ext4: fix slab-use-after-free in ext4_split_extent_at()

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Summary

CVECVE-2024-49884
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2024-10-21 18:15:11 UTC
Updated2026-05-12 19:09:03 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: ext4: fix slab-use-after-free in ext4_split_extent_at() We hit the following use-after-free: ================================================================== BUG: KASAN: slab-use-after-free in ext4_split_extent_at+0xba8/0xcc0 Read of size 2 at addr ffff88810548ed08 by task kworker/u20:0/40 CPU: 0 PID: 40 Comm: kworker/u20:0 Not tainted 6.9.0-dirty #724 Call Trace: <TASK> kasan_report+0x93/0xc0 ext4_split_extent_at+0xba8/0xcc0 ext4_split_extent.isra.0+0x18f/0x500 ext4_split_convert_extents+0x275/0x750 ext4_ext_handle_unwritten_extents+0x73e/0x1580 ext4_ext_map_blocks+0xe20/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] Allocated by task 40: __kmalloc_noprof+0x1ac/0x480 ext4_find_extent+0xf3b/0x1e70 ext4_ext_map_blocks+0x188/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] Freed by task 40: kfree+0xf1/0x2b0 ext4_find_extent+0xa71/0x1e70 ext4_ext_insert_extent+0xa22/0x3260 ext4_split_extent_at+0x3ef/0xcc0 ext4_split_extent.isra.0+0x18f/0x500 ext4_split_convert_extents+0x275/0x750 ext4_ext_handle_unwritten_extents+0x73e/0x1580 ext4_ext_map_blocks+0xe20/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] ================================================================== The flow of issue triggering is as follows: ext4_split_extent_at path = *ppath ext4_ext_insert_extent(ppath) ext4_ext_create_new_leaf(ppath) ext4_find_extent(orig_path) path = *orig_path read_extent_tree_block // return -ENOMEM or -EIO ext4_free_ext_path(path) kfree(path) *orig_path = NULL a. If err is -ENOMEM: ext4_ext_dirty(path + path->p_depth) // path use-after-free !!! b. If err is -EIO and we have EXT_DEBUG defined: ext4_ext_show_leaf(path) eh = path[depth].p_hdr // path also use-after-free !!! So when trying to zeroout or fix the extent length, call ext4_find_extent() to update the path. In addition we use *ppath directly as an ext4_ext_show_leaf() input to avoid possible use-after-free when EXT_DEBUG is defined, and to avoid unnecessary path updates.

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from [email protected]

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

Problem Types: CWE-416

CVSS v3.1 Breakdown

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

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Debian Debian Linux 11.0 All All All
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected dfe5080939ea4686b3414b5d970a9b26733c57a4 393a46f60ea4f249dc9d496d4eb2d542f5e11ade git Not specified
CNA Linux Linux affected dfe5080939ea4686b3414b5d970a9b26733c57a4 448100a29395b0c8b4c42967155849fe0fbe808f git Not specified
CNA Linux Linux affected dfe5080939ea4686b3414b5d970a9b26733c57a4 e52f933598b781d291b9297e39c463536da0e185 git Not specified
CNA Linux Linux affected dfe5080939ea4686b3414b5d970a9b26733c57a4 cafcc1bd62934547c76abf46c6d0d54f135006fe git Not specified
CNA Linux Linux affected dfe5080939ea4686b3414b5d970a9b26733c57a4 a5401d4c3e2a3d25643c567d26e6de327774a2c9 git Not specified
CNA Linux Linux affected dfe5080939ea4686b3414b5d970a9b26733c57a4 8fe117790b37c84c651e2bad9efc0e7fda73c0e3 git Not specified
CNA Linux Linux affected dfe5080939ea4686b3414b5d970a9b26733c57a4 5d949ea75bb529ea6342e83465938a3b0ac51238 git Not specified
CNA Linux Linux affected dfe5080939ea4686b3414b5d970a9b26733c57a4 915ac3630488af0ca194dc63b86d99802b4f6e18 git Not specified
CNA Linux Linux affected dfe5080939ea4686b3414b5d970a9b26733c57a4 c26ab35702f8cd0cdc78f96aa5856bfb77be798f git Not specified
CNA Linux Linux affected 3.18 Not specified
CNA Linux Linux unaffected 3.18 semver Not specified
CNA Linux Linux unaffected 4.19.323 4.19.* semver Not specified
CNA Linux Linux unaffected 5.4.290 5.4.* semver Not specified
CNA Linux Linux unaffected 5.10.227 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.168 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.113 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.55 6.6.* semver Not specified
CNA Linux Linux unaffected 6.10.14 6.10.* semver Not specified
CNA Linux Linux unaffected 6.11.3 6.11.* semver Not specified
CNA Linux Linux unaffected 6.12 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/8fe117790b37c84c651e2bad9efc0e7fda73c0e3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
lists.debian.org/debian-lts-announce/2025/03/msg00002.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org Mailing List, Third Party Advisory
git.kernel.org/stable/c/393a46f60ea4f249dc9d496d4eb2d542f5e11ade 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/c26ab35702f8cd0cdc78f96aa5856bfb77be798f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/448100a29395b0c8b4c42967155849fe0fbe808f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/cafcc1bd62934547c76abf46c6d0d54f135006fe 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/5d949ea75bb529ea6342e83465938a3b0ac51238 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/915ac3630488af0ca194dc63b86d99802b4f6e18 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
lists.debian.org/debian-lts-announce/2025/01/msg00001.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org Broken Link
git.kernel.org/stable/c/e52f933598b781d291b9297e39c463536da0e185 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/a5401d4c3e2a3d25643c567d26e6de327774a2c9 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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