On Mon, Aug 19, 2024 at 08:31:26PM +0800, Kemeng Shi wrote:
>
>
> on 8/16/2024 3:57 PM, Ojaswin Mujoo wrote:
> > We disable stripe size in __ext4_fill_super if it is not a multiple of
> > the cluster ratio however this check is missed when trying to remount.
> > This can leave us with cases where stripe < cluster_ratio after
> > remount:set making EXT4_B2C(sbi->s_stripe) become 0 that can cause some
> > unforeseen bugs like divide by 0.
> >
> > Fix that by adding the check in remount path as well.
> >
> > Additionally, change the users of EXT4_B2C(sbi->s_stripe) to
> > EXT4_NUM_B2C() so that if we ever accidentally hit this again, we can
> > avoid the value becoming 0. This should not change existing functionality.
> It's better to mention this change is in following patch or simply remove
> it from this patch.
Oh yes you are right, I accidentally left it here. I'll fix it.
>
> Other than that, looks good to me. Feel free to add:
>
> Reviewed-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
Thanks for the review!
Regards,
Ojaswin
> >
> > Reported-by: syzbot+1ad8bac5af24d01e2cbd@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Tested-by: syzbot+1ad8bac5af24d01e2cbd@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Fixes: c3defd99d58c ("ext4: treat stripe in block unit")
> > Signed-off-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>
> > ---
> > fs/ext4/super.c | 29 ++++++++++++++++++++++-------
> > 1 file changed, 22 insertions(+), 7 deletions(-)
> >
> > diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> > index e72145c4ae5a..9d495d78d262 100644
> > --- a/fs/ext4/super.c
> > +++ b/fs/ext4/super.c
> > @@ -5165,6 +5165,18 @@ static int ext4_block_group_meta_init(struct super_block *sb, int silent)
> > return 0;
> > }
> >
> > +/*
> > + * It's hard to get stripe aligned blocks if stripe is not aligned with
> > + * cluster, just disable stripe and alert user to simpfy code and avoid
> > + * stripe aligned allocation which will rarely successes.
> > + */
> > +static bool ext4_is_stripe_incompatible(struct super_block *sb, unsigned long stripe)
> > +{
> > + struct ext4_sb_info *sbi = EXT4_SB(sb);
> > + return (stripe > 0 && sbi->s_cluster_ratio > 1 &&
> > + stripe % sbi->s_cluster_ratio != 0);
> > +}
> > +
> > static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
> > {
> > struct ext4_super_block *es = NULL;
> > @@ -5272,13 +5284,7 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
> > goto failed_mount3;
> >
> > sbi->s_stripe = ext4_get_stripe_size(sbi);
> > - /*
> > - * It's hard to get stripe aligned blocks if stripe is not aligned with
> > - * cluster, just disable stripe and alert user to simpfy code and avoid
> > - * stripe aligned allocation which will rarely successes.
> > - */
> > - if (sbi->s_stripe > 0 && sbi->s_cluster_ratio > 1 &&
> > - sbi->s_stripe % sbi->s_cluster_ratio != 0) {
> > + if (ext4_is_stripe_incompatible(sb, sbi->s_stripe)) {
> > ext4_msg(sb, KERN_WARNING,
> > "stripe (%lu) is not aligned with cluster size (%u), "
> > "stripe is disabled",
> > @@ -6441,6 +6447,15 @@ static int __ext4_remount(struct fs_context *fc, struct super_block *sb)
> >
> > }
> >
> > + if ((ctx->spec & EXT4_SPEC_s_stripe) &&
> > + ext4_is_stripe_incompatible(sb, ctx->s_stripe)) {
> > + ext4_msg(sb, KERN_WARNING,
> > + "stripe (%lu) is not aligned with cluster size (%u), "
> > + "stripe is disabled",
> > + ctx->s_stripe, sbi->s_cluster_ratio);
> > + ctx->s_stripe = 0;
> > + }
> > +
> > /*
> > * Changing the DIOREAD_NOLOCK or DELALLOC mount options may cause
> > * two calls to ext4_should_dioread_nolock() to return inconsistent
> >
>
