linux-ext4 - [PATCH 03/39] libext2fs: directory iteration mustn't walk off the buffer end

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Message-ID: <20141025205642.532.35826.stgit@birch.djwong.org>
Date:	Sat, 25 Oct 2014 13:56:42 -0700
From:	"Darrick J. Wong" <darrick.wong@...cle.com>
To:	tytso@....edu, darrick.wong@...cle.com
Cc:	Sami Liedes <sami.liedes@....fi>, linux-ext4@...r.kernel.org
Subject: [PATCH 03/39] libext2fs: directory iteration mustn't walk off the
 buffer end

When we're iterating a directory, the loop control code reads the
length of the next directory record, failing to account for the fact
that there must be at least 8 bytes (the minimum size of a directory
entry) left in the buffer to read the next directory record.  Fix the
loop conditional so that we don't read off the end of the buffer.

Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
Reported-by: Sami Liedes <sami.liedes@....fi>
---
 lib/ext2fs/dir_iterate.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/ext2fs/dir_iterate.c b/lib/ext2fs/dir_iterate.c
index 67152cc..9063c17 100644
--- a/lib/ext2fs/dir_iterate.c
+++ b/lib/ext2fs/dir_iterate.c
@@ -222,7 +222,7 @@ int ext2fs_process_dir_block(ext2_filsys fs,
 					EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
 		csum_size = sizeof(struct ext2_dir_entry_tail);

-	while (offset < buflen) {
+	while (offset < buflen - 8) {
 		dirent = (struct ext2_dir_entry *) (ctx->buf + offset);
 		if (ext2fs_get_rec_len(fs, dirent, &rec_len))
 			return BLOCK_ABORT;

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