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Linux kernel source tree
d5e206778e
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:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| 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.