| From a969d570ffeb680d00db25573727611a923ed163 Mon Sep 17 00:00:00 2001 |
| From: Eryu Guan <guaneryu@gmail.com> |
| Date: Tue, 1 Nov 2011 19:04:59 -0400 |
| Subject: [PATCH] jbd/jbd2: validate sb->s_first in journal_get_superblock() |
| |
| commit 8762202dd0d6e46854f786bdb6fb3780a1625efe upstream. |
| |
| 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> |
| Signed-off-by: Eryu Guan <guaneryu@gmail.com> |
| Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| --- |
| fs/jbd/journal.c | 8 ++++++++ |
| fs/jbd2/journal.c | 8 ++++++++ |
| 2 files changed, 16 insertions(+) |
| |
| diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c |
| index 45905ff..70713d5 100644 |
| --- a/fs/jbd/journal.c |
| +++ b/fs/jbd/journal.c |
| @@ -1070,6 +1070,14 @@ 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 c03d4dc..7f16fea 100644 |
| --- a/fs/jbd2/journal.c |
| +++ b/fs/jbd2/journal.c |
| @@ -1186,6 +1186,14 @@ 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: |
| -- |
| 1.7.12.1 |
| |