CVE-2024-42297

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

f2fs: fix to don't dirty inode for readonly filesystem

syzbot reports f2fs bug as below:

kernel BUG at fs/f2fs/inode.c:933!

RIP: 0010:f2fs_evict_inode+0x1576/0x1590 fs/f2fs/inode.c:933

Call Trace:

evict+0x2a4/0x620 fs/inode.c:664

dispose_list fs/inode.c:697 [inline]

evict_inodes+0x5f8/0x690 fs/inode.c:747

generic_shutdown_super+0x9d/0x2c0 fs/super.c:675

kill_block_super+0x44/0x90 fs/super.c:1667

kill_f2fs_super+0x303/0x3b0 fs/f2fs/super.c:4894

deactivate_locked_super+0xc1/0x130 fs/super.c:484

cleanup_mnt+0x426/0x4c0 fs/namespace.c:1256

task_work_run+0x24a/0x300 kernel/task_work.c:180

ptrace_notify+0x2cd/0x380 kernel/signal.c:2399

ptrace_report_syscall include/linux/ptrace.h:411 [inline]

ptrace_report_syscall_exit include/linux/ptrace.h:473 [inline]

syscall_exit_work kernel/entry/common.c:251 [inline]

syscall_exit_to_user_mode_prepare kernel/entry/common.c:278 [inline]

__syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]

syscall_exit_to_user_mode+0x15c/0x280 kernel/entry/common.c:296

do_syscall_64+0x50/0x110 arch/x86/entry/common.c:88

entry_SYSCALL_64_after_hwframe+0x63/0x6b

The root cause is:

- do_sys_open

- f2fs_lookup

- __f2fs_find_entry

- f2fs_i_depth_write

- f2fs_mark_inode_dirty_sync

- f2fs_dirty_inode

- set_inode_flag(inode, FI_DIRTY_INODE)

- umount

- kill_f2fs_super

- kill_block_super

- generic_shutdown_super

- sync_filesystem

: sb is readonly, skip sync_filesystem()

- evict_inodes

- iput

- f2fs_evict_inode

- f2fs_bug_on(sbi, is_inode_flag_set(inode, FI_DIRTY_INODE))

: trigger kernel panic

When we try to repair i_current_depth in readonly filesystem, let's

skip dirty inode to avoid panic in later f2fs_evict_inode().