CVE-2026-93800— btrfs: fix use-after-free on reloc root after error in insert_dirty_subvol()
Quick assessment
Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
在 Linux 内核中，已修复以下漏洞： btrfs: 修复在 发生错误后对重定位根（reloc root）的使用后释放（use-after-free）问题 如果在重定位过程中，由于 返回错误，导致 执行失败，我们将使某个根（root）的 字段指向一个已被释放的重定位根，而不是设置为 NULL。这会导致后续在卸载文件系统时出现使用后释放（use-after-free）或尝试双重释放（double free）的问题。 具体步骤如下： 1) 在重定位期间， 中的 调用失败，因此 返回错误给 ，且未将该根添加到列表 中；
Possible ATT&CK Techniques 1 AI
T1499 · Endpoint Denial of ServiceAffected Version Matrix 21
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Linux | Linux | f32b84d7c977e1906a4781b93b3c93090b6cd675< 5a247097c5f94b51ffc991b444d998ad6e85875f |
affected |
592fbcd50c99b8adf999a2a54f9245caff333139< 6372dd394ea907cd85a7a8063db320ec73dfaed0 |
affected | ||
592fbcd50c99b8adf999a2a54f9245caff333139< 9f599d120b2b79d2d937c3935b7cdf2697514283 |
affected | ||
592fbcd50c99b8adf999a2a54f9245caff333139< a01837ae174a2a968c245a30e6dd010f50eaf05d |
affected | ||
592fbcd50c99b8adf999a2a54f9245caff333139< 97a540d72ebcb21853d11f2a56782fe377f358e7 |
affected | ||
592fbcd50c99b8adf999a2a54f9245caff333139< fda1b6636ff1846f00643e791099db5564b547d9 |
affected | ||
592fbcd50c99b8adf999a2a54f9245caff333139< 83201804efa4a5168be754e1dfc9b2faee760cac |
affected | ||
aa18bc1ff8a51f082d5b3b6d07693797637b4028 |
affected | ||
| … +13 more rows | |||
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I. Basic Information for CVE-2026-93800
Vulnerability Information
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Vulnerability Title
btrfs: fix use-after-free on reloc root after error in insert_dirty_subvol()
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix use-after-free on reloc root after error in insert_dirty_subvol()
If during relocation we fail in insert_dirty_subvol() because
btrfs_update_reloc_root() returned an error, we will leave a root's
reloc_root field pointing to a reloc root that was freed instead of NULL,
resulting later in a use-after-free, or double free attempt during
unmount.
The sequence of steps is this:
1) During relocation the call to btrfs_update_reloc_root() in
insert_dirty_subvol() fails, so insert_dirty_subvol() returns the
error to merge_reloc_root() without adding the root to the list
rc->dirty_subvol_roots;
2) Then merge_reloc_root() aborts the current transaction because
insert_dirty_subvol() returned an error;
3) Up the call chain, merge_reloc_roots() gets the error, adds the
reloc root for root X to the local reloc_roots list and jumps to the
'out' label, where it calls free_reloc_roots() to free all the reloc
roots in the local reloc_roots list. This frees the reloc root for
root X;
4) We go up the call chain to relocate_block_group() which calls
clean_dirty_subvols() to go over dirty roots and set their
->reloc_root field to NULL, but root X is not in the dirty_subvol_roots
list, so its ->reloc_root still points to a reloc root;
5) Relocation finishes, with an error and a transaction abort, but the
->reloc_root field for root X still points to the reloc root that was
freed in step 3;
6) When unmounting the fs we end up calling:
btrfs_free_fs_roots()
btrfs_drop_and_free_fs_root()
--> calls btrfs_put_root() against root X's ->reloc_root
which is not NULL and points to the already freed
reloc root in step 4 above
Resulting in a use-after-free to a double free attempt.
Syzbot reported this with the following dmesg/syslog:
[ 106.004389][ T5339] BTRFS error (device loop0 state A): Transaction aborted (error -5)
[ 106.014266][ T5339] BTRFS: error (device loop0 state A) in merge_reloc_root:1655: errno=-5 IO failure
[ 106.021891][ T1061] BTRFS error (device loop0 state A): error while writing out transaction: -5
[ 106.026964][ T1061] BTRFS warning (device loop0 state A): Skipping commit of aborted transaction.
