f2fs: fix to do sanity check on inode type during garbage collection

commit 9056d6489f5a41cfbb67f719d2c0ce61ead72d9f upstream.

As report by Wenqing Liu in bugzilla:

https://bugzilla.kernel.org/show_bug.cgi?id=215231

- Overview
kernel NULL pointer dereference triggered  in folio_mark_dirty() when mount and operate on a crafted f2fs image

- Reproduce
tested on kernel 5.16-rc3, 5.15.X under root

1. mkdir mnt
2. mount -t f2fs tmp1.img mnt
3. touch tmp
4. cp tmp mnt

F2FS-fs (loop0): sanity_check_inode: inode (ino=49) extent info [5942, 4294180864, 4] is incorrect, run fsck to fix
F2FS-fs (loop0): f2fs_check_nid_range: out-of-range nid=31340049, run fsck to fix.
BUG: kernel NULL pointer dereference, address: 0000000000000000
 folio_mark_dirty+0x33/0x50
 move_data_page+0x2dd/0x460 [f2fs]
 do_garbage_collect+0xc18/0x16a0 [f2fs]
 f2fs_gc+0x1d3/0xd90 [f2fs]
 f2fs_balance_fs+0x13a/0x570 [f2fs]
 f2fs_create+0x285/0x840 [f2fs]
 path_openat+0xe6d/0x1040
 do_filp_open+0xc5/0x140
 do_sys_openat2+0x23a/0x310
 do_sys_open+0x57/0x80

The root cause is for special file: e.g. character, block, fifo or socket file,
f2fs doesn't assign address space operations pointer array for mapping->a_ops field,
so, in a fuzzed image, SSA table indicates a data block belong to special file, when
f2fs tries to migrate that block, it causes NULL pointer access once move_data_page()
calls a_ops->set_dirty_page().

Cc: stable@vger.kernel.org
Reported-by: Wenqing Liu <wenqingliu0120@gmail.com>
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Kazunori Kobayashi <kazunori.kobayashi@miraclelinux.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index c2e4c6ce2cf79d6bdbeb77b6f0e84f98c3880961..1f86b456ba7a53df019b82b47b51f56022395786 100644 (file)
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -841,7 +841,8 @@ next_step:
 
                if (phase == 3) {
                        inode = f2fs_iget(sb, dni.ino);
-                       if (IS_ERR(inode) || is_bad_inode(inode))
+                       if (IS_ERR(inode) || is_bad_inode(inode) ||
+                                       special_file(inode->i_mode))
                                continue;
 
                        /* if encrypted inode, let's go phase 3 */