CVE-2024-56586

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

f2fs: fix f2fs_bug_on when uninstalling filesystem call f2fs_evict_inode.

creating a large files during checkpoint disable until it runs out of space and then delete it, then remount to enable checkpoint again, and then unmount the filesystem triggers the f2fs_bug_on as below:

————[ cut here ]———— kernel BUG at fs/f2fs/inode.c:896! CPU: 2 UID: 0 PID: 1286 Comm: umount Not tainted 6.11.0-rc7-dirty #360 Oops: invalid opcode: 0000 [#1] PREEMPT SMP NOPTI RIP: 0010:f2fs_evict_inode+0x58c/0x610 Call Trace: __die_body+0x15/0x60 die+0x33/0x50 do_trap+0x10a/0x120 f2fs_evict_inode+0x58c/0x610 do_error_trap+0x60/0x80 f2fs_evict_inode+0x58c/0x610 exc_invalid_op+0x53/0x60 f2fs_evict_inode+0x58c/0x610 asm_exc_invalid_op+0x16/0x20 f2fs_evict_inode+0x58c/0x610 evict+0x101/0x260 dispose_list+0x30/0x50 evict_inodes+0x140/0x190 generic_shutdown_super+0x2f/0x150 kill_block_super+0x11/0x40 kill_f2fs_super+0x7d/0x140 deactivate_locked_super+0x2a/0x70 cleanup_mnt+0xb3/0x140 task_work_run+0x61/0x90

The root cause is: creating large files during disable checkpoint period results in not enough free segments, so when writing back root inode will failed in f2fs_enable_checkpoint. When umount the file system after enabling checkpoint, the root inode is dirty in f2fs_evict_inode function, which triggers BUG_ON. The steps to reproduce are as follows:

dd if=/dev/zero of=f2fs.img bs=1M count=55 mount f2fs.img f2fs_dir -o checkpoint=disable:10% dd if=/dev/zero of=big bs=1M count=50 sync rm big mount -o remount,checkpoint=enable f2fs_dir umount f2fs_dir

Lets redirty inode when there is not free segments during checkpoint is disable.

Affected Software

References

• https://git.kernel.org/stable/c/9669b28f81e0ec6305af7773846fbe2cef1e7d61
• https://git.kernel.org/stable/c/9e28513fd2858911dcf47b84160a8824587536b6
• https://git.kernel.org/stable/c/a365de2fbfbe1e6740bfb75ab5c3245cf7bbe4d7
• https://git.kernel.org/stable/c/ac8aaf78bd039fa1be0acaa8e84a56499f79d721
• https://git.kernel.org/stable/c/d5c367ef8287fb4d235c46a2f8c8d68715f3a0ca
• https://git.kernel.org/stable/c/dff561e4060d28edc9a2960d4a87f3c945a96aa3
• https://git.kernel.org/stable/c/ef517d2d21c3d8e2ad35b2bb728bd1c90a31e617