reiserfs: check directory items on read from disk

[ Upstream commit 13d257503c0930010ef9eed78b689cec417ab741 ]

While verifying the leaf item that we read from the disk, reiserfs
doesn't check the directory items, this could cause a crash when we
read a directory item from the disk that has an invalid deh_location.

This patch adds a check to the directory items read from the disk that
does a bounds check on deh_location for the directory entries. Any
directory entry header with a directory entry offset greater than the
item length is considered invalid.

Link: https://lore.kernel.org/r/20210709152929.766363-1-chouhan.shreyansh630@gmail.com
Reported-by: syzbot+c31a48e6702ccb3d64c9@syzkaller.appspotmail.com
Signed-off-by: Shreyansh Chouhan <chouhan.shreyansh630@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/reiserfs/stree.c b/fs/reiserfs/stree.c
index 25b2aed9af0b3394deaa1f03cfcc4f1275fb8e18..f2f7055303ca528b4213132e6746177ed11b7098 100644 (file)
--- a/fs/reiserfs/stree.c
+++ b/fs/reiserfs/stree.c
@@ -386,6 +386,24 @@ void pathrelse(struct treepath *search_path)
        search_path->path_length = ILLEGAL_PATH_ELEMENT_OFFSET;
 }
 
+static int has_valid_deh_location(struct buffer_head *bh, struct item_head *ih)
+{
+       struct reiserfs_de_head *deh;
+       int i;
+
+       deh = B_I_DEH(bh, ih);
+       for (i = 0; i < ih_entry_count(ih); i++) {
+               if (deh_location(&deh[i]) > ih_item_len(ih)) {
+                       reiserfs_warning(NULL, "reiserfs-5094",
+                                        "directory entry location seems wrong %h",
+                                        &deh[i]);
+                       return 0;
+               }
+       }
+
+       return 1;
+}
+
 static int is_leaf(char *buf, int blocksize, struct buffer_head *bh)
 {
        struct block_head *blkh;
@@ -453,11 +471,14 @@ static int is_leaf(char *buf, int blocksize, struct buffer_head *bh)
                                         "(second one): %h", ih);
                        return 0;
                }
-               if (is_direntry_le_ih(ih) && (ih_item_len(ih) < (ih_entry_count(ih) * IH_SIZE))) {
-                       reiserfs_warning(NULL, "reiserfs-5093",
-                                        "item entry count seems wrong %h",
-                                        ih);
-                       return 0;
+               if (is_direntry_le_ih(ih)) {
+                       if (ih_item_len(ih) < (ih_entry_count(ih) * IH_SIZE)) {
+                               reiserfs_warning(NULL, "reiserfs-5093",
+                                                "item entry count seems wrong %h",
+                                                ih);
+                               return 0;
+                       }
+                       return has_valid_deh_location(bh, ih);
                }
                prev_location = ih_location(ih);
        }