ext4: check dot and dotdot of dx_root before making dir indexed

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2024-42305
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2024-08-17 09:15:10 UTC
Updated2026-05-12 12:17:06 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: ext4: check dot and dotdot of dx_root before making dir indexed Syzbot reports a issue as follows: ============================================ BUG: unable to handle page fault for address: ffffed11022e24fe PGD 23ffee067 P4D 23ffee067 PUD 0 Oops: Oops: 0000 [#1] PREEMPT SMP KASAN PTI CPU: 0 PID: 5079 Comm: syz-executor306 Not tainted 6.10.0-rc5-g55027e689933 #0 Call Trace: <TASK> make_indexed_dir+0xdaf/0x13c0 fs/ext4/namei.c:2341 ext4_add_entry+0x222a/0x25d0 fs/ext4/namei.c:2451 ext4_rename fs/ext4/namei.c:3936 [inline] ext4_rename2+0x26e5/0x4370 fs/ext4/namei.c:4214 [...] ============================================ The immediate cause of this problem is that there is only one valid dentry for the block to be split during do_split, so split==0 results in out of bounds accesses to the map triggering the issue. do_split unsigned split dx_make_map count = 1 split = count/2 = 0; continued = hash2 == map[split - 1].hash; ---> map[4294967295] The maximum length of a filename is 255 and the minimum block size is 1024, so it is always guaranteed that the number of entries is greater than or equal to 2 when do_split() is called. But syzbot's crafted image has no dot and dotdot in dir, and the dentry distribution in dirblock is as follows: bus dentry1 hole dentry2 free |xx--|xx-------------|...............|xx-------------|...............| 0 12 (8+248)=256 268 256 524 (8+256)=264 788 236 1024 So when renaming dentry1 increases its name_len length by 1, neither hole nor free is sufficient to hold the new dentry, and make_indexed_dir() is called. In make_indexed_dir() it is assumed that the first two entries of the dirblock must be dot and dotdot, so bus and dentry1 are left in dx_root because they are treated as dot and dotdot, and only dentry2 is moved to the new leaf block. That's why count is equal to 1. Therefore add the ext4_check_dx_root() helper function to add more sanity checks to dot and dotdot before starting the conversion to avoid the above issue.

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

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

Problem Types: CWE-125

CVSS v3.1 Breakdown

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

CVSS:3.1/AV:L/AC:L/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 ac27a0ec112a089f1a5102bc8dffc79c8c815571 b80575ffa98b5bb3a5d4d392bfe4c2e03e9557db git Not specified
CNA Linux Linux affected ac27a0ec112a089f1a5102bc8dffc79c8c815571 19e13b4d7f0303186fcc891aba8d0de7c8fdbda8 git Not specified
CNA Linux Linux affected ac27a0ec112a089f1a5102bc8dffc79c8c815571 42d420517072028fb0eb852c358056b7717ba5aa git Not specified
CNA Linux Linux affected ac27a0ec112a089f1a5102bc8dffc79c8c815571 8afe06ed3be7a874b3cd82ef5f8959aca8d6429a git Not specified
CNA Linux Linux affected ac27a0ec112a089f1a5102bc8dffc79c8c815571 abb411ac991810c0bcbe51c2e76d2502bf611b5c git Not specified
CNA Linux Linux affected ac27a0ec112a089f1a5102bc8dffc79c8c815571 9d241b7a39af192d1bb422714a458982c7cc67a2 git Not specified
CNA Linux Linux affected ac27a0ec112a089f1a5102bc8dffc79c8c815571 cdd345321699042ece4a9d2e70754d2397d378c5 git Not specified
CNA Linux Linux affected ac27a0ec112a089f1a5102bc8dffc79c8c815571 50ea741def587a64e08879ce6c6a30131f7111e7 git Not specified
CNA Linux Linux affected 2.6.19 Not specified
CNA Linux Linux unaffected 2.6.19 semver Not specified
CNA Linux Linux unaffected 4.19.320 4.19.* semver Not specified
CNA Linux Linux unaffected 5.4.282 5.4.* semver Not specified
CNA Linux Linux unaffected 5.10.224 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.165 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.103 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.44 6.6.* semver Not specified
CNA Linux Linux unaffected 6.10.3 6.10.* semver Not specified
CNA Linux Linux unaffected 6.11 * original_commit_for_fix Not specified
ADP Siemens SIMATIC S7-1500 TM MFP - GNU/Linux Subsystem affected * custom Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/19e13b4d7f0303186fcc891aba8d0de7c8fdbda8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/9d241b7a39af192d1bb422714a458982c7cc67a2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/b80575ffa98b5bb3a5d4d392bfe4c2e03e9557db 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/42d420517072028fb0eb852c358056b7717ba5aa 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/cdd345321699042ece4a9d2e70754d2397d378c5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
cert-portal.siemens.com/productcert/html/ssa-265688.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
git.kernel.org/stable/c/50ea741def587a64e08879ce6c6a30131f7111e7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
lists.debian.org/debian-lts-announce/2024/10/msg00003.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org
lists.debian.org/debian-lts-announce/2025/01/msg00001.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org
git.kernel.org/stable/c/abb411ac991810c0bcbe51c2e76d2502bf611b5c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/8afe06ed3be7a874b3cd82ef5f8959aca8d6429a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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