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Message-ID: <2025041813-CVE-2025-37785-e13d@gregkh> Date: Fri, 18 Apr 2025 09:02:14 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-cve-announce@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...nel.org> Subject: CVE-2025-37785: ext4: fix OOB read when checking dotdot dir From: Greg Kroah-Hartman <gregkh@...nel.org> 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 The Linux kernel CVE team has assigned CVE-2025-37785 to this issue. Affected and fixed versions =========================== Issue introduced in 2.6.19 with commit ac27a0ec112a089f1a5102bc8dffc79c8c815571 and fixed in 5.10.236 with commit e47f472a664d70a3d104a6c2a035cdff55a719b4 Issue introduced in 2.6.19 with commit ac27a0ec112a089f1a5102bc8dffc79c8c815571 and fixed in 5.15.180 with commit b7531a4f99c3887439d778afaf418d1a01a5f01b Issue introduced in 2.6.19 with commit ac27a0ec112a089f1a5102bc8dffc79c8c815571 and fixed in 6.1.134 with commit 89503e5eae64637d0fa2218912b54660effe7d93 Issue introduced in 2.6.19 with commit ac27a0ec112a089f1a5102bc8dffc79c8c815571 and fixed in 6.6.87 with commit 52a5509ab19a5d3afe301165d9b5787bba34d842 Issue introduced in 2.6.19 with commit ac27a0ec112a089f1a5102bc8dffc79c8c815571 and fixed in 6.12.23 with commit b47584c556444cf7acb66b26a62cbc348eb92b78 Issue introduced in 2.6.19 with commit ac27a0ec112a089f1a5102bc8dffc79c8c815571 and fixed in 6.13.11 with commit ac28c5684c1cdab650a7e5065b19e91577d37a4b Issue introduced in 2.6.19 with commit ac27a0ec112a089f1a5102bc8dffc79c8c815571 and fixed in 6.14.2 with commit 53bc45da8d8da92ec07877f5922b130562eb4b00 Issue introduced in 2.6.19 with commit ac27a0ec112a089f1a5102bc8dffc79c8c815571 and fixed in 6.15-rc1 with commit d5e206778e96e8667d3bde695ad372c296dc9353 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2025-37785 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: fs/ext4/dir.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/e47f472a664d70a3d104a6c2a035cdff55a719b4 https://git.kernel.org/stable/c/b7531a4f99c3887439d778afaf418d1a01a5f01b https://git.kernel.org/stable/c/89503e5eae64637d0fa2218912b54660effe7d93 https://git.kernel.org/stable/c/52a5509ab19a5d3afe301165d9b5787bba34d842 https://git.kernel.org/stable/c/b47584c556444cf7acb66b26a62cbc348eb92b78 https://git.kernel.org/stable/c/ac28c5684c1cdab650a7e5065b19e91577d37a4b https://git.kernel.org/stable/c/53bc45da8d8da92ec07877f5922b130562eb4b00 https://git.kernel.org/stable/c/d5e206778e96e8667d3bde695ad372c296dc9353
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