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Yongjian Sun 419812d8e6 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 2026-01-08 10:14:15 +01:00
arch lib/crypto: x86/blake2s: Fix 32-bit arg treated as 64-bit 2026-01-08 10:14:14 +01:00
block block: rate-limit capacity change info log 2026-01-08 10:14:14 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: asymmetric_keys - prevent overflow in asymmetric_key_generate_id 2025-12-18 13:54:47 +01:00
Documentation nfsd: rename nfsd_serv_ prefixed methods and variables with nfsd_net_ 2026-01-08 10:14:09 +01:00
drivers tpm: Cap the number of PCR banks 2026-01-08 10:14:15 +01:00
fs ext4: fix incorrect group number assertion in mb_check_buddy 2026-01-08 10:14:15 +01:00
include tpm: Cap the number of PCR banks 2026-01-08 10:14:15 +01:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:33:50 +02:00
io_uring io_uring: fix filename leak in __io_openat_prep() 2026-01-08 10:14:13 +01:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel kallsyms: Fix wrong "big" kernel symbol type read from procfs 2026-01-08 10:14:14 +01:00
lib lib/vsprintf: Check pointer before dereferencing in time_and_date() 2025-12-18 13:54:57 +01:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm shmem: fix recovery on rename failures 2026-01-08 10:13:54 +01:00
net net/hsr: fix NULL pointer dereference in prp_get_untagged_frame() 2026-01-08 10:14:08 +01:00
rust rust: kbuild: workaround rustdoc doctests modifier bug 2025-11-24 10:36:07 +01:00
samples samples: work around glibc redefining some of our defines wrong 2025-12-12 18:37:21 +01:00
scripts kbuild: Use objtree for module signing key path 2026-01-08 10:13:56 +01:00
security KEYS: trusted: Fix a memory leak in tpm2_load_cmd 2026-01-08 10:14:13 +01:00
sound ASoC: ak4458: remove the reset operation in probe and remove 2026-01-08 10:14:08 +01:00
tools ktest.pl: Fix uninitialized var in config-bisect.pl 2026-01-08 10:14:15 +01:00
usr kbuild: uapi: Strip comments before size type check 2025-11-13 15:34:35 -05:00
virt KVM: guest_memfd: Remove bindings on memslot deletion when gmem is dying 2025-11-24 10:36:06 +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: give Clippy the minimum supported Rust version 2025-08-01 09:48:44 +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 staging: rtl8712: Remove driver using deprecated API wext 2025-12-07 06:25:02 +09:00
Makefile Linux 6.12.63 2025-12-18 13:55:23 +01:00
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.