linux-kernel - [ 140/175] ext4: check for zero length extent

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Message-Id: <20120330194854.501801795@linuxfoundation.org>
Date:	Fri, 30 Mar 2012 12:50:45 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, "Theodore Tso" <tytso@....edu>
Subject: [ 140/175] ext4: check for zero length extent

3.3-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Theodore Ts'o <tytso@....edu>

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@....edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/ext4/extents.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -300,6 +300,8 @@ static int ext4_valid_extent(struct inod
 	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);
 }
 


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