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udf: Avoid using corrupted block bitmap buffer 

[ Upstream commit a90d4471146de21745980cba51ce88e7926bcc4f ]

Fix CVE: CVE-2024-42306

When the filesystem block bitmap is corrupted, we detect the corruption
while loading the bitmap and fail the allocation with error. However the
next allocation from the same bitmap will notice the bitmap buffer is
already loaded and tries to allocate from the bitmap with mixed results
(depending on the exact nature of the bitmap corruption). Fix the
problem by using BH_verified bit to indicate whether the bitmap is valid
or not.

Reported-by: syzbot+5f682cd029581f9edfd1@syzkaller.appspotmail.com
CC: stable@vger.kernel.org
Link: https://patch.msgid.link/20240617154201.29512-2-jack@suse.cz
Fixes: 1e0d4adf17 ("udf: Check consistency of Space Bitmap Descriptor")
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Haisu Wang <haisuwang@tencent.com>
Signed-off-by: Jianping Liu <frankjpliu@tencent.com>
This commit is contained in:
Jan Kara 2024-06-17 17:41:52 +02:00 committed by Jianping Liu
parent 2d804bc89c
commit 3960a1c18c
2 changed files with 15 additions and 3 deletions
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15
fs/udf/balloc.c
View File

@ -68,8 +68,12 @@ static int read_block_bitmap(struct super_block *sb,
}
for (i = 0; i < count; i++)
if (udf_test_bit(i + off, bh->b_data))
if (udf_test_bit(i + off, bh->b_data)) {
bitmap->s_block_bitmap[bitmap_nr] =
ERR_PTR(-EFSCORRUPTED);
brelse(bh);
return -EFSCORRUPTED;
}
return 0;
}
@ -85,8 +89,15 @@ static int __load_block_bitmap(struct super_block *sb,
block_group, nr_groups);
}
if (bitmap->s_block_bitmap[block_group])
if (bitmap->s_block_bitmap[block_group]) {
/*
* The bitmap failed verification in the past. No point in
* trying again.
*/
if (IS_ERR(bitmap->s_block_bitmap[block_group]))
return PTR_ERR(bitmap->s_block_bitmap[block_group]);
return block_group;
}
retval = read_block_bitmap(sb, bitmap, block_group, block_group);
if (retval < 0)

3
fs/udf/super.c
View File

@ -266,7 +266,8 @@ static void udf_sb_free_bitmap(struct udf_bitmap *bitmap)
int nr_groups = bitmap->s_nr_groups;
for (i = 0; i < nr_groups; i++)
brelse(bitmap->s_block_bitmap[i]);
if (!IS_ERR_OR_NULL(bitmap->s_block_bitmap[i]))
brelse(bitmap->s_block_bitmap[i]);
kvfree(bitmap);
}