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Chao Yu 0df713a9c0 f2fs: fix to avoid updating compression context during writeback 
commit 10b591e7fb upstream.

Bai, Shuangpeng <sjb7183@psu.edu> reported a bug as below:

Oops: divide error: 0000 [#1] SMP KASAN PTI
CPU: 0 UID: 0 PID: 11441 Comm: syz.0.46 Not tainted 6.17.0 #1 PREEMPT(full)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
RIP: 0010:f2fs_all_cluster_page_ready+0x106/0x550 fs/f2fs/compress.c:857
Call Trace:
 <TASK>
 f2fs_write_cache_pages fs/f2fs/data.c:3078 [inline]
 __f2fs_write_data_pages fs/f2fs/data.c:3290 [inline]
 f2fs_write_data_pages+0x1c19/0x3600 fs/f2fs/data.c:3317
 do_writepages+0x38e/0x640 mm/page-writeback.c:2634
 filemap_fdatawrite_wbc mm/filemap.c:386 [inline]
 __filemap_fdatawrite_range mm/filemap.c:419 [inline]
 file_write_and_wait_range+0x2ba/0x3e0 mm/filemap.c:794
 f2fs_do_sync_file+0x6e6/0x1b00 fs/f2fs/file.c:294
 generic_write_sync include/linux/fs.h:3043 [inline]
 f2fs_file_write_iter+0x76e/0x2700 fs/f2fs/file.c:5259
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x7e9/0xe00 fs/read_write.c:686
 ksys_write+0x19d/0x2d0 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf7/0x470 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The bug was triggered w/ below race condition:

fsync				setattr			ioctl
- f2fs_do_sync_file
 - file_write_and_wait_range
  - f2fs_write_cache_pages
  : inode is non-compressed
  : cc.cluster_size =
    F2FS_I(inode)->i_cluster_size = 0
   - tag_pages_for_writeback
				- f2fs_setattr
				 - truncate_setsize
				 - f2fs_truncate
							- f2fs_fileattr_set
							 - f2fs_setflags_common
							  - set_compress_context
							  : F2FS_I(inode)->i_cluster_size = 4
							  : set_inode_flag(inode, FI_COMPRESSED_FILE)
   - f2fs_compressed_file
   : return true
   - f2fs_all_cluster_page_ready
   : "pgidx % cc->cluster_size" trigger dividing 0 issue

Let's change as below to fix this issue:
- introduce a new atomic type variable .writeback in structure f2fs_inode_info
to track the number of threads which calling f2fs_write_cache_pages().
- use .i_sem lock to protect .writeback update.
- check .writeback before update compression context in f2fs_setflags_common()
to avoid race w/ ->writepages.

Fixes: 4c8ff7095b ("f2fs: support data compression")
Cc: stable@kernel.org
Reported-by: Bai, Shuangpeng <sjb7183@psu.edu>
Tested-by: Bai, Shuangpeng <sjb7183@psu.edu>
Closes: https://lore.kernel.org/lkml/44D8F7B3-68AD-425F-9915-65D27591F93F@psu.edu
Signed-off-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 12:57:16 +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 to avoid updating compression context during writeback 2026-01-02 12:57:16 +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.