ext[234]: Avoid printk floods in the face of directory corruption (CVE-2008-3528)

This is a trivial backport of the following upstream commits:

- bd39597cbd42a784105a04010100e27267481c67 (ext2)
- cdbf6dba28e8e6268c8420857696309470009fd9 (ext3)
- 9d9f177572d9e4eba0f2e18523b44f90dd51fe74 (ext4)

This addresses CVE-2008-3528

ext[234]: Avoid printk floods in the face of directory corruption

Note: some people thinks this represents a security bug, since it
might make the system go away while it is printing a large number of
console messages, especially if a serial console is involved.  Hence,
it has been assigned CVE-2008-3528, but it requires that the attacker
either has physical access to your machine to insert a USB disk with a
corrupted filesystem image (at which point why not just hit the power
button), or is otherwise able to convince the system administrator to
mount an arbitrary filesystem image (at which point why not just
include a setuid shell or world-writable hard disk device file or some
such).  Me, I think they're just being silly. --tytso

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: linux-ext4@vger.kernel.org
Cc: Eugene Teo <eugeneteo@kernel.sg>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 50 insertions, 31 deletions

diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
index a78c6b4af060..11a49ce84392 100644
--- a/fs/ext2/dir.c
+++ b/fs/ext2/dir.c
@@ -103,7 +103,7 @@ static int ext2_commit_chunk(struct page *page, loff_t pos, unsigned len)
 	return err;
 }
 
-static void ext2_check_page(struct page *page)
+static void ext2_check_page(struct page *page, int quiet)
 {
 	struct inode *dir = page->mapping->host;
 	struct super_block *sb = dir->i_sb;
@@ -146,10 +146,10 @@ out:
 	/* Too bad, we had an error */
 
 Ebadsize:
-	ext2_error(sb, "ext2_check_page",
-		"size of directory #%lu is not a multiple of chunk size",
-		dir->i_ino
-	);
+	if (!quiet)
+		ext2_error(sb, __func__,
+			"size of directory #%lu is not a multiple "
+			"of chunk size", dir->i_ino);
 	goto fail;
 Eshort:
 	error = "rec_len is smaller than minimal";
@@ -166,32 +166,36 @@ Espan:
 Einumber:
 	error = "inode out of bounds";
 bad_entry:
-	ext2_error (sb, "ext2_check_page", "bad entry in directory #%lu: %s - "
-		"offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
-		dir->i_ino, error, (page->index<<PAGE_CACHE_SHIFT)+offs,
-		(unsigned long) le32_to_cpu(p->inode),
-		rec_len, p->name_len);
+	if (!quiet)
+		ext2_error(sb, __func__, "bad entry in directory #%lu: : %s - "
+			"offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
+			dir->i_ino, error, (page->index<<PAGE_CACHE_SHIFT)+offs,
+			(unsigned long) le32_to_cpu(p->inode),
+			rec_len, p->name_len);
 	goto fail;
 Eend:
-	p = (ext2_dirent *)(kaddr + offs);
-	ext2_error (sb, "ext2_check_page",
-		"entry in directory #%lu spans the page boundary"
-		"offset=%lu, inode=%lu",
-		dir->i_ino, (page->index<<PAGE_CACHE_SHIFT)+offs,
-		(unsigned long) le32_to_cpu(p->inode));
+	if (!quiet) {
+		p = (ext2_dirent *)(kaddr + offs);
+		ext2_error(sb, "ext2_check_page",
+			"entry in directory #%lu spans the page boundary"
+			"offset=%lu, inode=%lu",
+			dir->i_ino, (page->index<<PAGE_CACHE_SHIFT)+offs,
+			(unsigned long) le32_to_cpu(p->inode));
+	}
 fail:
 	SetPageChecked(page);
 	SetPageError(page);
 }
 
-static struct page * ext2_get_page(struct inode *dir, unsigned long n)
+static struct page * ext2_get_page(struct inode *dir, unsigned long n,
+				   int quiet)
 {
 	struct address_space *mapping = dir->i_mapping;
 	struct page *page = read_mapping_page(mapping, n, NULL);
 	if (!IS_ERR(page)) {
 		kmap(page);
 		if (!PageChecked(page))
-			ext2_check_page(page);
+			ext2_check_page(page, quiet);
 		if (PageError(page))
 			goto fail;
 	}
@@ -292,7 +296,7 @@ ext2_readdir (struct file * filp, void * dirent, filldir_t filldir)
 	for ( ; n < npages; n++, offset = 0) {
 		char *kaddr, *limit;
 		ext2_dirent *de;
-		struct page *page = ext2_get_page(inode, n);
+		struct page *page = ext2_get_page(inode, n, 0);
 
