Commit ee85e093 authored by Ojaswin Mujoo's avatar Ojaswin Mujoo Committed by Theodore Ts'o
Browse files

ext4: check stripe size compatibility on remount as well 



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.

Reported-by: default avatar <syzbot+1ad8bac5af24d01e2cbd@syzkaller.appspotmail.com>
Tested-by: default avatar <syzbot+1ad8bac5af24d01e2cbd@syzkaller.appspotmail.com>
Reviewed-by: default avatarKemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: default avatarRitesh Harjani (IBM) <ritesh.list@gmail.com>
Fixes: c3defd99 ("ext4: treat stripe in block unit")
Signed-off-by: default avatarOjaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://patch.msgid.link/3a493bb503c3598e25dcfbed2936bb2dff3fece7.1725002410.git.ojaswin@linux.ibm.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent cc749e61

fs/ext4/super.c

+22 −7
Original line number Diff line number Diff line
@@ -5178,6 +5178,18 @@ 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 simplify code and avoid

 * stripe aligned allocation which will rarely succeed.

 */

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;
@@ -5287,13 +5299,7 @@ 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",
@@ -6457,6 +6463,15 @@ 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