Unverified Commit b905bafd authored by Leo Stone's avatar Leo Stone Committed by Christian Brauner
Browse files

hfs: Sanity check the root record 



In the syzbot reproducer, the hfs_cat_rec for the root dir has type
HFS_CDR_FIL after being read with hfs_bnode_read() in hfs_super_fill().
This indicates it should be used as an hfs_cat_file, which is 102 bytes.
Only the first 70 bytes of that struct are initialized, however,
because the entrylength passed into hfs_bnode_read() is still the length of
a directory record. This causes uninitialized values to be used later on,
when the hfs_cat_rec union is treated as the larger hfs_cat_file struct.

Add a check to make sure the retrieved record has the correct type
for the root directory (HFS_CDR_DIR), and make sure we load the correct
number of bytes for a directory record.

Reported-by: default avatar <syzbot+2db3c7526ba68f4ea776@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=2db3c7526ba68f4ea776


Tested-by: default avatar <syzbot+2db3c7526ba68f4ea776@syzkaller.appspotmail.com>
Tested-by: default avatarLeo Stone <leocstone@gmail.com>
Signed-off-by: default avatarLeo Stone <leocstone@gmail.com>
Link: https://lore.kernel.org/r/20241201051420.77858-1-leocstone@gmail.com


Reviewed-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 40384c84

fs/hfs/super.c

+3 −1
Original line number Diff line number Diff line
@@ -349,11 +349,13 @@ static int hfs_fill_super(struct super_block *sb, struct fs_context *fc) 
		goto bail_no_root;

	res = hfs_cat_find_brec(sb, HFS_ROOT_CNID, &fd);

	if (!res) {

		if (fd.entrylength > sizeof(rec) || fd.entrylength < 0) {

		if (fd.entrylength != sizeof(rec.dir)) {

			res =  -EIO;

			goto bail_hfs_find;

		}

		hfs_bnode_read(fd.bnode, &rec, fd.entryoffset, fd.entrylength);

		if (rec.type != HFS_CDR_DIR)

			res = -EIO;

	}

	if (res)

		goto bail_hfs_find;