2012-03-11 20:46:34

by Theodore Ts'o

Subject: [PATCH] ext4: check for zero length extent

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 systmem 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" <[email protected]>
---
fs/ext4/extents.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 74f23c2..203885c 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -300,6 +300,8 @@ 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)
+ return 0;
return ext4_data_block_valid(EXT4_SB(inode->i_sb), block, len);
}

--
1.7.9.107.g97f9a

2012-03-12 02:00:27

by Andreas Dilger

Subject: Re: [PATCH] ext4: check for zero length extent

On 2012-03-11, at 14:46, Theodore Ts'o <[email protected]> wrote:
> Explicitly test for an extent whose length is zero, and flag that as a
> corrupted extent.

Two minor nits in the patch:

> 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 systmem error is noted

(typo) s/systmem/system/

> 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" <[email protected]>
> ---
> fs/ext4/extents.c | 2 ++
> 1 files changed, 2 insertions(+), 0 deletions(-)
>
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 74f23c2..203885c 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -300,6 +300,8 @@ 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)

I'd prefer:

if (len == 0)

Since len is not a Boolean.

> + return 0;
> return ext4_data_block_valid(EXT4_SB(inode->i_sb), block, len);
> }
>
> --
> 1.7.9.107.g97f9a
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html

2012-03-12 03:30:59

by Theodore Ts'o

Subject: Re: [PATCH] ext4: check for zero length extent

On Sun, Mar 11, 2012 at 08:00:58PM -0600, Andreas Dilger wrote:
> On 2012-03-11, at 14:46, Theodore Ts'o <[email protected]> wrote:
> > Explicitly test for an extent whose length is zero, and flag that as a
> > corrupted extent.
>
> Two minor nits in the patch...

Thanks, I've made your suggested fixes.

- Ted