On 09/08, Chao Yu wrote:
> Sometimes we can get a cached meta_inode which has no aops yet. Let's set it
> all the time to fix the below panic.
>
> Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
> Mem abort info:
> ESR = 0x0000000086000004
> EC = 0x21: IABT (current EL), IL = 32 bits
> SET = 0, FnV = 0
> EA = 0, S1PTW = 0
> FSC = 0x04: level 0 translation fault
> user pgtable: 4k pages, 48-bit VAs, pgdp=0000000109ee4000
> [0000000000000000] pgd=0000000000000000, p4d=0000000000000000
> Internal error: Oops: 86000004 [#1] PREEMPT SMP
> Modules linked in:
> CPU: 1 PID: 3045 Comm: syz-executor330 Not tainted 6.0.0-rc2-syzkaller-16455-ga41a877bc12d #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
> pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : 0x0
> lr : folio_mark_dirty+0xbc/0x208 mm/page-writeback.c:2748
> sp : ffff800012783970
> x29: ffff800012783970 x28: 0000000000000000 x27: ffff800012783b08
> x26: 0000000000000001 x25: 0000000000000400 x24: 0000000000000001
> x23: ffff0000c736e000 x22: 0000000000000045 x21: 05ffc00000000015
> x20: ffff0000ca7403b8 x19: fffffc00032ec600 x18: 0000000000000181
> x17: ffff80000c04d6bc x16: ffff80000dbb8658 x15: 0000000000000000
> x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
> x11: ff808000083e9814 x10: 0000000000000000 x9 : ffff8000083e9814
> x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
> x5 : ffff0000cbb19000 x4 : ffff0000cb3d2000 x3 : ffff0000cbb18f80
> x2 : fffffffffffffff0 x1 : fffffc00032ec600 x0 : ffff0000ca7403b8
> Call trace:
> 0x0
> set_page_dirty+0x38/0xbc mm/folio-compat.c:62
> f2fs_update_meta_page+0x80/0xa8 fs/f2fs/segment.c:2369
> do_checkpoint+0x794/0xea8 fs/f2fs/checkpoint.c:1522
> f2fs_write_checkpoint+0x3b8/0x568 fs/f2fs/checkpoint.c:1679
>
> The root cause is, quoted from Jaegeuk:
>
> It turned out there is a bug in reiserfs which doesn't free the root
> inode (ino=2). That leads f2fs to find an ino=2 with the previous
> superblock point used by reiserfs. That stale inode has no valid
> mapping that f2fs can use, result in kernel panic.
>
> This patch adds sanity check in f2fs_iget() to avoid finding stale
> inode during inner inode initialization.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Reported-by: syzbot+775a3440817f74fddb8c@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> Signed-off-by: Chao Yu <chao@xxxxxxxxxx>
> ---
> fs/f2fs/inode.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
> index ccb29034af59..df1a82fbfaf2 100644
> --- a/fs/f2fs/inode.c
> +++ b/fs/f2fs/inode.c
> @@ -493,6 +493,17 @@ struct inode *f2fs_iget_inner(struct super_block *sb, unsigned long ino)
> struct inode *inode;
> int ret = 0;
>
> + if (ino == F2FS_NODE_INO(sbi) || ino == F2FS_META_INO(sbi) ||
> + ino == F2FS_COMPRESS_INO(sbi)) {
> + inode = ilookup(sb, ino);
> + if (inode) {
> + iput(inode);
> + f2fs_err(sbi, "there is obsoleted inner inode %lu cached in hash table",
> + ino);
> + return ERR_PTR(-EFSCORRUPTED);
Well, this does not indicate f2fs is corrupted. I'd rather expect to fix
reiserfs instead of f2fs workaround which hides the bug.
> + }
> + }
> +
> inode = iget_locked(sb, ino);
> if (!inode)
> return ERR_PTR(-ENOMEM);
> --
> 2.25.1
