KASAN reports a use-after-free when running xfstest generic/531, with the
following trace:
[ 293.903362] kasan_report+0xe/0x20
[ 293.903365] rb_erase+0x1f/0x790
[ 293.903370] __ceph_remove_cap+0x201/0x370
[ 293.903375] __ceph_remove_caps+0x4b/0x70
[ 293.903380] ceph_evict_inode+0x4e/0x360
[ 293.903386] evict+0x169/0x290
[ 293.903390] __dentry_kill+0x16f/0x250
[ 293.903394] dput+0x1c6/0x440
[ 293.903398] __fput+0x184/0x330
[ 293.903404] task_work_run+0xb9/0xe0
[ 293.903410] exit_to_usermode_loop+0xd3/0xe0
[ 293.903413] do_syscall_64+0x1a0/0x1c0
[ 293.903417] entry_SYSCALL_64_after_hwframe+0x44/0xa9
This happens because __ceph_remove_cap() may queue a cap release
(__ceph_queue_cap_release) which can be scheduled before that cap is
removed from the inode list with
rb_erase(&cap->ci_node, &ci->i_caps);
And, when this finally happens, the use-after-free will occur.
This can be fixed by protecting the rb_erase with the s_cap_lock spinlock,
which is used by ceph_send_cap_releases(), before the cap is freed.
Signed-off-by: Luis Henriques <lhenriq...@suse.com>
---
fs/ceph/caps.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index d3b9c9d5c1bd..21ee38cabe98 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -1089,13 +1089,13 @@ void __ceph_remove_cap(struct ceph_cap *cap, bool
queue_release)
}
cap->cap_ino = ci->i_vino.ino;
- spin_unlock(&session->s_cap_lock);
-
/* remove from inode list */
rb_erase(&cap->ci_node, &ci->i_caps);
if (ci->i_auth_cap == cap)
ci->i_auth_cap = NULL;
+ spin_unlock(&session->s_cap_lock);
+
if (removed)
ceph_put_cap(mdsc, cap);
