[PATCH] libext2fs: ensure validate_entry doesn't read beyond blocksize

[PATCH] libext2fs: ensure validate_entry doesn't read beyond blocksize

[number9652]

ext2fs_validate_entry would read beyond the end of the block to get dirent->rec_len for certain arguments (like if blocksize == final_offset).  This patch adds a check so that doesn't happen, and changes the types of the arguments to avoid a compiler warning.

Signed-off-by: Nic Case <number9652@yahoo.com>

diff --git a/e2fsprogs-1.41.5-orig/lib/ext2fs/dir_iterate.c b/e2fsprogs-1.41.5/lib/ext2fs/dir_iterate.c
index 1f8cf8f..6be066c 100644
--- a/e2fsprogs-1.41.5-orig/lib/ext2fs/dir_iterate.c
+++ b/e2fsprogs-1.41.5/lib/ext2fs/dir_iterate.c
@@ -29,13 +29,15 @@
  * undeleted entry.  Returns 1 if the deleted entry looks valid, zero
  * if not valid.
  */
-static int ext2fs_validate_entry(ext2_filsys fs, char *buf, int offset,
-				 int final_offset)
+static int ext2fs_validate_entry(ext2_filsys fs, char *buf,
+				 unsigned int offset,
+				 unsigned int final_offset)
 {
 	struct ext2_dir_entry *dirent;
 	int	rec_len;
+	int dirent_min_len = 12;
 
-	while (offset < final_offset) {
+	while (offset < final_offset &&	offset <= fs->blocksize - dirent_min_len) {
 		dirent = (struct ext2_dir_entry *)(buf + offset);
 		rec_len = (dirent->rec_len || fs->blocksize < 65536) ?
 			dirent->rec_len : 65536;



      

Re: [PATCH] libext2fs: ensure validate_entry doesn't read beyond blocksize

[Theodore Tso]

On Fri, Jun 12, 2009 at 09:04:32AM -0700, number9652 wrote:
> 
> ext2fs_validate_entry would read beyond the end of the block to get dirent->rec_len for certain arguments (like if blocksize == final_offset).  This patch adds a check so that doesn't happen, and changes the types of the arguments to avoid a compiler warning.
> 
> Signed-off-by: Nic Case <number9652@yahoo.com>

Applied.  In the future, please line-wrap the body of the commit
message at 72-75 characters.

I also lined up the arguments to ext2fs_validate_entry on the
continuation line, and used a CPP macro instead of an automatic
variable for dirent_min_length.

					- Ted