In the Linux kernel, the following vulnerability has been resolved: ext4: fix OOB read when checking dotdot dir Mounting a corrupted filesystem with directory which contains '.' dir entry with rec_len == block size results in out-of-bounds read (later on, when the corrupted directory is removed). ext4_empty_dir() assumes every ext4 directory contains at least '.' and '..' as directory entries in the first data block. It first loads the '.' dir entry, performs sanity checks by calling ext4_check_dir_entry() and then uses its rec_len member to compute the location of '..' dir entry (in ext4_next_entry). It assumes the '..' dir entry fits into the same data block. If the rec_len of '.' is precisely one block (4KB), it slips through the sanity checks (it is considered the last directory entry in the data block) and leaves "struct ext4_dir_entry_2 *de" point exactly past the memory slot allocated to the data block. The following call to ext4_check_dir_entry() on new value of de then dereferences this pointer which results in out-of-bounds mem access. Fix this by extending __ext4_check_dir_entry() to check for '.' dir entries that reach the end of data block. Make sure to ignore the phony dir entries for checksum (by checking name_len for non-zero). Note: This is reported by KASAN as use-after-free in case another structure was recently freed from the slot past the bound, but it is really an OOB read. This issue was found by syzkaller tool. Call Trace: [ 38.594108] BUG: KASAN: slab-use-after-free in __ext4_check_dir_entry+0x67e/0x710 [ 38.594649] Read of size 2 at addr ffff88802b41a004 by task syz-executor/5375 [ 38.595158] [ 38.595288] CPU: 0 UID: 0 PID: 5375 Comm: syz-executor Not tainted 6.14.0-rc7 #1 [ 38.595298] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 [ 38.595304] Call Trace: [ 38.595308] <TASK> [ 38.595311] dump_stack_lvl+0xa7/0xd0 [ 38.595325] print_address_description.constprop.0+0x2c/0x3f0 [ 38.595339] ? __ext4_check_dir_entry+0x67e/0x710 [ 38.595349] print_report+0xaa/0x250 [ 38.595359] ? __ext4_check_dir_entry+0x67e/0x710 [ 38.595368] ? kasan_addr_to_slab+0x9/0x90 [ 38.595378] kasan_report+0xab/0xe0 [ 38.595389] ? __ext4_check_dir_entry+0x67e/0x710 [ 38.595400] __ext4_check_dir_entry+0x67e/0x710 [ 38.595410] ext4_empty_dir+0x465/0x990 [ 38.595421] ? __pfx_ext4_empty_dir+0x10/0x10 [ 38.595432] ext4_rmdir.part.0+0x29a/0xd10 [ 38.595441] ? __dquot_initialize+0x2a7/0xbf0 [ 38.595455] ? __pfx_ext4_rmdir.part.0+0x10/0x10 [ 38.595464] ? __pfx___dquot_initialize+0x10/0x10 [ 38.595478] ? down_write+0xdb/0x140 [ 38.595487] ? __pfx_down_write+0x10/0x10 [ 38.595497] ext4_rmdir+0xee/0x140 [ 38.595506] vfs_rmdir+0x209/0x670 [ 38.595517] ? lookup_one_qstr_excl+0x3b/0x190 [ 38.595529] do_rmdir+0x363/0x3c0 [ 38.595537] ? __pfx_do_rmdir+0x10/0x10 [ 38.595544] ? strncpy_from_user+0x1ff/0x2e0 [ 38.595561] __x64_sys_unlinkat+0xf0/0x130 [ 38.595570] do_syscall_64+0x5b/0x180 [ 38.595583] entry_SYSCALL_64_after_hwframe+0x76/0x7e
History

Tue, 29 Apr 2025 17:15:00 +0000

Type Values Removed Values Added
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel

Tue, 22 Apr 2025 02:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-125
Metrics cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

cvssV3_1

{'score': 7.1, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H'}


Sat, 19 Apr 2025 02:00:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Moderate


