On Thu, Oct 12, 2017 at 02:16:10AM -0400, Nicolas Pitre wrote:
> static void cramfs_kill_sb(struct super_block *sb)
> {
> struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
>
> - kill_block_super(sb);
> + if (IS_ENABLED(CCONFIG_CRAMFS_MTD)) {
> + if (sbi->mtd_point_size)
> + mtd_unpoint(sb->s_mtd, 0, sbi->mtd_point_size);
> + if (sb->s_mtd)
> + kill_mtd_super(sb);
...
> + mtd_unpoint(sb->s_mtd, 0, PAGE_SIZE);
> + err = mtd_point(sb->s_mtd, 0, sbi->size, &sbi->mtd_point_size,
> + &sbi->linear_virt_addr, &sbi->linear_phys_addr);
> + if (err || sbi->mtd_point_size != sbi->size) {
What happens if that mtd_point() fails? Note that ->kill_sb() will be
called anyway and ->mtd_point_size is going to be non-zero here... Do
we get the second mtd_unpoint(), or am I misreading that code?
This logics does look fishy, but I'm not familiar enough with mtd guts
to tell if that's OK...
Rules regarding ->kill_sb(): any struct super_block instance that
got out of sget() and its ilk will have ->kill_sb() called. In case of
mtd, it's simply "if that thing got past setting ->s_mtd, it will be
passed to ->kill_sb()".
Note, BTW, that you *must* have generic_shutdown_super() called once on
every reachable path in ->kill_sb(). AFAICS your patch is correct in
that area (all instances with that ->s_type are created either in
mount_bdev() or in mount_mtd(); the former will have non-NULL ->s_bdev,
the latter - non-NULL ->s_mtd), but that's one thing to watch out when
doing any modifications.
