From: Leo Stone leocstone@gmail.com
[ Upstream commit b905bafdea21a75d75a96855edd9e0b6051eee30 ]
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: syzbot+2db3c7526ba68f4ea776@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=2db3c7526ba68f4ea776 Tested-by: syzbot+2db3c7526ba68f4ea776@syzkaller.appspotmail.com Tested-by: Leo Stone leocstone@gmail.com Signed-off-by: Leo Stone leocstone@gmail.com Link: https://lore.kernel.org/r/20241201051420.77858-1-leocstone@gmail.com Reviewed-by: Jan Kara jack@suse.cz Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/hfs/super.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/hfs/super.c b/fs/hfs/super.c index eeac99765f0d..cf13b5cc1084 100644 --- a/fs/hfs/super.c +++ b/fs/hfs/super.c @@ -419,11 +419,13 @@ static int hfs_fill_super(struct super_block *sb, void *data, int silent) 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;