btrfs: fix crash on racing fsync and size-extending write into prealloc

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2024-37354
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2024-06-25 15:15:13 UTC
Updated2026-08-04 11:18:39 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: btrfs: fix crash on racing fsync and size-extending write into prealloc We have been seeing crashes on duplicate keys in btrfs_set_item_key_safe(): BTRFS critical (device vdb): slot 4 key (450 108 8192) new key (450 108 8192) ------------[ cut here ]------------ kernel BUG at fs/btrfs/ctree.c:2620! invalid opcode: 0000 [#1] PREEMPT SMP PTI CPU: 0 PID: 3139 Comm: xfs_io Kdump: loaded Not tainted 6.9.0 #6 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-2.fc40 04/01/2014 RIP: 0010:btrfs_set_item_key_safe+0x11f/0x290 [btrfs] With the following stack trace: #0 btrfs_set_item_key_safe (fs/btrfs/ctree.c:2620:4) #1 btrfs_drop_extents (fs/btrfs/file.c:411:4) #2 log_one_extent (fs/btrfs/tree-log.c:4732:9) #3 btrfs_log_changed_extents (fs/btrfs/tree-log.c:4955:9) #4 btrfs_log_inode (fs/btrfs/tree-log.c:6626:9) #5 btrfs_log_inode_parent (fs/btrfs/tree-log.c:7070:8) #6 btrfs_log_dentry_safe (fs/btrfs/tree-log.c:7171:8) #7 btrfs_sync_file (fs/btrfs/file.c:1933:8) #8 vfs_fsync_range (fs/sync.c:188:9) #9 vfs_fsync (fs/sync.c:202:9) #10 do_fsync (fs/sync.c:212:9) #11 __do_sys_fdatasync (fs/sync.c:225:9) #12 __se_sys_fdatasync (fs/sync.c:223:1) #13 __x64_sys_fdatasync (fs/sync.c:223:1) #14 do_syscall_x64 (arch/x86/entry/common.c:52:14) #15 do_syscall_64 (arch/x86/entry/common.c:83:7) #16 entry_SYSCALL_64+0xaf/0x14c (arch/x86/entry/entry_64.S:121) So we're logging a changed extent from fsync, which is splitting an extent in the log tree. But this split part already exists in the tree, triggering the BUG(). This is the state of the log tree at the time of the crash, dumped with drgn (https://github.com/osandov/drgn/blob/main/contrib/btrfs_tree.py) to get more details than btrfs_print_leaf() gives us: >>> print_extent_buffer(prog.crashed_thread().stack_trace()[0]["eb"]) leaf 33439744 level 0 items 72 generation 9 owner 18446744073709551610 leaf 33439744 flags 0x100000000000000 fs uuid e5bd3946-400c-4223-8923-190ef1f18677 chunk uuid d58cb17e-6d02-494a-829a-18b7d8a399da item 0 key (450 INODE_ITEM 0) itemoff 16123 itemsize 160 generation 7 transid 9 size 8192 nbytes 8473563889606862198 block group 0 mode 100600 links 1 uid 0 gid 0 rdev 0 sequence 204 flags 0x10(PREALLOC) atime 1716417703.220000000 (2024-05-22 15:41:43) ctime 1716417704.983333333 (2024-05-22 15:41:44) mtime 1716417704.983333333 (2024-05-22 15:41:44) otime 17592186044416.000000000 (559444-03-08 01:40:16) item 1 key (450 INODE_REF 256) itemoff 16110 itemsize 13 index 195 namelen 3 name: 193 item 2 key (450 XATTR_ITEM 1640047104) itemoff 16073 itemsize 37 location key (0 UNKNOWN.0 0) type XATTR transid 7 data_len 1 name_len 6 name: user.a data a item 3 key (450 EXTENT_DATA 0) itemoff 16020 itemsize 53 generation 9 type 1 (regular) extent data disk byte 303144960 nr 12288 extent data offset 0 nr 4096 ram 12288 extent compression 0 (none) item 4 key (450 EXTENT_DATA 4096) itemoff 15967 itemsize 53 generation 9 type 2 (prealloc) prealloc data disk byte 303144960 nr 12288 prealloc data offset 4096 nr 8192 item 5 key (450 EXTENT_DATA 8192) itemoff 15914 itemsize 53 generation 9 type 2 (prealloc) prealloc data disk byte 303144960 nr 12288 prealloc data offset 8192 nr 4096 ... So the real problem happened earlier: notice that items 4 (4k-12k) and 5 (8k-12k) overlap. Both are prealloc extents. Item 4 straddles i_size and item 5 starts at i_size. Here is the state of ---truncated---

Risk And Classification

Primary CVSS: v3.1 4.7 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

Problem Types: CWE-362

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary4.7MEDIUMCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 31d11b83b96faaee4bb514d375a09489117c3e8d c993fd02ba471e296ca1996f13626fc917120158 git Not specified
CNA Linux Linux affected 31d11b83b96faaee4bb514d375a09489117c3e8d 1ff2bd566fbcefcb892be85c493bdb92b911c428 git Not specified
CNA Linux Linux affected 31d11b83b96faaee4bb514d375a09489117c3e8d 3d08c52ba1887a1ff9c179d4b6a18b427bcb2097 git Not specified
CNA Linux Linux affected 31d11b83b96faaee4bb514d375a09489117c3e8d f4e5ed974876c14d3623e04dc43d3e3281bc6011 git Not specified
CNA Linux Linux affected 31d11b83b96faaee4bb514d375a09489117c3e8d 9d274c19a71b3a276949933859610721a453946b git Not specified
CNA Linux Linux affected 61a9f6b7fe0ca9706b49a23cecf5f9a9c802b6ce git Not specified
CNA Linux Linux affected 4.14.57 4.15 semver Not specified
CNA Linux Linux affected 4.17 Not specified
CNA Linux Linux unaffected 4.17 semver Not specified
CNA Linux Linux unaffected 5.15.197 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.94 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.34 6.6.* semver Not specified
CNA Linux Linux unaffected 6.9.5 6.9.* semver Not specified
CNA Linux Linux unaffected 6.10 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/f4e5ed974876c14d3623e04dc43d3e3281bc6011 af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Patch
git.kernel.org/stable/c/9d274c19a71b3a276949933859610721a453946b af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Patch
git.kernel.org/stable/c/c993fd02ba471e296ca1996f13626fc917120158 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/1ff2bd566fbcefcb892be85c493bdb92b911c428 af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Patch
git.kernel.org/stable/c/3d08c52ba1887a1ff9c179d4b6a18b427bcb2097 af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Patch
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