CVE-2022-49880: ext4: fix warning in 'ext4_da_release_space'

First published: Thu May 01 2025(Updated: )

In the Linux kernel, the following vulnerability has been resolved: ext4: fix warning in 'ext4_da_release_space' 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.

Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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