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Acs, Jakub b47584c556 ext4: fix OOB read when checking dotdot dir 
commit d5e206778e upstream.

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

Fixes: ac27a0ec11 ("[PATCH] ext4: initial copy of files from ext3")
Signed-off-by: Jakub Acs <acsjakub@amazon.de>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: linux-ext4@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Mahmoud Adam <mngyadam@amazon.com>
Cc: stable@vger.kernel.org
Cc: security@kernel.org
Link: https://patch.msgid.link/b3ae36a6794c4a01944c7d70b403db5b@amazon.de
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-04-10 14:39:39 +02:00
arch arm64: Don't call NULL in do_compat_alignment_fixup() 2025-04-10 14:39:39 +02:00
block block: fix 'kmem_cache of name 'bio-108' already exists' 2025-03-22 12:54:21 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: api - Fix larval relookup type and mask 2025-04-10 14:39:20 +02:00
Documentation dt-bindings: vendor-prefixes: add GOcontroll 2025-04-10 14:39:13 +02:00
drivers wifi: mt76: mt7921: fix kernel panic due to null pointer dereference 2025-04-10 14:39:39 +02:00
fs ext4: fix OOB read when checking dotdot dir 2025-04-10 14:39:39 +02:00
include uprobes/x86: Harden uretprobe syscall trampoline check 2025-04-10 14:39:37 +02:00
init rust: Disallow BTF generation with Rust + LTO 2025-03-22 12:54:23 -07:00
io_uring io_uring/net: fix sendzc double notif flush 2025-03-28 22:03:32 +01:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-05 14:03:02 +01:00
kernel tracing/osnoise: Fix possible recursive locking for cpus_read_lock() 2025-04-10 14:39:39 +02:00
lib rust: fix signature of rust_fmt_argument 2025-04-10 14:39:20 +02:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm/gup: reject FOLL_SPLIT_PMD with hugetlb VMAs 2025-04-10 14:39:39 +02:00
net wifi: mac80211: Fix sparse warning for monitor_sdata 2025-04-10 14:39:36 +02:00
rust rust: Fix enabling Rust and building with GCC for LoongArch 2025-04-10 14:39:36 +02:00
samples rust: treewide: switch to the kernel Vec type 2025-03-13 13:01:46 +01:00
scripts kbuild: deb-pkg: don't set KBUILD_BUILD_VERSION unconditionally 2025-04-10 14:39:35 +02:00
security smack: ipv4/ipv6: tcp/dccp/sctp: fix incorrect child socket label 2025-04-10 14:39:10 +02:00
sound ALSA: hda/realtek: Fix built-in mic on another ASUS VivoBook model 2025-04-10 14:39:33 +02:00
tools tools/power turbostat: report CoreThr per measurement interval 2025-04-10 14:39:35 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: x86: switch hugepage recovery thread to vhost_task 2024-12-05 14:02:43 +01:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: enable Clippy's check-private-items 2025-03-13 13:01:42 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: add entry for the Rust alloc module 2025-03-13 13:01:47 +01:00
Makefile Linux 6.12.22 2025-04-07 10:08:37 +02:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.