On Thu, Aug 29, 2019 at 10:51:04PM +0200, Ilya Dryomov wrote:
On Thu, Aug 29, 2019 at 8:15 PM Sasha Levin <sashal@xxxxxxxxxx> wrote:From: Luis Henriques <lhenriques@xxxxxxxx> [ Upstream commit 86968ef21596515958d5f0a40233d02be78ecec0 ] Calling ceph_buffer_put() in __ceph_setxattr() may end up freeing the i_xattrs.prealloc_blob buffer while holding the i_ceph_lock. This can be fixed by postponing the call until later, when the lock is released. The following backtrace was triggered by fstests generic/117. BUG: sleeping function called from invalid context at mm/vmalloc.c:2283 in_atomic(): 1, irqs_disabled(): 0, pid: 650, name: fsstress 3 locks held by fsstress/650: #0: 00000000870a0fe8 (sb_writers#8){.+.+}, at: mnt_want_write+0x20/0x50 #1: 00000000ba0c4c74 (&type->i_mutex_dir_key#6){++++}, at: vfs_setxattr+0x55/0xa0 #2: 000000008dfbb3f2 (&(&ci->i_ceph_lock)->rlock){+.+.}, at: __ceph_setxattr+0x297/0x810 CPU: 1 PID: 650 Comm: fsstress Not tainted 5.2.0+ #437 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58-prebuilt.qemu.org 04/01/2014 Call Trace: dump_stack+0x67/0x90 ___might_sleep.cold+0x9f/0xb1 vfree+0x4b/0x60 ceph_buffer_release+0x1b/0x60 __ceph_setxattr+0x2b4/0x810 __vfs_setxattr+0x66/0x80 __vfs_setxattr_noperm+0x59/0xf0 vfs_setxattr+0x81/0xa0 setxattr+0x115/0x230 ? filename_lookup+0xc9/0x140 ? rcu_read_lock_sched_held+0x74/0x80 ? rcu_sync_lockdep_assert+0x2e/0x60 ? __sb_start_write+0x142/0x1a0 ? mnt_want_write+0x20/0x50 path_setxattr+0xba/0xd0 __x64_sys_lsetxattr+0x24/0x30 do_syscall_64+0x50/0x1c0 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7ff23514359a Signed-off-by: Luis Henriques <lhenriques@xxxxxxxx> Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx> Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- fs/ceph/xattr.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c index 0619adbcbe14c..8382299fc2d84 100644 --- a/fs/ceph/xattr.c +++ b/fs/ceph/xattr.c @@ -1028,6 +1028,7 @@ int __ceph_setxattr(struct inode *inode, const char *name, struct ceph_inode_info *ci = ceph_inode(inode); struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc; struct ceph_cap_flush *prealloc_cf = NULL; + struct ceph_buffer *old_blob = NULL; int issued; int err; int dirty = 0; @@ -1101,13 +1102,15 @@ int __ceph_setxattr(struct inode *inode, const char *name, struct ceph_buffer *blob; spin_unlock(&ci->i_ceph_lock); - dout(" preaallocating new blob size=%d\n", required_blob_size); + ceph_buffer_put(old_blob); /* Shouldn't be required */ + dout(" pre-allocating new blob size=%d\n", required_blob_size); blob = ceph_buffer_new(required_blob_size, GFP_NOFS); if (!blob) goto do_sync_unlocked; spin_lock(&ci->i_ceph_lock); + /* prealloc_blob can't be released while holding i_ceph_lock */ if (ci->i_xattrs.prealloc_blob) - ceph_buffer_put(ci->i_xattrs.prealloc_blob); + old_blob = ci->i_xattrs.prealloc_blob; ci->i_xattrs.prealloc_blob = blob; goto retry; } @@ -1123,6 +1126,7 @@ int __ceph_setxattr(struct inode *inode, const char *name, } spin_unlock(&ci->i_ceph_lock); + ceph_buffer_put(old_blob); if (lock_snap_rwsem) up_read(&mdsc->snap_rwsem); if (dirty)Hi Sasha, I didn't tag i_ceph_lock series for stable because this is a very old bug which no one ever hit in real life, at least to my knowledge.
I can drop it if you prefer. -- Thanks, Sasha
