diff options
| author | Florian Westphal <fw@strlen.de> | 2024-02-16 12:36:57 +0100 |
|---|---|---|
| committer | Paolo Abeni <pabeni@redhat.com> | 2024-02-20 12:21:40 +0100 |
| commit | 219eee9c0d16f1b754a8b85275854ab17df0850a (patch) | |
| tree | e4ef2e571ada7d52b9551340767cf78b3a0a522a | |
| parent | 5d4cc87414c5d11345c4b11d61377d351b5c28a2 (diff) | |
net: skbuff: add overflow debug check to pull/push helpers
syzbot managed to trigger following splat:
BUG: KASAN: use-after-free in __skb_flow_dissect+0x4a3b/0x5e50
Read of size 1 at addr ffff888208a4000e by task a.out/2313
[..]
__skb_flow_dissect+0x4a3b/0x5e50
__skb_get_hash+0xb4/0x400
ip_tunnel_xmit+0x77e/0x26f0
ipip_tunnel_xmit+0x298/0x410
..
Analysis shows that the skb has a valid ->head, but bogus ->data
pointer.
skb->data gets its bogus value via the neigh layer, which does:
1556 __skb_pull(skb, skb_network_offset(skb));
... and the skb was already dodgy at this point:
skb_network_offset(skb) returns a negative value due to an
earlier overflow of skb->network_header (u16). __skb_pull thus
"adjusts" skb->data by a huge offset, pointing outside skb->head
area.
Allow debug builds to splat when we try to pull/push more than
INT_MAX bytes.
After this, the syzkaller reproducer yields a more precise splat
before the flow dissector attempts to read off skb->data memory:
WARNING: CPU: 5 PID: 2313 at include/linux/skbuff.h:2653 neigh_connected_output+0x28e/0x400
ip_finish_output2+0xb25/0xed0
iptunnel_xmit+0x4ff/0x870
ipgre_xmit+0x78e/0xbb0
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240216113700.23013-1-fw@strlen.de
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
| -rw-r--r-- | include/linux/skbuff.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index e3a2ed5d09ad..28c7cb7ce251 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -2684,6 +2684,8 @@ static inline void skb_put_u8(struct sk_buff *skb, u8 val) void *skb_push(struct sk_buff *skb, unsigned int len); static inline void *__skb_push(struct sk_buff *skb, unsigned int len) { + DEBUG_NET_WARN_ON_ONCE(len > INT_MAX); + skb->data -= len; skb->len += len; return skb->data; @@ -2692,6 +2694,8 @@ static inline void *__skb_push(struct sk_buff *skb, unsigned int len) void *skb_pull(struct sk_buff *skb, unsigned int len); static inline void *__skb_pull(struct sk_buff *skb, unsigned int len) { + DEBUG_NET_WARN_ON_ONCE(len > INT_MAX); + skb->len -= len; if (unlikely(skb->len < skb->data_len)) { #if defined(CONFIG_DEBUG_NET) @@ -2716,6 +2720,8 @@ void *__pskb_pull_tail(struct sk_buff *skb, int delta); static inline enum skb_drop_reason pskb_may_pull_reason(struct sk_buff *skb, unsigned int len) { + DEBUG_NET_WARN_ON_ONCE(len > INT_MAX); + if (likely(len <= skb_headlen(skb))) return SKB_NOT_DROPPED_YET; |