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ext2: skip pages past number of blocks in ext2_find_entry

PATCH In review Eric Sandeen 2 participants 4 messages Dec 21, 2006 ext2 file system

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Eric Sandeen

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#0 lore raw

PATCH 1/1 ext2: skip pages past number of blocks in ext2_find_entry

This one was pointed out on the MOKB site:
http://kernelfun.blogspot.com/2006/11/mokb-09-11-2006-linux-26x-ext2checkpage.html

If a directory's i_size is corrupted, ext2_find_entry() will keep processing pages until the i_size is reached, even if there are no more blocks associated with the directory inode. This patch puts in some minimal sanity-checking so that we don't keep checking pages (and issuing errors) if we know there can be no more data to read, based on the block count of the directory inode.

This is somewhat similar in approach to the ext3 patch I sent earlier this year.

Thanks,

-Eric

Signed-off-by Eric Sandeen <[email protected]>
fs/ext2/dir.c +8 -0
Index: linux-2.6.19/fs/ext2/dir.c
===================================================================
@@ -368,6 +368,14 @@ struct ext2_dir_entry_2 * ext2_find_entr
 		}
 		if (++n >= npages)
 			n = 0;
+		/* next page is past the blocks we've got */
+		if (unlikely(n > (dir->i_blocks >> (PAGE_CACHE_SHIFT - 9)))) {
+			ext2_error(dir->i_sb, __FUNCTION__,
+				"dir %lu size %lld exceeds block count %llu",
+				dir->i_ino, dir->i_size,
+				(unsigned long long)dir->i_blocks);
+				goto out;
+		}
 	} while (n != start);
 out:
 	return NULL;
#1 lore raw
Quoted 23 lines · On Thu, 21 Dec 2006 12:58:28 -0600 Eric Sandeen wrote:

This one was pointed out on the MOKB site:
http://kernelfun.blogspot.com/2006/11/mokb-09-11-2006-linux-26x-ext2checkpage.html

If a directory's i_size is corrupted, ext2_find_entry() will keep processing pages until the i_size is reached, even if there are no more blocks associated with the directory inode. This patch puts in some minimal sanity-checking so that we don't keep checking pages (and issuing errors) if we know there can be no more data to read, based on the block count of the directory inode.

This is somewhat similar in approach to the ext3 patch I sent earlier this year.

Thanks,

-Eric

Signed-off-by Eric Sandeen <[email protected]>

Index: linux-2.6.19/fs/ext2/dir.c
===================================================================

fs/ext2/dir.c struct ext2_dir_entry_2 * ext2_find_entr · line 377

Quoted 10 lines
fs/ext2/dir.c +7 -0
@@ -368,6 +368,14 @@ struct ext2_dir_entry_2 * ext2_find_entr
 		}
 		if (++n >= npages)
 			n = 0;
+		/* next page is past the blocks we've got */
+		if (unlikely(n > (dir->i_blocks >> (PAGE_CACHE_SHIFT - 9)))) {
+			ext2_error(dir->i_sb, __FUNCTION__,
+				"dir %lu size %lld exceeds block count %llu",
+				dir->i_ino, dir->i_size,
+				(unsigned long long)dir->i_blocks);
+				goto out;

Please don't hide the goto; un-indent 1 tab stop.

fs/ext2/dir.c struct ext2_dir_entry_2 * ext2_find_entr · line 381

Quoted 4 lines
fs/ext2/dir.c +1 -0
+		}
 	} while (n != start);
 out:
 	return NULL;

---
~Randy

author
#2 lore raw
Quoted 1 line · Randy Dunlap

Please don't hide the goto; un-indent 1 tab stop.

Whoops, thanks Randy - it wasn't intentional. :)

Signed-off-by Eric Sandeen <[email protected]>
fs/ext2/dir.c +8 -0
Index: linux-2.6.19/fs/ext2/dir.c
===================================================================
@@ -368,6 +368,14 @@ struct ext2_dir_entry_2 * ext2_find_entr
 		}
 		if (++n >= npages)
 			n = 0;
+		/* next page is past the blocks we've got */
+		if (unlikely(n > (dir->i_blocks >> (PAGE_CACHE_SHIFT - 9)))) {
+			ext2_error(dir->i_sb, __FUNCTION__,
+				"dir %lu size %lld exceeds block count %llu",
+				dir->i_ino, dir->i_size,
+				(unsigned long long)dir->i_blocks);
+			goto out;
+		}
 	} while (n != start);
 out:
 	return NULL;
#3 lore raw
Quoted 4 lines · On Thu, 21 Dec 2006 13:11:01 -0600 Eric Sandeen wrote:
Quoted 1 line · Randy Dunlap

Please don't hide the goto; un-indent 1 tab stop.

Whoops, thanks Randy - it wasn't intentional. :)

Yeah, I didn't think it was. Sorry if it sounded like that.

---
~Randy