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>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 3555e72..c713d06 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -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);