CVE-2024-35844 — f2fs: compress: fix reserve_cblocks counting error when out of space

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

f2fs: compress: fix reserve_cblocks counting error when out of space

When a file only needs one direct_node, performing the following operations will cause the file to be unrepairable:

unisoc # ./f2fs_io compress test.apk unisoc #df -h | grep dm-48 /dev/block/dm-48 112G 112G 1.2M 100% /data

unisoc # ./f2fs_io release_cblocks test.apk 924 unisoc # df -h | grep dm-48 /dev/block/dm-48 112G 112G 4.8M 100% /data

unisoc # dd if=/dev/random of=file4 bs=1M count=3 3145728 bytes (3.0 M) copied, 0.025 s, 120 M/s unisoc # df -h | grep dm-48 /dev/block/dm-48 112G 112G 1.8M 100% /data

unisoc # ./f2fs_io reserve_cblocks test.apk F2FS_IOC_RESERVE_COMPRESS_BLOCKS failed: No space left on device

adb reboot unisoc # df -h | grep dm-48 /dev/block/dm-48 112G 112G 11M 100% /data unisoc # ./f2fs_io reserve_cblocks test.apk 0

This is because the file has only one direct_node. After returning to -ENOSPC, reserved_blocks += ret will not be executed. As a result, the reserved_blocks at this time is still 0, which is not the real number of reserved blocks. Therefore, fsck cannot be set to repair the file.

After this patch, the fsck flag will be set to fix this problem.

unisoc # df -h | grep dm-48 /dev/block/dm-48 112G 112G 1.8M 100% /data unisoc # ./f2fs_io reserve_cblocks test.apk F2FS_IOC_RESERVE_COMPRESS_BLOCKS failed: No space left on device

adb reboot then fsck will be executed unisoc # df -…

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CVE-2024-35844 — f2fs: compress: fix reserve_cblocks counting error when out of space