Description

In the Linux kernel, the following vulnerability has been resolved: ext4: fix slab-out-of-bounds in ext4_mb_find_good_group_avg_frag_lists() We can trigger a slab-out-of-bounds with the following commands: mkfs.ext4 -F /dev/$disk 10G mount /dev/$disk /tmp/test echo 2147483647 > /sys/fs/ext4/$disk/mb_group_prealloc echo test > /tmp/test/file && sync ================================================================== BUG: KASAN: slab-out-of-bounds in ext4_mb_find_good_group_avg_frag_lists+0x8a/0x200 [ext4] Read of size 8 at addr ffff888121b9d0f0 by task kworker/u2:0/11 CPU: 0 PID: 11 Comm: kworker/u2:0 Tainted: GL 6.7.0-next-20240118 #521 Call Trace: dump_stack_lvl+0x2c/0x50 kasan_report+0xb6/0xf0 ext4_mb_find_good_group_avg_frag_lists+0x8a/0x200 [ext4] ext4_mb_regular_allocator+0x19e9/0x2370 [ext4] ext4_mb_new_blocks+0x88a/0x1370 [ext4] ext4_ext_map_blocks+0x14f7/0x2390 [ext4] ext4_map_blocks+0x569/0xea0 [ext4] ext4_do_writepages+0x10f6/0x1bc0 [ext4] [...] ================================================================== The flow of issue triggering is as follows: // Set s_mb_group_prealloc to 2147483647 via sysfs ext4_mb_new_blocks ext4_mb_normalize_request ext4_mb_normalize_group_request ac->ac_g_ex.fe_len = EXT4_SB(sb)->s_mb_group_prealloc ext4_mb_regular_allocator ext4_mb_choose_next_group ext4_mb_choose_next_group_best_avail mb_avg_fragment_size_order order = fls(len) - 2 = 29 ext4_mb_find_good_group_avg_frag_lists frag_list = &sbi->s_mb_avg_fragment_size[order] if (list_empty(frag_list)) // Trigger SOOB! At 4k block size, the length of the s_mb_avg_fragment_size list is 14, but an oversized s_mb_group_prealloc is set, causing slab-out-of-bounds to be triggered by an attempt to access an element at index 29. Add a new attr_id attr_clusters_in_group with values in the range [0, sbi->s_clusters_per_group] and declare mb_group_prealloc as that type to fix the issue. In addition avoid returning an order from mb_avg_fragment_size_order() greater than MB_NUM_ORDERS(sb) and reduce some useless loops.

Metrics

 

CVSS Version 4.0 CVSS Version 3.x CVSS Version 2.0

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CVSS 4.0 Severity and Vector Strings:

NIST: NVD

N/A

NVD assessment not yet provided.

CVSS 3.x Severity and Vector Strings:

NIST: NVD

Base Score:  5.5 MEDIUM

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

CVSS 2.0 Severity and Vector Strings:

NIST: NVD

Base Score: N/A

NVD assessment not yet provided.

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Hyperlink	Resource
https://git.kernel.org/stable/c/13df4d44a3aaabe61cd01d277b6ee23ead2a5206	Patch
https://git.kernel.org/stable/c/677ff4589f1501578fa903a25bb14831d0607992	Patch
https://git.kernel.org/stable/c/b829687ae1229224262bcabf49accfa2dbf8db06	Patch

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-787	Out-of-bounds Write	NIST

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Change History

2 change records found show changes

Initial Analysis by NIST 8/28/2024 3:45:37 PM

Action	Type	Old Value	New Value
Added	CPE Configuration		OR *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.5 up to (excluding) 6.6.36 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.7 up to (excluding) 6.9.7
Added	CVSS V3.1		NIST AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Added	CWE		NIST CWE-787
Changed	Reference Type	https://git.kernel.org/stable/c/13df4d44a3aaabe61cd01d277b6ee23ead2a5206 No Types Assigned	https://git.kernel.org/stable/c/13df4d44a3aaabe61cd01d277b6ee23ead2a5206 Patch
Changed	Reference Type	https://git.kernel.org/stable/c/677ff4589f1501578fa903a25bb14831d0607992 No Types Assigned	https://git.kernel.org/stable/c/677ff4589f1501578fa903a25bb14831d0607992 Patch
Changed	Reference Type	https://git.kernel.org/stable/c/b829687ae1229224262bcabf49accfa2dbf8db06 No Types Assigned	https://git.kernel.org/stable/c/b829687ae1229224262bcabf49accfa2dbf8db06 Patch

New CVE Received by NIST 7/12/2024 9:15:17 AM

Action	Type	Old Value	New Value
Added	Description		Record truncated, showing 500 of 2134 characters. View Entire Change Record In the Linux kernel, the following vulnerability has been resolved: ext4: fix slab-out-of-bounds in ext4_mb_find_good_group_avg_frag_lists() We can trigger a slab-out-of-bounds with the following commands: mkfs.ext4 -F /dev/$disk 10G mount /dev/$disk /tmp/test echo 2147483647 > /sys/fs/ext4/$disk/mb_group_prealloc echo test > /tmp/test/file && sync ================================================================== BUG: KASAN: slab-out-of-bounds in ext4_mb_find_good_group_avg_
Added	Reference		kernel.org https://git.kernel.org/stable/c/13df4d44a3aaabe61cd01d277b6ee23ead2a5206 [No types assigned]
Added	Reference		kernel.org https://git.kernel.org/stable/c/677ff4589f1501578fa903a25bb14831d0607992 [No types assigned]
Added	Reference		kernel.org https://git.kernel.org/stable/c/b829687ae1229224262bcabf49accfa2dbf8db06 [No types assigned]