linux-kernel - [PATCH AUTOSEL 4.9 2/4] reiserfs: check directory items on read from disk

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Message-Id: <20210803114445.2253179-2-sashal@kernel.org>
Date:   Tue,  3 Aug 2021 07:44:42 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Shreyansh Chouhan <chouhan.shreyansh630@...il.com>,
        syzbot+c31a48e6702ccb3d64c9@...kaller.appspotmail.com,
        Jan Kara <jack@...e.cz>, Sasha Levin <sashal@...nel.org>,
        reiserfs-devel@...r.kernel.org
Subject: [PATCH AUTOSEL 4.9 2/4] reiserfs: check directory items on read from disk

From: Shreyansh Chouhan <chouhan.shreyansh630@...il.com>

[ 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@...kaller.appspotmail.com
Signed-off-by: Shreyansh Chouhan <chouhan.shreyansh630@...il.com>
Signed-off-by: Jan Kara <jack@...e.cz>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/reiserfs/stree.c | 31 ++++++++++++++++++++++++++-----
 1 file changed, 26 insertions(+), 5 deletions(-)

diff --git a/fs/reiserfs/stree.c b/fs/reiserfs/stree.c
index 25b2aed9af0b..f2f7055303ca 100644
--- 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);
 	}
-- 
2.30.2