Patchwork [1/2] jbd/jbd2: validate sb->s_first in journal_get_superblock()

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Submitter Eryu Guan
Date Nov. 1, 2011, 2:05 a.m.
Message ID <1320113103-27406-1-git-send-email-guaneryu@gmail.com>
Download mbox | patch
Permalink /patch/123007/
State Accepted
Headers show

Comments

Eryu Guan - Nov. 1, 2011, 2:05 a.m.
I hit a J_ASSERT(blocknr != 0) failure in cleanup_journal_tail() when
mounting a fsfuzzed ext3 image. It turns out that the corrupted ext3
image has s_first = 0 in journal superblock, and the 0 is passed to
journal->j_head in journal_reset(), then to blocknr in
cleanup_journal_tail(), in the end the J_ASSERT failed.

So validate s_first after reading journal superblock from disk in
journal_get_superblock() to ensure s_first is valid.

The following script could reproduce it:

fstype=ext3
blocksize=1024
img=$fstype.img
offset=0
found=0
magic="c0 3b 39 98"

dd if=/dev/zero of=$img bs=1M count=8
mkfs -t $fstype -b $blocksize -F $img
filesize=`stat -c %s $img`
while [ $offset -lt $filesize ]
do
        if od -j $offset -N 4 -t x1 $img | grep -i "$magic";then
                echo "Found journal: $offset"
                found=1
                break
        fi
        offset=`echo "$offset+$blocksize" | bc`
done

if [ $found -ne 1 ];then
        echo "Magic \"$magic\" not found"
        exit 1
fi

dd if=/dev/zero of=$img seek=$(($offset+23)) conv=notrunc bs=1 count=1

mkdir -p ./mnt
mount -o loop $img ./mnt

Cc: Jan Kara <jack@suse.cz>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
---
 fs/jbd/journal.c  |    8 ++++++++
 fs/jbd2/journal.c |    8 ++++++++
 2 files changed, 16 insertions(+), 0 deletions(-)
Andreas Dilger - Nov. 1, 2011, 6:55 a.m.
On 2011-10-31, at 8:05 PM, Eryu Guan wrote:
> I hit a J_ASSERT(blocknr != 0) failure in cleanup_journal_tail() when
> mounting a fsfuzzed ext3 image. It turns out that the corrupted ext3
> image has s_first = 0 in journal superblock, and the 0 is passed to
> journal->j_head in journal_reset(), then to blocknr in
> cleanup_journal_tail(), in the end the J_ASSERT failed.
> 
> So validate s_first after reading journal superblock from disk in
> journal_get_superblock() to ensure s_first is valid.
> 
> The following script could reproduce it:
> 
> fstype=ext3
> blocksize=1024
> img=$fstype.img
> offset=0
> found=0
> magic="c0 3b 39 98"
> 
> dd if=/dev/zero of=$img bs=1M count=8
> mkfs -t $fstype -b $blocksize -F $img
> filesize=`stat -c %s $img`
> while [ $offset -lt $filesize ]
> do
>        if od -j $offset -N 4 -t x1 $img | grep -i "$magic";then
>                echo "Found journal: $offset"
>                found=1
>                break
>        fi
>        offset=`echo "$offset+$blocksize" | bc`
> done
> 
> if [ $found -ne 1 ];then
>        echo "Magic \"$magic\" not found"
>        exit 1
> fi
> 
> dd if=/dev/zero of=$img seek=$(($offset+23)) conv=notrunc bs=1 count=1
> 
> mkdir -p ./mnt
> mount -o loop $img ./mnt
> 
> Cc: Jan Kara <jack@suse.cz>
> Cc: "Theodore Ts'o" <tytso@mit.edu>
> Signed-off-by: Eryu Guan <guaneryu@gmail.com>
> ---
> fs/jbd/journal.c  |    8 ++++++++
> fs/jbd2/journal.c |    8 ++++++++
> 2 files changed, 16 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c
> index 9fe061f..0c401de 100644
> --- a/fs/jbd/journal.c
> +++ b/fs/jbd/journal.c
> @@ -1135,6 +1135,14 @@ static int journal_get_superblock(journal_t *journal)
> 		goto out;
> 	}
> 
> +	if (be32_to_cpu(sb->s_first) == 0 ||
> +		be32_to_cpu(sb->s_first) >= journal->j_maxlen) {

(style) Please fix the indenting to align with '(' on previous line.

