xen/gntdev: Fix sleep-inside-spinlock
BUG: sleeping function called from invalid context at /local/scratch/dariof/linux/kernel/mutex.c:271
in_atomic(): 1, irqs_disabled(): 0, pid: 3256, name: qemu-dm
1 lock held by qemu-dm/3256:
#0: (&(&priv->lock)->rlock){......}, at: [<ffffffff813223da>] gntdev_ioctl+0x2bd/0x4d5
Pid: 3256, comm: qemu-dm Tainted: G W 3.1.0-rc8+ #5
Call Trace:
[<ffffffff81054594>] __might_sleep+0x131/0x135
[<ffffffff816bd64f>] mutex_lock_nested+0x25/0x45
[<ffffffff8131c7c8>] free_xenballooned_pages+0x20/0xb1
[<ffffffff8132194d>] gntdev_put_map+0xa8/0xdb
[<ffffffff816be546>] ? _raw_spin_lock+0x71/0x7a
[<ffffffff813223da>] ? gntdev_ioctl+0x2bd/0x4d5
[<ffffffff8132243c>] gntdev_ioctl+0x31f/0x4d5
[<ffffffff81007d62>] ? check_events+0x12/0x20
[<ffffffff811433bc>] do_vfs_ioctl+0x488/0x4d7
[<ffffffff81007d4f>] ? xen_restore_fl_direct_reloc+0x4/0x4
[<ffffffff8109168b>] ? lock_release+0x21c/0x229
[<ffffffff81135cdd>] ? rcu_read_unlock+0x21/0x32
[<ffffffff81143452>] sys_ioctl+0x47/0x6a
[<ffffffff816bfd82>] system_call_fastpath+0x16/0x1b
gntdev_put_map tries to acquire a mutex when freeing pages back to the
xenballoon pool, so it cannot be called with a spinlock held. In
gntdev_release, the spinlock is not needed as we are freeing the
structure later; in the ioctl, only the list manipulation needs to be
under the lock.
Reported-and-Tested-By: Dario Faggioli <dario.faggioli@citrix.com>
Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 3e3603f..880798a 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -492,13 +492,11 @@
pr_debug("priv %p\n", priv);
- spin_lock(&priv->lock);
while (!list_empty(&priv->maps)) {
map = list_entry(priv->maps.next, struct grant_map, next);
list_del(&map->next);
gntdev_put_map(map);
}
- spin_unlock(&priv->lock);
if (use_ptemod)
mmu_notifier_unregister(&priv->mn, priv->mm);
@@ -562,10 +560,11 @@
map = gntdev_find_map_index(priv, op.index >> PAGE_SHIFT, op.count);
if (map) {
list_del(&map->next);
- gntdev_put_map(map);
err = 0;
}
spin_unlock(&priv->lock);
+ if (map)
+ gntdev_put_map(map);
return err;
}