3.2.55-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Daniel Borkmann <dborkman@xxxxxxxxxx>
[ Upstream commit 4d231b76eef6c4a6bd9c96769e191517765942cb ]
While commit 30a584d944fb fixes datagram interface in LLC, a use
after free bug has been introduced for SOCK_STREAM sockets that do
not make use of MSG_PEEK.
The flow is as follow ...
if (!(flags & MSG_PEEK)) {
...
sk_eat_skb(sk, skb, false);
...
}
...
if (used + offset < skb->len)
continue;
... where sk_eat_skb() calls __kfree_skb(). Therefore, cache
original length and work on skb_len to check partial reads.
Fixes: 30a584d944fb ("[LLX]: SOCK_DGRAM interface fixes")
Signed-off-by: Daniel Borkmann <dborkman@xxxxxxxxxx>
Cc: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
net/llc/af_llc.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c
index 99a60d5..f432d7b 100644
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -715,7 +715,7 @@ static int llc_ui_recvmsg(struct kiocb *iocb, struct socket *sock,
struct llc_sock *llc = llc_sk(sk);
size_t copied = 0;
u32 peek_seq = 0;
- u32 *seq;
+ u32 *seq, skb_len;
unsigned long used;
int target; /* Read at least this many bytes */
long timeo;
@@ -813,6 +813,7 @@ static int llc_ui_recvmsg(struct kiocb *iocb, struct socket *sock,
}
continue;
found_ok_skb:
+ skb_len = skb->len;
/* Ok so how much can we use? */
used = skb->len - offset;
if (len < used)
@@ -843,7 +844,7 @@ static int llc_ui_recvmsg(struct kiocb *iocb, struct socket *sock,
}
/* Partial read */
- if (used + offset < skb->len)
+ if (used + offset < skb_len)
continue;
} while (len > 0);
--
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