> +		printk(KERN_WARNING
> +			"JBD: Invalid start block of journal: %u\n",
> +			be32_to_cpu(sb->s_first));
> +		goto out;
> +	}
> +
> 	return 0;
> 
> out:
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index f24df13..e2d0e13 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -1251,6 +1251,14 @@ static int journal_get_superblock(journal_t *journal)
> 		goto out;
> 	}
> 
> +	if (be32_to_cpu(sb->s_first) == 0 ||
> +		be32_to_cpu(sb->s_first) >= journal->j_maxlen) {

(style) same.

> +		printk(KERN_WARNING
> +			"JBD2: Invalid start block of journal: %u\n",
> +			be32_to_cpu(sb->s_first));
> +		goto out;
> +	}
> +
> 	return 0;

Looks fine otherwise.

Cheers, Andreas





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Jan Kara - Nov. 1, 2011, 10:29 p.m.
On Tue 01-11-11 10:05:03, Eryu Guan wrote:
> I hit a J_ASSERT(blocknr != 0) failure in cleanup_journal_tail() when
> mounting a fsfuzzed ext3 image. It turns out that the corrupted ext3
> image has s_first = 0 in journal superblock, and the 0 is passed to
> journal->j_head in journal_reset(), then to blocknr in
> cleanup_journal_tail(), in the end the J_ASSERT failed.
> 
> So validate s_first after reading journal superblock from disk in
> journal_get_superblock() to ensure s_first is valid.
> 
> The following script could reproduce it:
> 
> fstype=ext3
> blocksize=1024
> img=$fstype.img
> offset=0
> found=0
> magic="c0 3b 39 98"
> 
> dd if=/dev/zero of=$img bs=1M count=8
> mkfs -t $fstype -b $blocksize -F $img
> filesize=`stat -c %s $img`
> while [ $offset -lt $filesize ]
> do
>         if od -j $offset -N 4 -t x1 $img | grep -i "$magic";then
>                 echo "Found journal: $offset"
>                 found=1
>                 break
>         fi
>         offset=`echo "$offset+$blocksize" | bc`
> done
> 
> if [ $found -ne 1 ];then
>         echo "Magic \"$magic\" not found"
>         exit 1
> fi
> 
> dd if=/dev/zero of=$img seek=$(($offset+23)) conv=notrunc bs=1 count=1
> 
> mkdir -p ./mnt
> mount -o loop $img ./mnt
  Thanks. I've fixed-up the style problems pointed out by Andreas and added
the patch to my tree.

