Commit eb2b8ebb authored by Ritesh Harjani's avatar Ritesh Harjani Committed by Theodore Ts'o
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ext4: mballoc: fix possible NULL ptr & remove BUG_ONs from DOUBLE_CHECK 

Make sure to check for e4b->bd_info->bb_bitmap == NULL, in
mb_cmp_bitmaps() and return if NULL, to avoid possible NULL ptr
dereference. Similar to how we do this in other ifdef DOUBLE_CHECK
functions.

Also remove the BUG_ON() logic if kmalloc() or ext4_read_block_bitmap()
fails. We should simply mark grp->bb_bitmap as NULL if above happens.
In fact ext4_read_block_bitmap() may even return an error in case of resize
ioctl. Hence remove this BUG_ON logic (fstests ext4/032 may trigger
this).

Link: https://lore.kernel.org/r/9a54f8a696ff17c057cd571be3d15ac3ec1407f1.1589086800.git.riteshh@linux.ibm.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent a3450215

fs/ext4/mballoc.c

+9 −2
Original line number Diff line number Diff line
@@ -493,6 +493,8 @@ static void mb_mark_used_double(struct ext4_buddy *e4b, int first, int count) 


static void mb_cmp_bitmaps(struct ext4_buddy *e4b, void *bitmap)

{

	if (unlikely(e4b->bd_info->bb_bitmap == NULL))

		return;

	if (memcmp(e4b->bd_info->bb_bitmap, bitmap, e4b->bd_sb->s_blocksize)) {

		unsigned char *b1, *b2;

		int i;
@@ -517,10 +519,15 @@ static void mb_group_bb_bitmap_alloc(struct super_block *sb, 
	struct buffer_head *bh;



	grp->bb_bitmap = kmalloc(sb->s_blocksize, GFP_NOFS);

	BUG_ON(grp->bb_bitmap == NULL);

	if (!grp->bb_bitmap)

		return;



	bh = ext4_read_block_bitmap(sb, group);

	BUG_ON(IS_ERR_OR_NULL(bh));

	if (IS_ERR_OR_NULL(bh)) {

		kfree(grp->bb_bitmap);

		grp->bb_bitmap = NULL;

		return;

	}



	memcpy(grp->bb_bitmap, bh->b_data, sb->s_blocksize);

	put_bh(bh);