linux-kernel - [PATCH] reiserfs: add check for an invalid ih_entry

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Message-Id: <20201101140958.3650143-1-rkovhaev@gmail.com>
Date:   Sun,  1 Nov 2020 06:09:58 -0800
From:   Rustam Kovhaev <rkovhaev@...il.com>
To:     alex.shi@...ux.alibaba.com, jack@...e.cz,
        akpm@...ux-foundation.org, yeyunfeng@...wei.com
Cc:     reiserfs-devel@...r.kernel.org, linux-kernel@...r.kernel.org,
        gregkh@...uxfoundation.org, Rustam Kovhaev <rkovhaev@...il.com>
Subject: [PATCH] reiserfs: add check for an invalid ih_entry_count

when directory item has an invalid value set for ih_entry_count it might
trigger use-after-free or out-of-bounds read in bin_search_in_dir_item()

ih_entry_count * IH_SIZE for directory item should not be larger than
ih_item_len

Reported-and-tested-by: syzbot+83b6f7cf9922cae5c4d7@...kaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=83b6f7cf9922cae5c4d7
Signed-off-by: Rustam Kovhaev <rkovhaev@...il.com>
---
 fs/reiserfs/stree.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/reiserfs/stree.c b/fs/reiserfs/stree.c
index 8bf88d690729..476a7ff49482 100644
--- a/fs/reiserfs/stree.c
+++ b/fs/reiserfs/stree.c
@@ -454,6 +454,12 @@ 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;
+		}
 		prev_location = ih_location(ih);
 	}
 
-- 
2.28.0