CVE-2025-40137: Undefined Security Weakness

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

f2fs: fix to truncate first page in error path of f2fs_truncate()

syzbot reports a bug as below:

loop0: detected capacity change from 0 to 40427 F2FS-fs (loop0): Wrong SSA boundary, start(3584) end(4096) blocks(3072) F2FS-fs (loop0): Can't find valid F2FS filesystem in 1th superblock F2FS-fs (loop0): invalid crc value F2FS-fs (loop0): f2fs_convert_inline_folio: corrupted inline inode ino=3, i_addr[0]:0x1601, run fsck to fix. ------------[ cut here ]------------ kernel BUG at fs/inode.c:753! RIP: 0010:clear_inode+0x169/0x190 fs/inode.c:753 Call Trace: <TASK> evict+0x504/0x9c0 fs/inode.c:810 f2fs_fill_super+0x5612/0x6fa0 fs/f2fs/super.c:5047 get_tree_bdev_flags+0x40e/0x4d0 fs/super.c:1692 vfs_get_tree+0x8f/0x2b0 fs/super.c:1815 do_new_mount+0x2a2/0x9e0 fs/namespace.c:3808 do_mount fs/namespace.c:4136 [inline] __do_sys_mount fs/namespace.c:4347 [inline] __se_sys_mount+0x317/0x410 fs/namespace.c:4324 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f

During f2fs_evict_inode(), clear_inode() detects that we missed to truncate all page cache before destorying inode, that is because in below path, we will create page #0 in cache, but missed to drop it in error path, let's fix it.

- evict - f2fs_evict_inode - f2fs_truncate - f2fs_convert_inline_inode - f2fs_grab_cache_folio : create page #0 in cache - f2fs_convert_inline_folio : sanity check failed, return -EFSCORRUPTED - clear_inode detects that inode->i_data.nrpages is not zero