[ 106.033807][ T5340] BTRFS error (device loop0 state A): bdev /dev/loop0 errs: wr 3, rd 0, flush 0, corrupt 0, gen 0
[ 106.039265][ T1061] BTRFS: error (device loop0 state A) in cleanup_transaction:2067: errno=-5 IO failure
[ 106.044382][ T5339] BTRFS info (device loop0 state EA): forced readonly
[ 106.074329][ T5339] BTRFS: error (device loop0 state EA) in merge_reloc_roots:1887: errno=-5 IO failure
[ 106.081004][ T5356] BTRFS info (device loop0 state EA): scrub: started on devid 1
[ 106.085611][ T5339] BTRFS info (device loop0 state EA): balance: ended with status: -30
[ 106.089517][ T5356] BTRFS info (device loop0 state EA): scrub: not finished on devid 1 with status: -30
[ 106.662365][ T5338] BTRFS info (device loop0 state EA): last unmount of filesystem 3a375e4e-b156-4d76-a2ad-16e198ce1409
[ 106.682946][ T5338] ==================================================================
[ 106.686574][ T5338] BUG: KASAN: slab-use-after-free in btrfs_put_root+0x2f/0x250
[ 106.690090][ T5338] Write of size 4 at addr ffff88803f978630 by task syz.0.0/5338
[ 106.693173][ T5338]
[ 106.694279][ T5338] CPU: 0 UID: 0 PID: 5338 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full)
[ 106.694293][ T5338] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[ 106.694300][ T5338] Call Trace:
[ 106.694308][ T5338] <TASK>
[ 106.694314][ T5338] dump_stack_lvl+0xe8/0x150
[ 106.694331][ T5338] print_address_description+0x55/0x1e0
[ 106.694343][ T5338] ? btrfs_put_root+0x2f/0x250
[ 106.694358][ T5338] print_report+0x58/0x70
[ 106.
---truncated---
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Affected Products
II. Public POCs for CVE-2026-93800
| # | POC Description | Source Link | Shenlong Link |
|---|
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Patches & Fixes for CVE-2026-93800 (7)
Same Patch Batch · Linux · 2026-09-24 · 234 CVEs total
| CVE-2026-93207 | 9.8 CRITICAL | SUNRPC: Zero rpc_gss_wire_cred at svcauth_gss_decode_credbody() entry |
| CVE-2026-97413 | 9.8 CRITICAL | RDMA/rtrs-srv: Fix integer underflow in process_read and process_write |
| CVE-2026-93228 | 9.1 CRITICAL | svcrdma: Reject Write/Reply chunks with segcount 0 |
| CVE-2026-93793 | 8.8 HIGH | wifi: iwlwifi: mvm: validate TX_CMD response layout |
| CVE-2026-93790 | 8.8 HIGH | wifi: iwlwifi: mvm: fix out-of-bounds tid_data access in BA notif |
| CVE-2026-93799 | 8.8 HIGH | wifi: iwlwifi: mvm: validate sta_id in BA window status notif |
| CVE-2026-97442 | 8.8 HIGH | wifi: ath11k: fix invalid data access in ath11k_dp_rx_h_undecap_nwifi |
| CVE-2026-93806 | 8.8 HIGH | wifi: cfg80211: validate assoc response length before status and IE access |
| CVE-2026-97509 | 8.8 HIGH | thunderbolt: Keep XDomain reference during the lifetime of a service |
| CVE-2026-97409 | 8.8 HIGH | nvme-fc: Do not cancel requests in io target before it is initialized |
| CVE-2026-93280 | 8.8 HIGH | greybus: audio: bound the topology section sizes against the fetched size |
| CVE-2026-93284 | 8.8 HIGH | drm/pagemap: dma-unmap pages before handling migration errors |
| CVE-2026-97451 | 8.4 HIGH | ACPICA: Fix integer overflow in acpi_ex_opcode_3A_1T_1R() (mid_op) |
| CVE-2026-97452 | 8.4 HIGH | ACPICA: Prevent adding invalid references |
| CVE-2026-97455 | 8.4 HIGH | ACPICA: Fix use-after-free in acpi_ds_terminate_control_method() |
| CVE-2026-97450 | 8.4 HIGH | ACPICA: validate handler object type in two places |
| CVE-2026-93827 | 8.4 HIGH | virtio-fs: avoid double-free on failed queue setup |
| CVE-2026-97433 | 8.2 HIGH | nvme: validate FDP configuration descriptor sizes |
| CVE-2026-93224 | 8.1 HIGH | svcrdma: Fix unmatched rn_unregister on failed accept |
| CVE-2026-93787 | 8.1 HIGH | smb: client: bound dirent name against end of SMB response in cifs_filldir |
Showing top 20 of 234 CVEs. View all on vendor page → →
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Same vendor: Linux
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CVE-2026-98384
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V. Comments for CVE-2026-93800
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