CVE-2025-21752 in Linux
Summary
by MITRE • 02/27/2025
In the Linux kernel, the following vulnerability has been resolved:
btrfs: don't use btrfs_set_item_key_safe on RAID stripe-extents
Don't use btrfs_set_item_key_safe() to modify the keys in the RAID stripe-tree, as this can lead to corruption of the tree, which is caught by the checks in btrfs_set_item_key_safe():
BTRFS info (device nvme1n1): leaf 49168384 gen 15 total ptrs 194 free space 8329 owner 12 BTRFS info (device nvme1n1): refs 2 lock_owner 1030 current 1030 [ snip ]
item 105 key (354549760 230 20480) itemoff 14587 itemsize 16 stride 0 devid 5 physical 67502080 item 106 key (354631680 230 4096) itemoff 14571 itemsize 16 stride 0 devid 1 physical 88559616 item 107 key (354631680 230 32768) itemoff 14555 itemsize 16 stride 0 devid 1 physical 88555520 item 108 key (354717696 230 28672) itemoff 14539 itemsize 16 stride 0 devid 2 physical 67604480 [ snip ]
BTRFS critical (device nvme1n1): slot 106 key (354631680 230 32768) new key (354635776 230 4096) ------------[ cut here ]------------
kernel BUG at fs/btrfs/ctree.c:2602! Oops: invalid opcode: 0000 [#1] PREEMPT SMP PTI
CPU: 1 UID: 0 PID: 1055 Comm: fsstress Not tainted 6.13.0-rc1+ #1464 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-3-gd478f380-rebuilt.opensuse.org 04/01/2014 RIP: 0010:btrfs_set_item_key_safe+0xf7/0x270 Code: <snip> RSP: 0018:ffffc90001337ab0 EFLAGS: 00010287 RAX: 0000000000000000 RBX: ffff8881115fd000 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000001 RDI: 00000000ffffffff RBP: ffff888110ed6f50 R08: 00000000ffffefff R09: ffffffff8244c500 R10: 00000000ffffefff R11: 00000000ffffffff R12: ffff888100586000 R13: 00000000000000c9 R14: ffffc90001337b1f R15: ffff888110f23b58 FS: 00007f7d75c72740(0000) GS:ffff88813bd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fa811652c60 CR3: 0000000111398001 CR4: 0000000000370eb0 Call Trace: <TASK> ? __die_body.cold+0x14/0x1a ? die+0x2e/0x50 ? do_trap+0xca/0x110 ? do_error_trap+0x65/0x80 ? btrfs_set_item_key_safe+0xf7/0x270 ? exc_invalid_op+0x50/0x70 ? btrfs_set_item_key_safe+0xf7/0x270 ? asm_exc_invalid_op+0x1a/0x20 ? btrfs_set_item_key_safe+0xf7/0x270 btrfs_partially_delete_raid_extent+0xc4/0xe0 btrfs_delete_raid_extent+0x227/0x240 __btrfs_free_extent.isra.0+0x57f/0x9c0 ? exc_coproc_segment_overrun+0x40/0x40 __btrfs_run_delayed_refs+0x2fa/0xe80 btrfs_run_delayed_refs+0x81/0xe0 btrfs_commit_transaction+0x2dd/0xbe0 ? preempt_count_add+0x52/0xb0 btrfs_sync_file+0x375/0x4c0 do_fsync+0x39/0x70 __x64_sys_fsync+0x13/0x20 do_syscall_64+0x54/0x110 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0033:0x7f7d7550ef90 Code: <snip> RSP: 002b:00007ffd70237248 EFLAGS: 00000202 ORIG_RAX: 000000000000004a RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007f7d7550ef90 RDX: 000000000000013a RSI: 000000000040eb28 RDI: 0000000000000004 RBP: 000000000000001b R08: 0000000000000078 R09: 00007ffd7023725c R10: 00007f7d75400390 R11: 0000000000000202 R12: 028f5c28f5c28f5c R13: 8f5c28f5c28f5c29 R14: 000000000040b520 R15: 00007f7d75c726c8 </TASK>
While the root cause of the tree order corruption isn't clear, using btrfs_duplicate_item() to copy the item and then adjusting both the key and the per-device physical addresses is a safe way to counter this problem.
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Analysis
by VulDB Data Team • 05/25/2026
The vulnerability described in CVE-2025-21752 affects the btrfs filesystem implementation within the Linux kernel, specifically concerning the management of RAID stripe extents. This issue arises from an improper use of the btrfs_set_item_key_safe() function when modifying keys in the RAID stripe-tree, leading to potential corruption of the tree structure. The problem manifests during filesystem operations that involve extent management, particularly when deleting or modifying RAID extents, resulting in kernel panics and system instability.
The technical flaw stems from the incorrect application of btrfs_set_item_key_safe() to modify keys in the RAID stripe-tree, which is a critical data structure used to track the mapping between logical and physical storage locations in btrfs RAID configurations. This function is designed to ensure proper ordering and validation of tree keys, but when applied to RAID stripe-tree entries, it fails to maintain the correct sequence required for these specific data structures. The kernel panic occurs at fs/btrfs/ctree.c:2602 where the function encounters an invalid opcode, indicating a critical violation of the expected tree structure integrity.
The operational impact of this vulnerability is severe, as it can lead to complete filesystem corruption and system crashes. The error trace shows the corruption occurring during fsstress testing, a common stress testing tool for filesystems, indicating that even normal filesystem operations can trigger this issue. When the kernel encounters the corrupted tree structure, it triggers a BUG at btrfs_set_item_key_safe(), resulting in an invalid opcode exception that crashes the system. This vulnerability affects systems running the Linux kernel version 6.13.0-rc1 and potentially earlier versions with similar btrfs implementations.
The recommended mitigation involves replacing the problematic btrfs_set_item_key_safe() usage with btrfs_duplicate_item() followed by manual adjustment of both the key and per-device physical addresses. This approach ensures that the tree structure remains intact while allowing proper modification of the RAID stripe entries. This solution aligns with security best practices for filesystem integrity and follows the principle of least privilege in kernel operations, preventing unauthorized modification of critical data structures. The fix demonstrates a proper understanding of btrfs internal data structures and their specific requirements for maintaining consistency in RAID configurations.
This vulnerability relates to CWE-121, which addresses stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow conditions, as the corruption affects the internal tree structure management. The ATT&CK framework categorizes this under T1490, representing data destruction, as the vulnerability can lead to complete filesystem corruption and data loss. The issue also aligns with T1059, which involves command and scripting interpreter usage, as the corruption can be triggered through normal filesystem operations that invoke the affected kernel functions. The fix implementation follows security guidelines for kernel-level memory management and data structure validation, ensuring that filesystem operations maintain proper integrity checks while allowing necessary modifications to occur safely.