Messages in this thread | | | Date | Thu, 29 Aug 2019 17:16:40 -0400 | From | Sasha Levin <> | Subject | Re: [PATCH AUTOSEL 5.2 66/76] ceph: fix buffer free while holding i_ceph_lock in __ceph_setxattr() |
| |
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@kernel.org> wrote: >> >> From: Luis Henriques <lhenriques@suse.com> >> >> [ 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@suse.com> >> Reviewed-by: Jeff Layton <jlayton@kernel.org> >> Signed-off-by: Ilya Dryomov <idryomov@gmail.com> >> Signed-off-by: Sasha Levin <sashal@kernel.org> >> --- >> 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
| |