 		if (IS_ERR(page)) {
 			ext2_error(sb, __func__,
@@ -361,6 +365,7 @@ struct ext2_dir_entry_2 * ext2_find_entry (struct inode * dir,
 	struct page *page = NULL;
 	struct ext2_inode_info *ei = EXT2_I(dir);
 	ext2_dirent * de;
+	int dir_has_error = 0;
 
 	if (npages == 0)
 		goto out;
@@ -374,7 +379,7 @@ struct ext2_dir_entry_2 * ext2_find_entry (struct inode * dir,
 	n = start;
 	do {
 		char *kaddr;
-		page = ext2_get_page(dir, n);
+		page = ext2_get_page(dir, n, dir_has_error);
 		if (!IS_ERR(page)) {
 			kaddr = page_address(page);
 			de = (ext2_dirent *) kaddr;
@@ -391,7 +396,9 @@ struct ext2_dir_entry_2 * ext2_find_entry (struct inode * dir,
 				de = ext2_next_entry(de);
 			}
 			ext2_put_page(page);
-		}
+		} else
+			dir_has_error = 1;
+
 		if (++n >= npages)
 			n = 0;
 		/* next page is past the blocks we've got */
@@ -414,7 +421,7 @@ found:
 
 struct ext2_dir_entry_2 * ext2_dotdot (struct inode *dir, struct page **p)
 {
-	struct page *page = ext2_get_page(dir, 0);
+	struct page *page = ext2_get_page(dir, 0, 0);
 	ext2_dirent *de = NULL;
 
 	if (!IS_ERR(page)) {
@@ -487,7 +494,7 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode)
 	for (n = 0; n <= npages; n++) {
 		char *dir_end;
 
-		page = ext2_get_page(dir, n);
+		page = ext2_get_page(dir, n, 0);
 		err = PTR_ERR(page);
 		if (IS_ERR(page))
 			goto out;
@@ -655,14 +662,17 @@ int ext2_empty_dir (struct inode * inode)
 {
 	struct page *page = NULL;
 	unsigned long i, npages = dir_pages(inode);
+	int dir_has_error = 0;
 
 	for (i = 0; i < npages; i++) {
 		char *kaddr;
 		ext2_dirent * de;
-		page = ext2_get_page(inode, i);
+		page = ext2_get_page(inode, i, dir_has_error);
 
-		if (IS_ERR(page))
+		if (IS_ERR(page)) {
+			dir_has_error = 1;
 			continue;
+		}
 
 		kaddr = page_address(page);
 		de = (ext2_dirent *)kaddr;
diff --git a/fs/ext3/dir.c b/fs/ext3/dir.c
index 2eea96ec78ed..1b80f1c2d96e 100644
--- a/fs/ext3/dir.c
+++ b/fs/ext3/dir.c
@@ -102,6 +102,7 @@ static int ext3_readdir(struct file * filp,
 	int err;
 	struct inode *inode = filp->f_path.dentry->d_inode;
 	int ret = 0;
+	int dir_has_error = 0;
 
 	sb = inode->i_sb;
 
@@ -148,9 +149,12 @@ static int ext3_readdir(struct file * filp,
 		 * of recovering data when there's a bad sector
 		 */
 		if (!bh) {
-			ext3_error (sb, "ext3_readdir",
-				"directory #%lu contains a hole at offset %lu",
-				inode->i_ino, (unsigned long)filp->f_pos);
+			if (!dir_has_error) {
+				ext3_error(sb, __func__, "directory #%lu "
+					"contains a hole at offset %lld",
+					inode->i_ino, filp->f_pos);
+				dir_has_error = 1;
+			}
 			/* corrupt size?  Maybe no more blocks to read */
 			if (filp->f_pos > inode->i_blocks << 9)
 				break;
diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index ec8e33b45219..d1d648790fc6 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -102,6 +102,7 @@ static int ext4_readdir(struct file * filp,
 	int err;
 	struct inode *inode = filp->f_path.dentry->d_inode;
 	int ret = 0;
+	int dir_has_error = 0;
 
 	sb = inode->i_sb;
 
@@ -148,9 +149,13 @@ static int ext4_readdir(struct file * filp,
 		 * of recovering data when there's a bad sector
 		 */
 		if (!bh) {
-			ext4_error (sb, "ext4_readdir",
-				"directory #%lu contains a hole at offset %lu",
-				inode->i_ino, (unsigned long)filp->f_pos);
+			if (!dir_has_error) {
+				ext4_error(sb, __func__, "directory #%lu "
+					   "contains a hole at offset %Lu",
+					   inode->i_ino,
+					   (unsigned long long) filp->f_pos);
+				dir_has_error = 1;
+			}
 			/* corrupt size?  Maybe no more blocks to read */
 			if (filp->f_pos > inode->i_blocks << 9)
 				break;