb (patch) | |
| tree | 0c10afe3f7be5f2228ac3fddabf4977d14cd6119 | |
| parent | 74784da82ff74379d0583a3ffe42835888705ac7 (diff) | |
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>
| -rw-r--r-- | net/xfrm/xfrm_input.c | 4 |
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); |