On 2020/7/26 下午8:41, gregkh@xxxxxxxxxxxxxxxxxxx wrote: > > This is a note to let you know that I've just added the patch titled > > btrfs: qgroup: fix data leak caused by race between writeback and truncate > > to the 4.14-stable tree which can be found at: > http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary > > The filename of the patch is: > btrfs-qgroup-fix-data-leak-caused-by-race-between-writeback-and-truncate.patch > and it can be found in the queue-4.14 subdirectory. > > If you, or anyone else, feels it should not be added to the stable tree, > please let <stable@xxxxxxxxxxxxxxx> know about it. Please don't merge this patch for any of the stable branches. This patch needs one unmerged patch ("btrfs: change timing for qgroup reserved space for ordered extents to fix reserved space leak", already in maintainer's tree) as prerequisite. The behavior without that patch could be problematic. I should have noticed this earlier. Thanks, Qu > > > From fa91e4aa1716004ea8096d5185ec0451e206aea0 Mon Sep 17 00:00:00 2001 > From: Qu Wenruo <wqu@xxxxxxxx> > Date: Fri, 17 Jul 2020 15:12:05 +0800 > Subject: btrfs: qgroup: fix data leak caused by race between writeback and truncate > > From: Qu Wenruo <wqu@xxxxxxxx> > > commit fa91e4aa1716004ea8096d5185ec0451e206aea0 upstream. > > [BUG] > When running tests like generic/013 on test device with btrfs quota > enabled, it can normally lead to data leak, detected at unmount time: > > BTRFS warning (device dm-3): qgroup 0/5 has unreleased space, type 0 rsv 4096 > ------------[ cut here ]------------ > WARNING: CPU: 11 PID: 16386 at fs/btrfs/disk-io.c:4142 close_ctree+0x1dc/0x323 [btrfs] > RIP: 0010:close_ctree+0x1dc/0x323 [btrfs] > Call Trace: > btrfs_put_super+0x15/0x17 [btrfs] > generic_shutdown_super+0x72/0x110 > kill_anon_super+0x18/0x30 > btrfs_kill_super+0x17/0x30 [btrfs] > deactivate_locked_super+0x3b/0xa0 > deactivate_super+0x40/0x50 > cleanup_mnt+0x135/0x190 > __cleanup_mnt+0x12/0x20 > task_work_run+0x64/0xb0 > __prepare_exit_to_usermode+0x1bc/0x1c0 > __syscall_return_slowpath+0x47/0x230 > do_syscall_64+0x64/0xb0 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > ---[ end trace caf08beafeca2392 ]--- > BTRFS error (device dm-3): qgroup reserved space leaked > > [CAUSE] > In the offending case, the offending operations are: > 2/6: writev f2X[269 1 0 0 0 0] [1006997,67,288] 0 > 2/7: truncate f2X[269 1 0 0 48 1026293] 18388 0 > > The following sequence of events could happen after the writev(): > CPU1 (writeback) | CPU2 (truncate) > ----------------------------------------------------------------- > btrfs_writepages() | > |- extent_write_cache_pages() | > |- Got page for 1003520 | > | 1003520 is Dirty, no writeback | > | So (!clear_page_dirty_for_io()) | > | gets called for it | > |- Now page 1003520 is Clean. | > | | btrfs_setattr() > | | |- btrfs_setsize() > | | |- truncate_setsize() > | | New i_size is 18388 > |- __extent_writepage() | > | |- page_offset() > i_size | > |- btrfs_invalidatepage() | > |- Page is clean, so no qgroup | > callback executed > > This means, the qgroup reserved data space is not properly released in > btrfs_invalidatepage() as the page is Clean. > > [FIX] > Instead of checking the dirty bit of a page, call > btrfs_qgroup_free_data() unconditionally in btrfs_invalidatepage(). > > As qgroup rsv are completely bound to the QGROUP_RESERVED bit of > io_tree, not bound to page status, thus we won't cause double freeing > anyway. > > Fixes: 0b34c261e235 ("btrfs: qgroup: Prevent qgroup->reserved from going subzero") > CC: stable@xxxxxxxxxxxxxxx # 4.14+ > Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx> > Signed-off-by: Qu Wenruo <wqu@xxxxxxxx> > Signed-off-by: David Sterba <dsterba@xxxxxxxx> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > > --- > fs/btrfs/inode.c | 23 ++++++++++------------- > 1 file changed, 10 insertions(+), 13 deletions(-) > > --- a/fs/btrfs/inode.c > +++ b/fs/btrfs/inode.c > @@ -9197,20 +9197,17 @@ again: > /* > * Qgroup reserved space handler > * Page here will be either > - * 1) Already written to disk > - * In this case, its reserved space is released from data rsv map > - * and will be freed by delayed_ref handler finally. > - * So even we call qgroup_free_data(), it won't decrease reserved > - * space. > - * 2) Not written to disk > - * This means the reserved space should be freed here. However, > - * if a truncate invalidates the page (by clearing PageDirty) > - * and the page is accounted for while allocating extent > - * in btrfs_check_data_free_space() we let delayed_ref to > - * free the entire extent. > + * 1) Already written to disk or ordered extent already submitted > + * Then its QGROUP_RESERVED bit in io_tree is already cleaned. > + * Qgroup will be handled by its qgroup_record then. > + * btrfs_qgroup_free_data() call will do nothing here. > + * > + * 2) Not written to disk yet > + * Then btrfs_qgroup_free_data() call will clear the QGROUP_RESERVED > + * bit of its io_tree, and free the qgroup reserved data space. > + * Since the IO will never happen for this page. > */ > - if (PageDirty(page)) > - btrfs_qgroup_free_data(inode, NULL, page_start, PAGE_SIZE); > + btrfs_qgroup_free_data(inode, NULL, page_start, PAGE_SIZE); > if (!inode_evicting) { > clear_extent_bit(tree, page_start, page_end, > EXTENT_LOCKED | EXTENT_DIRTY | > > > Patches currently in stable-queue which might be from wqu@xxxxxxxx are > > queue-4.14/btrfs-qgroup-fix-data-leak-caused-by-race-between-writeback-and-truncate.patch >
