Re: [PATCH -next v2] ext4: fix warning in 'ext4_da_release_space'

From: Jan Kara
Date: Tue Oct 18 2022 - 09:58:15 EST


On Tue 18-10-22 10:27:01, Ye Bin wrote:
> Syzkaller report issue as follows:
> EXT4-fs (loop0): Free/Dirty block details
> EXT4-fs (loop0): free_blocks=0
> EXT4-fs (loop0): dirty_blocks=0
> EXT4-fs (loop0): Block reservation details
> EXT4-fs (loop0): i_reserved_data_blocks=0
> EXT4-fs warning (device loop0): ext4_da_release_space:1527: ext4_da_release_space: ino 18, to_free 1 with only 0 reserved data blocks
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 92 at fs/ext4/inode.c:1528 ext4_da_release_space+0x25e/0x370 fs/ext4/inode.c:1524
> Modules linked in:
> CPU: 0 PID: 92 Comm: kworker/u4:4 Not tainted 6.0.0-syzkaller-09423-g493ffd6605b2 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
> Workqueue: writeback wb_workfn (flush-7:0)
> RIP: 0010:ext4_da_release_space+0x25e/0x370 fs/ext4/inode.c:1528
> RSP: 0018:ffffc900015f6c90 EFLAGS: 00010296
> RAX: 42215896cd52ea00 RBX: 0000000000000000 RCX: 42215896cd52ea00
> RDX: 0000000000000000 RSI: 0000000080000001 RDI: 0000000000000000
> RBP: 1ffff1100e907d96 R08: ffffffff816aa79d R09: fffff520002bece5
> R10: fffff520002bece5 R11: 1ffff920002bece4 R12: ffff888021fd2000
> R13: ffff88807483ecb0 R14: 0000000000000001 R15: ffff88807483e740
> FS: 0000000000000000(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00005555569ba628 CR3: 000000000c88e000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> ext4_es_remove_extent+0x1ab/0x260 fs/ext4/extents_status.c:1461
> mpage_release_unused_pages+0x24d/0xef0 fs/ext4/inode.c:1589
> ext4_writepages+0x12eb/0x3be0 fs/ext4/inode.c:2852
> do_writepages+0x3c3/0x680 mm/page-writeback.c:2469
> __writeback_single_inode+0xd1/0x670 fs/fs-writeback.c:1587
> writeback_sb_inodes+0xb3b/0x18f0 fs/fs-writeback.c:1870
> wb_writeback+0x41f/0x7b0 fs/fs-writeback.c:2044
> wb_do_writeback fs/fs-writeback.c:2187 [inline]
> wb_workfn+0x3cb/0xef0 fs/fs-writeback.c:2227
> process_one_work+0x877/0xdb0 kernel/workqueue.c:2289
> worker_thread+0xb14/0x1330 kernel/workqueue.c:2436
> kthread+0x266/0x300 kernel/kthread.c:376
> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
> </TASK>
>
> Above issue may happens as follows:
> ext4_da_write_begin
> ext4_create_inline_data
> ext4_clear_inode_flag(inode, EXT4_INODE_EXTENTS);
> ext4_set_inode_flag(inode, EXT4_INODE_INLINE_DATA);
> __ext4_ioctl
> ext4_ext_migrate -> will lead to eh->eh_entries not zero, and set extent flag
> ext4_da_write_begin
> ext4_da_convert_inline_data_to_extent
> ext4_da_write_inline_data_begin
> ext4_da_map_blocks
> ext4_insert_delayed_block
> if (!ext4_es_scan_clu(inode, &ext4_es_is_delonly, lblk))
> if (!ext4_es_scan_clu(inode, &ext4_es_is_mapped, lblk))
> ext4_clu_mapped(inode, EXT4_B2C(sbi, lblk)); -> will return 1
> allocated = true;
> ext4_es_insert_delayed_block(inode, lblk, allocated);
> ext4_writepages
> mpage_map_and_submit_extent(handle, &mpd, &give_up_on_write); -> return -ENOSPC
> mpage_release_unused_pages(&mpd, give_up_on_write); -> give_up_on_write == 1
> ext4_es_remove_extent
> ext4_da_release_space(inode, reserved);
> if (unlikely(to_free > ei->i_reserved_data_blocks))
> -> to_free == 1 but ei->i_reserved_data_blocks == 0
> -> then trigger warning as above
>
> To solve above issue, forbid inode do migrate which has inline data.
>
> Reported-by: syzbot+c740bb18df70ad00952e@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Ye Bin <yebin10@xxxxxxxxxx>

Yeah, makes sense. Feel free to add:

Reviewed-by: Jan Kara <jack@xxxxxxx>

Honza

> ---
> fs/ext4/migrate.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
> index 0a220ec9862d..a19a9661646e 100644
> --- a/fs/ext4/migrate.c
> +++ b/fs/ext4/migrate.c
> @@ -424,7 +424,8 @@ int ext4_ext_migrate(struct inode *inode)
> * already is extent-based, error out.
> */
> if (!ext4_has_feature_extents(inode->i_sb) ||
> - (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
> + ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS) ||
> + ext4_has_inline_data(inode))
> return -EINVAL;
>
> if (S_ISLNK(inode->i_mode) && inode->i_blocks == 0)
> --
> 2.31.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR