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authorMiklos Szeredi <mszeredi@suse.cz>2008-11-09 15:23:57 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2008-11-09 11:17:33 -0800
commit6209344f5a3795d34b7f2c0061f49802283b6bdd (patch)
tree5c037ddbb8caac17b0c6101c9ab86387df106d41 /net/unix/af_unix.c
parent058e3739f6b0753696db1952378de9e8d2a11735 (diff)
net: unix: fix inflight counting bug in garbage collector
Previously I assumed that the receive queues of candidates don't change during the GC. This is only half true, nothing can be received from the queues (see comment in unix_gc()), but buffers could be added through the other half of the socket pair, which may still have file descriptors referring to it. This can result in inc_inflight_move_tail() erronously increasing the "inflight" counter for a unix socket for which dec_inflight() wasn't previously called. This in turn can trigger the "BUG_ON(total_refs < inflight_refs)" in a later garbage collection run. Fix this by only manipulating the "inflight" counter for sockets which are candidates themselves. Duplicating the file references in unix_attach_fds() is also needed to prevent a socket becoming a candidate for GC while the skb that contains it is not yet queued. Reported-by: Andrea Bittau <a.bittau@cs.ucl.ac.uk> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> CC: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'net/unix/af_unix.c')
-rw-r--r--net/unix/af_unix.c31
1 files changed, 24 insertions, 7 deletions
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 4d3c6071b9a4..eb90f77bb0e2 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1302,14 +1302,23 @@ static void unix_destruct_fds(struct sk_buff *skb)
sock_wfree(skb);
}
-static void unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
+static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
{
int i;
+
+ /*
+ * Need to duplicate file references for the sake of garbage
+ * collection. Otherwise a socket in the fps might become a
+ * candidate for GC while the skb is not yet queued.
+ */
+ UNIXCB(skb).fp = scm_fp_dup(scm->fp);
+ if (!UNIXCB(skb).fp)
+ return -ENOMEM;
+
for (i=scm->fp->count-1; i>=0; i--)
unix_inflight(scm->fp->fp[i]);
- UNIXCB(skb).fp = scm->fp;
skb->destructor = unix_destruct_fds;
- scm->fp = NULL;
+ return 0;
}
/*
@@ -1368,8 +1377,11 @@ static int unix_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock,
goto out;
memcpy(UNIXCREDS(skb), &siocb->scm->creds, sizeof(struct ucred));
- if (siocb->scm->fp)
- unix_attach_fds(siocb->scm, skb);
+ if (siocb->scm->fp) {
+ err = unix_attach_fds(siocb->scm, skb);
+ if (err)
+ goto out_free;
+ }
unix_get_secdata(siocb->scm, skb);
skb_reset_transport_header(skb);
@@ -1538,8 +1550,13 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
size = min_t(int, size, skb_tailroom(skb));
memcpy(UNIXCREDS(skb), &siocb->scm->creds, sizeof(struct ucred));
- if (siocb->scm->fp)
- unix_attach_fds(siocb->scm, skb);
+ if (siocb->scm->fp) {
+ err = unix_attach_fds(siocb->scm, skb);
+ if (err) {
+ kfree_skb(skb);
+ goto out_err;
+ }
+ }
if ((err = memcpy_fromiovec(skb_put(skb,size), msg->msg_iov, size)) != 0) {
kfree_skb(skb);

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