CVE-2023-53187
Unknown
Unknown - Not Provided
BaseFortify
Publication date: 2025-09-15
Last updated on: 2025-12-02
Assigner: kernel.org
Description
Description
In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix use-after-free of new block group that became unused
If a task creates a new block group and that block group becomes unused
before we finish its creation, at btrfs_create_pending_block_groups(),
then when btrfs_mark_bg_unused() is called against the block group, we
assume that the block group is currently in the list of block groups to
reclaim, and we move it out of the list of new block groups and into the
list of unused block groups. This has two consequences:
1) We move it out of the list of new block groups associated to the
current transaction. So the block group creation is not finished and
if we attempt to delete the bg because it's unused, we will not find
the block group item in the extent tree (or the new block group tree),
its device extent items in the device tree etc, resulting in the
deletion to fail due to the missing items;
2) We don't increment the reference count on the block group when we
move it to the list of unused block groups, because we assumed the
block group was on the list of block groups to reclaim, and in that
case it already has the correct reference count. However the block
group was on the list of new block groups, in which case no extra
reference was taken because it's local to the current task. This
later results in doing an extra reference count decrement when
removing the block group from the unused list, eventually leading the
reference count to 0.
This second case was caught when running generic/297 from fstests, which
produced the following assertion failure and stack trace:
[589.559] assertion failed: refcount_read(&block_group->refs) == 1, in fs/btrfs/block-group.c:4299
[589.559] ------------[ cut here ]------------
[589.559] kernel BUG at fs/btrfs/block-group.c:4299!
[589.560] invalid opcode: 0000 [#1] PREEMPT SMP PTI
[589.560] CPU: 8 PID: 2819134 Comm: umount Tainted: G W 6.4.0-rc6-btrfs-next-134+ #1
[589.560] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014
[589.560] RIP: 0010:btrfs_free_block_groups+0x449/0x4a0 [btrfs]
[589.561] Code: 68 62 da c0 (...)
[589.561] RSP: 0018:ffffa55a8c3b3d98 EFLAGS: 00010246
[589.561] RAX: 0000000000000058 RBX: ffff8f030d7f2000 RCX: 0000000000000000
[589.562] RDX: 0000000000000000 RSI: ffffffff953f0878 RDI: 00000000ffffffff
[589.562] RBP: ffff8f030d7f2088 R08: 0000000000000000 R09: ffffa55a8c3b3c50
[589.562] R10: 0000000000000001 R11: 0000000000000001 R12: ffff8f05850b4c00
[589.562] R13: ffff8f030d7f2090 R14: ffff8f05850b4cd8 R15: dead000000000100
[589.563] FS: 00007f497fd2e840(0000) GS:ffff8f09dfc00000(0000) knlGS:0000000000000000
[589.563] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[589.563] CR2: 00007f497ff8ec10 CR3: 0000000271472006 CR4: 0000000000370ee0
[589.563] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[589.564] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[589.564] Call Trace:
[589.564] <TASK>
[589.565] ? __die_body+0x1b/0x60
[589.565] ? die+0x39/0x60
[589.565] ? do_trap+0xeb/0x110
[589.565] ? btrfs_free_block_groups+0x449/0x4a0 [btrfs]
[589.566] ? do_error_trap+0x6a/0x90
[589.566] ? btrfs_free_block_groups+0x449/0x4a0 [btrfs]
[589.566] ? exc_invalid_op+0x4e/0x70
[589.566] ? btrfs_free_block_groups+0x449/0x4a0 [btrfs]
[589.567] ? asm_exc_invalid_op+0x16/0x20
[589.567] ? btrfs_free_block_groups+0x449/0x4a0 [btrfs]
[589.567] ? btrfs_free_block_groups+0x449/0x4a0 [btrfs]
[589.567] close_ctree+0x35d/0x560 [btrfs]
[589.568] ? fsnotify_sb_delete+0x13e/0x1d0
[589.568] ? dispose_list+0x3a/0x50
[589.568] ? evict_inodes+0x151/0x1a0
[589.568] generic_shutdown_super+0x73/0x1a0
[589.569] kill_anon_super+0x14/0x30
[589.569] btrfs_kill_super+0x12/0x20 [btrfs]
[589.569] deactivate_locked
---truncated---
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| linux | linux_kernel | From 5.15.128 (inc) to 5.16 (exc) |
| linux | linux_kernel | 6.5 |
| linux | linux_kernel | 6.5 |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-416 | The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability is a use-after-free bug in the Linux kernel's btrfs filesystem. It occurs when a new block group is created but becomes unused before its creation finishes. The kernel incorrectly moves this block group from the 'new block groups' list to the 'unused block groups' list without properly updating reference counts. This leads to an extra decrement of the reference count, eventually causing the reference count to reach zero prematurely, which can trigger a kernel crash or bug due to accessing freed memory.
How can this vulnerability impact me? :
This vulnerability can cause a kernel crash or system instability due to a use-after-free condition in the btrfs filesystem. If exploited or triggered, it may lead to data loss, system downtime, or denial of service as the kernel encounters a fatal error when handling block groups in btrfs.
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