From 4d231b76eef6c4a6bd9c96769e191517765942cb Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Mon, 30 Dec 2013 23:40:50 +0100 Subject: [PATCH] net: llc: fix use after free in llc_ui_recvmsg 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 Cc: Stephen Hemminger Cc: Arnaldo Carvalho de Melo Signed-off-by: David S. Miller --- 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 7b01b9f5846c..c71b699eb555 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, unsigned long cpu_flags; 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; @@ -812,6 +812,7 @@ 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) @@ -844,7 +845,7 @@ 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); -- 2.39.5