								Honza

> 
> Cc: Jan Kara <jack@suse.cz>
> Cc: "Theodore Ts'o" <tytso@mit.edu>
> Signed-off-by: Eryu Guan <guaneryu@gmail.com>
> ---
>  fs/jbd/journal.c  |    8 ++++++++
>  fs/jbd2/journal.c |    8 ++++++++
>  2 files changed, 16 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c
> index 9fe061f..0c401de 100644
> --- a/fs/jbd/journal.c
> +++ b/fs/jbd/journal.c
> @@ -1135,6 +1135,14 @@ static int journal_get_superblock(journal_t *journal)
>  		goto out;
>  	}
>  
> +	if (be32_to_cpu(sb->s_first) == 0 ||
> +		be32_to_cpu(sb->s_first) >= journal->j_maxlen) {
> +		printk(KERN_WARNING
> +			"JBD: Invalid start block of journal: %u\n",
> +			be32_to_cpu(sb->s_first));
> +		goto out;
> +	}
> +
>  	return 0;
>  
>  out:
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index f24df13..e2d0e13 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -1251,6 +1251,14 @@ static int journal_get_superblock(journal_t *journal)
>  		goto out;
>  	}
>  
> +	if (be32_to_cpu(sb->s_first) == 0 ||
> +		be32_to_cpu(sb->s_first) >= journal->j_maxlen) {
> +		printk(KERN_WARNING
> +			"JBD2: Invalid start block of journal: %u\n",
> +			be32_to_cpu(sb->s_first));
> +		goto out;
> +	}
> +
>  	return 0;
>  
>  out:
> -- 
> 1.7.7.1
>
Theodore Ts'o - Nov. 1, 2011, 11:06 p.m.
On Tue, Nov 01, 2011 at 10:05:03AM +0800, Eryu Guan wrote:
> I hit a J_ASSERT(blocknr != 0) failure in cleanup_journal_tail() when
> mounting a fsfuzzed ext3 image. It turns out that the corrupted ext3
> image has s_first = 0 in journal superblock, and the 0 is passed to
> journal->j_head in journal_reset(), then to blocknr in
> cleanup_journal_tail(), in the end the J_ASSERT failed.
> 
> So validate s_first after reading journal superblock from disk in
> journal_get_superblock() to ensure s_first is valid.
>
> ...
> 
> Signed-off-by: Eryu Guan <guaneryu@gmail.com>

Thanks, applied.  (I took the jbd fixup as well, since it's obvious)

					- Ted
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Theodore Ts'o - Nov. 1, 2011, 11:16 p.m.
On Tue, Nov 01, 2011 at 11:29:55PM +0100, Jan Kara wrote:
>   Thanks. I've fixed-up the style problems pointed out by Andreas and added
> the patch to my tree.

Oops, I grabbed it too.  How do you want to resolve this?  I can just
carry the jbd2 change, or I can carry both, or I can let you carry
both.  Either is fine with me.  (And if we both carry it git should do
the right thing anyway.  :-)

						- Ted
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Jan Kara - Nov. 2, 2011, 2:24 p.m.
On Tue 01-11-11 19:16:27, Ted Tso wrote:
> On Tue, Nov 01, 2011 at 11:29:55PM +0100, Jan Kara wrote:
> >   Thanks. I've fixed-up the style problems pointed out by Andreas and added
> > the patch to my tree.
> 
> Oops, I grabbed it too.  How do you want to resolve this?  I can just
> carry the jbd2 change, or I can carry both, or I can let you carry
> both.  Either is fine with me.  (And if we both carry it git should do
> the right thing anyway.  :-)
  OK, carry it, I'll remove the patch from my tree.

								Honza

Patch

diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c
index 9fe061f..0c401de 100644
--- a/fs/jbd/journal.c
+++ b/fs/jbd/journal.c
@@ -1135,6 +1135,14 @@  static int journal_get_superblock(journal_t *journal)
 		goto out;
 	}
 
+	if (be32_to_cpu(sb->s_first) == 0 ||
+		be32_to_cpu(sb->s_first) >= journal->j_maxlen) {
+		printk(KERN_WARNING
+			"JBD: Invalid start block of journal: %u\n",
+			be32_to_cpu(sb->s_first));
+		goto out;
+	}
+
 	return 0;
 
 out:
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index f24df13..e2d0e13 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -1251,6 +1251,14 @@  static int journal_get_superblock(journal_t *journal)
 		goto out;
 	}
 
+	if (be32_to_cpu(sb->s_first) == 0 ||
+		be32_to_cpu(sb->s_first) >= journal->j_maxlen) {
+		printk(KERN_WARNING
+			"JBD2: Invalid start block of journal: %u\n",
+			be32_to_cpu(sb->s_first));
+		goto out;
+	}
+
 	return 0;
 
 out: