Commit eb2b8ebb authored May 10, 2020 by Ritesh Harjani Committed by Theodore Ts'o Jun 03, 2020

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: Theodore 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);

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