From 58af68f4f16de69243dea8ee501da43dd22d6d65 Mon Sep 17 00:00:00 2001 From: Luis Henriques Date: Fri, 25 Oct 2019 14:05:24 +0100 Subject: ceph: fix use-after-free in __ceph_remove_cap() commit ea60ed6fcf29eebc78f2ce91491e6309ee005a01 upstream. 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 removing the cap from the inode list before being removed from the session list, and thus eliminating the risk of an UAF. Cc: stable@vger.kernel.org Signed-off-by: Luis Henriques Reviewed-by: Jeff Layton Signed-off-by: Ilya Dryomov Signed-off-by: Greg Kroah-Hartman --- fs/ceph/caps.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c index df95e39ccd45..c3a3ee74e2d8 100644 --- a/fs/ceph/caps.c +++ b/fs/ceph/caps.c @@ -935,6 +935,11 @@ void __ceph_remove_cap(struct ceph_cap *cap, bool queue_release) dout("__ceph_remove_cap %p from %p\n", cap, &ci->vfs_inode); + /* remove from inode's cap rbtree, and clear auth cap */ + rb_erase(&cap->ci_node, &ci->i_caps); + if (ci->i_auth_cap == cap) + ci->i_auth_cap = NULL; + /* remove from session list */ spin_lock(&session->s_cap_lock); if (session->s_cap_iterator == cap) { @@ -970,11 +975,6 @@ void __ceph_remove_cap(struct ceph_cap *cap, bool queue_release) 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; - if (removed) ceph_put_cap(mdsc, cap); -- cgit v1.2.3