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Xiaole He 57e36f84f2 f2fs: fix uninitialized one_time_gc in victim_sel_policy 
commit 392711ef18 upstream.

The one_time_gc field in struct victim_sel_policy is conditionally
initialized but unconditionally read, leading to undefined behavior
that triggers UBSAN warnings.

In f2fs_get_victim() at fs/f2fs/gc.c:774, the victim_sel_policy
structure is declared without initialization:

    struct victim_sel_policy p;

The field p.one_time_gc is only assigned when the 'one_time' parameter
is true (line 789):

    if (one_time) {
        p.one_time_gc = one_time;
        ...
    }

However, this field is unconditionally read in subsequent get_gc_cost()
at line 395:

    if (p->one_time_gc && (valid_thresh_ratio < 100) && ...)

When one_time is false, p.one_time_gc contains uninitialized stack
memory. Hence p.one_time_gc is an invalid bool value.

UBSAN detects this invalid bool value:

    UBSAN: invalid-load in fs/f2fs/gc.c:395:7
    load of value 77 is not a valid value for type '_Bool'
    CPU: 3 UID: 0 PID: 1297 Comm: f2fs_gc-252:16 Not tainted 6.18.0-rc3
    #5 PREEMPT(voluntary)
    Hardware name: OpenStack Foundation OpenStack Nova,
    BIOS 1.13.0-1ubuntu1.1 04/01/2014
    Call Trace:
     <TASK>
     dump_stack_lvl+0x70/0x90
     dump_stack+0x14/0x20
     __ubsan_handle_load_invalid_value+0xb3/0xf0
     ? dl_server_update+0x2e/0x40
     ? update_curr+0x147/0x170
     f2fs_get_victim.cold+0x66/0x134 [f2fs]
     ? sched_balance_newidle+0x2ca/0x470
     ? finish_task_switch.isra.0+0x8d/0x2a0
     f2fs_gc+0x2ba/0x8e0 [f2fs]
     ? _raw_spin_unlock_irqrestore+0x12/0x40
     ? __timer_delete_sync+0x80/0xe0
     ? timer_delete_sync+0x14/0x20
     ? schedule_timeout+0x82/0x100
     gc_thread_func+0x38b/0x860 [f2fs]
     ? gc_thread_func+0x38b/0x860 [f2fs]
     ? __pfx_autoremove_wake_function+0x10/0x10
     kthread+0x10b/0x220
     ? __pfx_gc_thread_func+0x10/0x10 [f2fs]
     ? _raw_spin_unlock_irq+0x12/0x40
     ? __pfx_kthread+0x10/0x10
     ret_from_fork+0x11a/0x160
     ? __pfx_kthread+0x10/0x10
     ret_from_fork_asm+0x1a/0x30
     </TASK>

This issue is reliably reproducible with the following steps on a
100GB SSD /dev/vdb:

    mkfs.f2fs -f /dev/vdb
    mount /dev/vdb /mnt/f2fs_test
    fio --name=gc --directory=/mnt/f2fs_test --rw=randwrite \
        --bs=4k --size=8G --numjobs=12 --fsync=4 --runtime=10 \
        --time_based
    echo 1 > /sys/fs/f2fs/vdb/gc_urgent

The uninitialized value causes incorrect GC victim selection, leading
to unpredictable garbage collection behavior.

Fix by zero-initializing the entire victim_sel_policy structure to
ensure all fields have defined values.

Fixes: e791d00bd0 ("f2fs: add valid block ratio not to do excessive GC for one time GC")
Cc: stable@kernel.org
Signed-off-by: Xiaole He <hexiaole1994@126.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2026-01-02 12:57:17 +01:00
arch crash: let architecture decide crash memory export to iomem_resource 2026-01-02 12:57:11 +01:00
block block: Remove queue freezing from several sysfs store callbacks 2026-01-02 12:57:11 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: scatterwalk - Fix memcpy_sglist() to always succeed 2026-01-02 12:57:08 +01:00
Documentation dt-bindings: slimbus: fix warning from example 2026-01-02 12:57:14 +01:00
drivers scsi: ufs: core: Add ufshcd_update_evt_hist() for UFS suspend error 2026-01-02 12:57:16 +01:00
fs f2fs: fix uninitialized one_time_gc in victim_sel_policy 2026-01-02 12:57:17 +01:00
include mptcp: pm: ignore unknown endpoint flags 2026-01-02 12:57:12 +01:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring: fix filename leak in __io_openat_prep() 2026-01-02 12:57:06 +01:00
ipc namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
kernel crash: let architecture decide crash memory export to iomem_resource 2026-01-02 12:57:11 +01:00
lib lib/crypto: x86/blake2s: Fix 32-bit arg treated as 64-bit 2026-01-02 12:57:07 +01:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm mm/slab: introduce kvfree_rcu_barrier_on_cache() for cache destruction 2026-01-02 12:57:12 +01:00
net mptcp: avoid deadlock on fallback while reinjecting 2026-01-02 12:57:12 +01:00
rust rust: io: add typedef for phys_addr_t 2026-01-02 12:57:05 +01:00
samples samples: rust: fix endianness issue in rust_driver_pci 2026-01-02 12:57:05 +01:00
scripts kbuild: Use objtree for module signing key path 2026-01-02 12:56:40 +01:00
security tpm2-sessions: Fix out of range indexing in name_size 2026-01-02 12:57:11 +01:00
sound ASoC: ops: fix snd_soc_get_volsw for sx controls 2026-01-02 12:56:59 +01:00
tools selftests: mptcp: pm: ensure unknown flags are ignored 2026-01-02 12:57:12 +01:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt KVM: guest_memfd: Remove bindings on memslot deletion when gmem is dying 2025-11-04 09:16:53 -08:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.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 MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap 8 hotfixes. 4 are cc:stable, 7 are against mm/. 2025-11-26 12:38:05 -08:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.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: mark ISDN subsystem as orphan 2025-10-27 17:49:45 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS soc: fixes for 6.18, part 4 2025-11-28 09:57:31 -08:00
Makefile Linux 6.18.2 2025-12-18 14:03:43 +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.