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| author | Stefano Stabellini <sstabellini@kernel.org> | 2017-11-15 13:20:21 -0800 |
|---|---|---|
| committer | Boris Ostrovsky <boris.ostrovsky@oracle.com> | 2017-11-15 16:38:15 -0500 |
| commit | 646d944c2ef5a3b298c4e150494c71b9272d8b47 (patch) | |
| tree | 7dc5ca8c8681c80b438db0babfebe26e2f1ecbc0 /drivers | |
| parent | 24e7f84db0db6b6f14581707a45d06ec5d5b88f2 (diff) | |
| download | linux-646d944c2ef5a3b298c4e150494c71b9272d8b47.tar.bz2 | |
xen/pvcalls: fix potential endless loop in pvcalls-front.c
mutex_trylock() returns 1 if you take the lock and 0 if not. Assume you
take in_mutex on the first try, but you can't take out_mutex. Next times
you call mutex_trylock() in_mutex is going to fail. It's an endless
loop.
Solve the problem by waiting until the global refcount is 1 instead (the
refcount is 1 when the only active pvcalls frontend function is
pvcalls_front_release).
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/xen/pvcalls-front.c | 11 |
1 files changed, 5 insertions, 6 deletions
diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c index 9e40c2cd70b1..40caa92bff33 100644 --- a/drivers/xen/pvcalls-front.c +++ b/drivers/xen/pvcalls-front.c @@ -1041,13 +1041,12 @@ int pvcalls_front_release(struct socket *sock) wake_up_interruptible(&map->active.inflight_conn_req); /* - * Wait until there are no more waiters on the mutexes. - * We know that no new waiters can be added because sk_send_head - * is set to NULL -- we only need to wait for the existing - * waiters to return. + * We need to make sure that sendmsg/recvmsg on this socket have + * not started before we've cleared sk_send_head here. The + * easiest (though not optimal) way to guarantee this is to see + * that no pvcall (other than us) is in progress. */ - while (!mutex_trylock(&map->active.in_mutex) || - !mutex_trylock(&map->active.out_mutex)) + while (atomic_read(&pvcalls_refcount) > 1) cpu_relax(); pvcalls_front_free_map(bedata, map); |