Fri, 18 Apr 2025 07:15:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: ext4: fix OOB read when checking dotdot dir Mounting a corrupted filesystem with directory which contains '.' dir entry with rec_len == block size results in out-of-bounds read (later on, when the corrupted directory is removed). ext4_empty_dir() assumes every ext4 directory contains at least '.' and '..' as directory entries in the first data block. It first loads the '.' dir entry, performs sanity checks by calling ext4_check_dir_entry() and then uses its rec_len member to compute the location of '..' dir entry (in ext4_next_entry). It assumes the '..' dir entry fits into the same data block. If the rec_len of '.' is precisely one block (4KB), it slips through the sanity checks (it is considered the last directory entry in the data block) and leaves "struct ext4_dir_entry_2 *de" point exactly past the memory slot allocated to the data block. The following call to ext4_check_dir_entry() on new value of de then dereferences this pointer which results in out-of-bounds mem access. Fix this by extending __ext4_check_dir_entry() to check for '.' dir entries that reach the end of data block. Make sure to ignore the phony dir entries for checksum (by checking name_len for non-zero). Note: This is reported by KASAN as use-after-free in case another structure was recently freed from the slot past the bound, but it is really an OOB read. This issue was found by syzkaller tool. Call Trace: [ 38.594108] BUG: KASAN: slab-use-after-free in __ext4_check_dir_entry+0x67e/0x710 [ 38.594649] Read of size 2 at addr ffff88802b41a004 by task syz-executor/5375 [ 38.595158] [ 38.595288] CPU: 0 UID: 0 PID: 5375 Comm: syz-executor Not tainted 6.14.0-rc7 #1 [ 38.595298] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 [ 38.595304] Call Trace: [ 38.595308] <TASK> [ 38.595311] dump_stack_lvl+0xa7/0xd0 [ 38.595325] print_address_description.constprop.0+0x2c/0x3f0 [ 38.595339] ? __ext4_check_dir_entry+0x67e/0x710 [ 38.595349] print_report+0xaa/0x250 [ 38.595359] ? __ext4_check_dir_entry+0x67e/0x710 [ 38.595368] ? kasan_addr_to_slab+0x9/0x90 [ 38.595378] kasan_report+0xab/0xe0 [ 38.595389] ? __ext4_check_dir_entry+0x67e/0x710 [ 38.595400] __ext4_check_dir_entry+0x67e/0x710 [ 38.595410] ext4_empty_dir+0x465/0x990 [ 38.595421] ? __pfx_ext4_empty_dir+0x10/0x10 [ 38.595432] ext4_rmdir.part.0+0x29a/0xd10 [ 38.595441] ? __dquot_initialize+0x2a7/0xbf0 [ 38.595455] ? __pfx_ext4_rmdir.part.0+0x10/0x10 [ 38.595464] ? __pfx___dquot_initialize+0x10/0x10 [ 38.595478] ? down_write+0xdb/0x140 [ 38.595487] ? __pfx_down_write+0x10/0x10 [ 38.595497] ext4_rmdir+0xee/0x140 [ 38.595506] vfs_rmdir+0x209/0x670 [ 38.595517] ? lookup_one_qstr_excl+0x3b/0x190 [ 38.595529] do_rmdir+0x363/0x3c0 [ 38.595537] ? __pfx_do_rmdir+0x10/0x10 [ 38.595544] ? strncpy_from_user+0x1ff/0x2e0 [ 38.595561] __x64_sys_unlinkat+0xf0/0x130 [ 38.595570] do_syscall_64+0x5b/0x180 [ 38.595583] entry_SYSCALL_64_after_hwframe+0x76/0x7e
Title ext4: fix OOB read when checking dotdot dir
References

cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2025-04-18T07:01:27.393Z

Updated: 2025-04-18T07:01:27.393Z

Reserved: 2025-04-16T04:51:23.940Z

Link: CVE-2025-37785

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Analyzed

Published: 2025-04-18T07:15:42.693

Modified: 2025-04-29T16:56:25.337

Link: CVE-2025-37785

cve-icon Redhat

Severity : Moderate

Publid Date: 2025-04-18T00:00:00Z

Links: CVE-2025-37785 - Bugzilla