From: Chao Yu chao@kernel.org

mainline inclusion from mainline-v5.16-rc1 commit 9056d6489f5a41cfbb67f719d2c0ce61ead72d9f category: bugfix bugzilla: 186264 CVE: CVE-2021-44879

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

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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: Guo Xuenan guoxuenan@huawei.com Reviewed-by: Xiu Jianfeng xiujianfeng@huawei.com Reviewed-by: fang wei fangwei1@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- fs/f2fs/gc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c index 700c39ec99f5a..f4f7b8feebefc 100644 --- a/fs/f2fs/gc.c +++ b/fs/f2fs/gc.c @@ -953,7 +953,8 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,

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 (!down_write_trylock(