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Yongjian Sun 2930d9cb9c ext4: fix incorrect group number assertion in mb_check_buddy 
commit 3f7a79d05c upstream.

When the MB_CHECK_ASSERT macro is enabled, an assertion failure can
occur in __mb_check_buddy when checking preallocated blocks (pa) in
a block group:

Assertion failure in mb_free_blocks() : "groupnr == e4b->bd_group"

This happens when a pa at the very end of a block group (e.g.,
pa_pstart=32765, pa_len=3 in a group of 32768 blocks) becomes
exhausted - its pa_pstart is advanced by pa_len to 32768, which
lies in the next block group. If this exhausted pa (with pa_len == 0)
is still in the bb_prealloc_list during the buddy check, the assertion
incorrectly flags it as belonging to the wrong group. A possible
sequence is as follows:

ext4_mb_new_blocks
  ext4_mb_release_context
    pa->pa_pstart += EXT4_C2B(sbi, ac->ac_b_ex.fe_len)
    pa->pa_len -= ac->ac_b_ex.fe_len

	                 __mb_check_buddy
                           for each pa in group
                             ext4_get_group_no_and_offset
                             MB_CHECK_ASSERT(groupnr == e4b->bd_group)

To fix this, we modify the check to skip block group validation for
exhausted preallocations (where pa_len == 0). Such entries are in a
transitional state and will be removed from the list soon, so they
should not trigger an assertion. This change prevents the false
positive while maintaining the integrity of the checks for active
allocations.

Fixes: c9de560ded ("ext4: Add multi block allocator for ext4")
Signed-off-by: Yongjian Sun <sunyongjian1@huawei.com>
Reviewed-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Message-ID: <20251106060614.631382-2-sunyongjian@huaweicloud.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2026-01-19 13:09:49 +01:00
arch lib/crypto: x86/blake2s: Fix 32-bit arg treated as 64-bit 2026-01-19 13:09:49 +01:00
block block: rate-limit capacity change info log 2026-01-19 13:09:49 +01:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: asymmetric_keys - prevent overflow in asymmetric_key_generate_id 2026-01-19 13:09:24 +01:00
Documentation fs_context: drop the unused lsm_flags member 2026-01-19 13:09:38 +01:00
drivers floppy: fix for PAGE_SIZE != 4KB 2026-01-19 13:09:49 +01:00
fs
include efi/cper: align ARM CPER type with UEFI 2.9A/2.10 specs 2026-01-19 13:09:40 +01:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:21:45 +02:00
io_uring io_uring: fix possible deadlock in io_register_iowq_max_workers() 2024-11-17 15:06:25 +01:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:05:26 +01:00
kernel livepatch: Match old_sympos 0 and 1 in klp_find_func() 2026-01-19 13:09:42 +01:00
lib lib/vsprintf: Check pointer before dereferencing in time_and_date() 2026-01-19 13:09:29 +01:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm/secretmem: fix use-after-free race in fault handler 2025-12-07 06:09:32 +09:00
net net/hsr: fix NULL pointer dereference in prp_get_untagged_frame() 2026-01-19 13:09:46 +01:00
samples samples: mei: Fix building on musl libc 2025-08-28 16:24:07 +02:00
scripts Makefile.compiler: replace cc-ifversion with compiler-specific macros 2025-12-07 06:09:32 +09:00
security KEYS: trusted: Fix a memory leak in tpm2_load_cmd 2026-01-19 13:09:48 +01:00
sound ALSA: usb-mixer: us16x08: validate meter packet indices 2026-01-19 13:09:46 +01:00
tools ktest.pl: Fix uninitialized var in config-bisect.pl 2026-01-19 13:09:49 +01:00
usr kbuild: hdrcheck: fix cross build with clang 2025-06-27 11:05:22 +01:00
virt KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin() 2024-10-22 15:40:41 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Remove *.orig pattern from .gitignore 2024-10-17 15:11:10 +02:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS staging: rtl8712: Remove driver using deprecated API wext 2025-12-07 06:09:36 +09:00
Makefile Linux 5.15.197 2025-12-07 06:09:37 +09:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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 Restructured Text 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.