From: Theodore Ts'o <tytso@mit.edu>
Date: Mon, 12 Mar 2012 03:30:16 +0000 (-0400)
Subject: ext4: check for zero length extent
X-Git-Tag: firefly_0821_release~7541^2~1468
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=471320c7569290aeed04f9c730d92b67b9acb53d;p=firefly-linux-kernel-4.4.55.git

ext4: check for zero length extent

commit 31d4f3a2f3c73f279ff96a7135d7202ef6833f12 upstream.

Explicitly test for an extent whose length is zero, and flag that as a
corrupted extent.

This avoids a kernel BUG_ON assertion failure.

Tested: Without this patch, the file system image found in
tests/f_ext_zero_len/image.gz in the latest e2fsprogs sources causes a
kernel panic.  With this patch, an ext4 file system error is noted
instead, and the file system is marked as being corrupted.

https://bugzilla.kernel.org/show_bug.cgi?id=42859

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index f3aacb32059f..7fc10ed7ef45 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -341,6 +341,8 @@ static int ext4_valid_extent(struct inode *inode, struct ext4_extent *ext)
 	ext4_fsblk_t block = ext4_ext_pblock(ext);
 	int len = ext4_ext_get_actual_len(ext);
 
+	if (len == 0)
+		return 0;
 	return ext4_data_block_valid(EXT4_SB(inode->i_sb), block, len);
 }