kernel/linux.git/fs/f2fs/sysfs.c, branch v6.19.11

f2fs: fix out-of-bounds access in sysfs attribute read/write

2026-02-19T15:33:25+00:00

commit 98ea0039dbfdd00e5cc1b9a8afa40434476c0955 upstream. Some f2fs sysfs attributes suffer from out-of-bounds memory access and incorrect handling of integer values whose size is not 4 bytes. For example: vm:~# echo 65537 > /sys/fs/f2fs/vde/carve_out vm:~# cat /sys/fs/f2fs/vde/carve_out 65537 vm:~# echo 4294967297 > /sys/fs/f2fs/vde/atgc_age_threshold vm:~# cat /sys/fs/f2fs/vde/atgc_age_threshold 1 carve_out maps to {struct f2fs_sb_info}->carve_out, which is a 8-bit integer. However, the sysfs interface allows setting it to a value larger than 255, resulting in an out-of-range update. atgc_age_threshold maps to {struct atgc_management}->age_threshold, which is a 64-bit integer, but its sysfs interface cannot correctly set values larger than UINT_MAX. The root causes are: 1. __sbi_store() treats all default values as unsigned int, which prevents updating integers larger than 4 bytes and causes out-of-bounds writes for integers smaller than 4 bytes. 2. f2fs_sbi_show() also assumes all default values are unsigned int, leading to out-of-bounds reads and incorrect access to integers larger than 4 bytes. This patch introduces {struct f2fs_attr}->size to record the actual size of the integer associated with each sysfs attribute. With this information, sysfs read and write operations can correctly access and update values according to their real data size, avoiding memory corruption and truncation. Fixes: b59d0bae6ca3 ("f2fs: add sysfs support for controlling the gc_thread") Cc: stable@kernel.org Signed-off-by: Jinbao Liu Signed-off-by: Yongpeng Yang Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim Signed-off-by: Greg Kroah-Hartman

f2fs: fix to check sysfs filename w/ gc_pin_file_thresh correctly

2026-02-19T15:33:25+00:00

commit 0eda086de85e140f53c6123a4c00662f4e614ee4 upstream. Sysfs entry name is gc_pin_file_thresh instead of gc_pin_file_threshold, fix it. Cc: stable@kernel.org Fixes: c521a6ab4ad7 ("f2fs: fix to limit gc_pin_file_threshold") Signed-off-by: Chao Yu Signed-off-by: Jaegeuk Kim Signed-off-by: Greg Kroah-Hartman

f2fs: add a sysfs entry to show max open zones

2025-12-04T02:00:04+00:00

This patch adds a sysfs entry showing the max zones that F2FS can write concurrently. Signed-off-by: Yongpeng Yang Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim

f2fs: revert summary entry count from 2048 to 512 in 16kb block support

2025-12-04T02:00:04+00:00

The recent increase in the number of Segment Summary Area (SSA) entries from 512 to 2048 was an unintentional change in logic of 16kb block support. This commit corrects the issue. To better utilize the space available from the erroneous 2048-entry calculation, we are implementing a solution to share the currently unused SSA space with neighboring segments. This enhances overall SSA utilization without impacting the established 8MB segment size. Fixes: d7e9a9037de2 ("f2fs: Support Block Size == Page Size") Signed-off-by: Daeho Jeong Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim

f2fs: add missing dput() when printing the donation list

2025-10-03T03:16:10+00:00

We missed to call dput() on the grabbed dentry. Fixes: f1a49c1b112b ("f2fs: show the list of donation files") Reviewed-by: Daeho Jeong Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim

f2fs: fix wrong layout information on 16KB page

2025-09-09T19:33:43+00:00

This patch fixes to support different block size. Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim

f2fs: Use allocate_section_policy to control write priority in multi-devices setups

2025-08-29T20:48:47+00:00

Introduces two new sys nodes: allocate_section_hint and allocate_section_policy. The allocate_section_hint identifies the boundary between devices, measured in sections; it defaults to the end of the device for single storage setups, and the end of the first device for multiple storage setups. The allocate_section_policy determines the write strategy, with a default value of 0 for normal sequential write strategy. A value of 1 prioritizes writes before the allocate_section_hint, while a value of 2 prioritizes writes after it. This strategy addresses the issue where, despite F2FS supporting multiple devices, SOC vendors lack multi-devices support (currently only supporting zoned devices). As a workaround, multiple storage devices are mapped to a single dm device. Both this workaround and the F2FS multi-devices solution may require prioritizing writing to certain devices, such as a device with better performance or when switching is needed due to performance degradation near a device's end. For scenarios with more than two devices, sort them at mount time to utilize this feature. When using this feature with a single storage device, it has almost no impact. However, for configurations where multiple storage devices are mapped to the same dm device using F2FS, utilizing this feature can provide some optimization benefits. Therefore, I believe it should not be limited to just multi-devices usage. Signed-off-by: Liao Yuanhong Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim

f2fs: show the list of donation files

2025-08-20T17:45:00+00:00

This patch introduces a proc entry to show the currently enrolled donation files. - "File path" indicates a file. - "Status" a. "Donated" means the file is registed in the donation list by fadvise(offset, length, POSIX_FADV_NOREUSE) b. "Evicted" means the donated pages were reclaimed. - "Offset (kb)" and "Length (kb) show the registered donation range. - "Cached pages (kb)" shows the amount of cached pages in the inode page cache. For example, # of files : 2 File path Status Donation offset (kb) Donation size (kb) File cached size (kb) --- /local/test2 Donated 0 1048576 2097152 /local/test Evicted 0 1048576 1048576 Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim

f2fs: Add bggc_io_aware to adjust the priority of BG_GC when issuing IO

2025-08-20T17:44:10+00:00

Currently, we have encountered some issues while testing ZUFS. In situations near the storage limit (e.g., 50GB remaining), and after simulating fragmentation by repeatedly writing and deleting data, we found that application installation and startup tests conducted after idling for a few minutes take significantly longer several times that of traditional UFS. Tracing the operations revealed that the majority of I/Os were issued by background GC, which blocks normal I/O operations. Under normal circumstances, ZUFS indeed requires more background GC and employs a more aggressive GC strategy. However, I aim to find a way to minimize the impact on regular I/O operations under these near-limit conditions. To address this, I have introduced a bggc_io_aware feature, which controls the prioritization of background GC in the presence of I/Os. This switch can be adjusted at the framework level to implement different strategies. If set to AWARE_ALL_IO, all background GC operations will be skipped during active I/O issuance. The default option remains consistent with the current strategy, ensuring no change in behavior. Signed-off-by: Liao Yuanhong Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim

f2fs: add sysfs entry for effective lookup mode

2025-08-11T17:03:53+00:00

This commit introduces a new read-only sysfs entry at /sys/fs/f2fs//effective_lookup_mode. This entry displays the actual directory lookup mode F2FS is currently using. This is needed for debugging and verification, as the behavior is determined by both on-disk flags and mount options. Signed-off-by: Daniel Lee Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim