lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Sun, 14 Aug 2011 13:01:01 -0700
From:	Curt Wohlgemuth <curtw@...gle.com>
To:	"Theodore Ts'o" <tytso@....edu>
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] jbd2: instrument jh on wrong transaction BUG_ON's

Hi Ted:

Unfortunately, some deref in your printk didn't go over too well:

[  970.871166] BUG: unable to handle kernel NULL pointer dereference
at 0000000000000008
[  970.872139] IP: [<ffffffff812a158e>] jbd2_journal_dirty_metadata+0x18e/0x220
[  970.872139] PGD 857b8d067 PUD 852f26067 PMD 0
[  970.872139] Oops: 0000 [#1] SMP
[  970.872139] CPU 14
...
[  970.872139] Call Trace:
[  970.872139]  [<ffffffff812a9d26>] ? jbd2_journal_add_journal_head+0x86/0x290
[  970.872139]  [<ffffffff8125c87c>] ? __ext4_journalled_writepage+0xac/0x390
[  970.872139]  [<ffffffff812848b3>] __ext4_handle_dirty_metadata+0x83/0x120
[  970.872139]  [<ffffffff81284c1e>] ? __ext4_journal_get_write_access+0x3e/0x80
[  970.872139]  [<ffffffff8125cac8>] __ext4_journalled_writepage+0x2f8/0x390
[  970.872139]  [<ffffffff8125e264>] ext4_writepage+0x234/0x2f0
[  970.872139]  [<ffffffff81155ad7>] __writepage+0x17/0x40
...

where the IP corresponds to:

(gdb) list *0xffffffff812a158e
0xffffffff812a158e is in jbd2_journal_dirty_metadata
(fs/jbd2/transaction.c:1124).
1119             */
1120            if (jh->b_transaction != transaction) {
1121                    JBUFFER_TRACE(jh, "already on other transaction");
1122                    if (unlikely(jh->b_transaction !=
1123                                 journal->j_committing_transaction)) {
1124                            printk(KERN_EMERG "JBD: %s: "
1125                                   "jh->b_transaction (%llu, %p, %u) != "
1126
"journal->j_committing_transaction (%p, %u)",
1127                                   journal->j_devname,
1128                                   (unsigned long long) bh->b_blocknr,

It seems that  jh->b_transaction is NULL, and deferencing it to print
out jh->b_transaction->t_tid causes the NULL pointer deref.

Curt

On Sat, Aug 13, 2011 at 7:53 PM, Theodore Ts'o <tytso@....edu> wrote:
> These assertions have been reported as being tripped.  Instrument them
> so we get more information about what might be going on.
>
> Cc: curtw@...gle.com
> Signed-off-by: "Theodore Ts'o" <tytso@....edu>
> ---
>
> Curt, you might want to see if you can replicate that jbd2 crash with
> this patch applied.  Hopefully we'll get more information about what is
> going on.
>
>  fs/jbd2/transaction.c |   42 +++++++++++++++++++++++++++++++++++++-----
>  1 files changed, 37 insertions(+), 5 deletions(-)
>
> diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
> index 2d71094..693fe63 100644
> --- a/fs/jbd2/transaction.c
> +++ b/fs/jbd2/transaction.c
> @@ -1093,8 +1093,19 @@ int jbd2_journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
>         */
>        if (jh->b_transaction == transaction && jh->b_jlist == BJ_Metadata) {
>                JBUFFER_TRACE(jh, "fastpath");
> -               J_ASSERT_JH(jh, jh->b_transaction ==
> -                                       journal->j_running_transaction);
> +               if (unlikely(jh->b_transaction !=
> +                            journal->j_running_transaction)) {
> +                       printk(KERN_EMERG "JBD: %s: "
> +                              "jh->b_transaction (%llu, %p, %u) != "
> +                              "journal->j_running_transaction (%p, %u)",
> +                              journal->j_devname,
> +                              (unsigned long long) bh->b_blocknr,
> +                              jh->b_transaction,
> +                              jh->b_transaction->t_tid,
> +                              journal->j_running_transaction,
> +                              journal->j_running_transaction->t_tid);
> +                       BUG_ON(1);
> +               }
>                goto out_unlock_bh;
>        }
>
> @@ -1108,9 +1119,30 @@ int jbd2_journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
>         */
>        if (jh->b_transaction != transaction) {
>                JBUFFER_TRACE(jh, "already on other transaction");
> -               J_ASSERT_JH(jh, jh->b_transaction ==
> -                                       journal->j_committing_transaction);
> -               J_ASSERT_JH(jh, jh->b_next_transaction == transaction);
> +               if (unlikely(jh->b_transaction !=
> +                            journal->j_committing_transaction)) {
> +                       printk(KERN_EMERG "JBD: %s: "
> +                              "jh->b_transaction (%llu, %p, %u) != "
> +                              "journal->j_committing_transaction (%p, %u)",
> +                              journal->j_devname,
> +                              (unsigned long long) bh->b_blocknr,
> +                              jh->b_transaction,
> +                              jh->b_transaction->t_tid,
> +                              journal->j_committing_transaction,
> +                              journal->j_committing_transaction->t_tid);
> +                       BUG_ON(1);
> +               }
> +               if (unlikely(jh->b_next_transaction != transaction)) {
> +                       printk(KERN_EMERG "JBD: %s: "
> +                              "jh->b_next_transaction (%llu, %p, %u) != "
> +                              "transaction (%p, %u)",
> +                              journal->j_devname,
> +                              (unsigned long long) bh->b_blocknr,
> +                              jh->b_next_transaction,
> +                              jh->b_next_transaction->t_tid,
> +                              transaction, transaction->t_tid);
> +                       BUG_ON(1);
> +               }
>                /* And this case is illegal: we can't reuse another
>                 * transaction's data buffer, ever. */
>                goto out_unlock_bh;
> --
> 1.7.4.1.22.gec8e1.dirty
>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Powered by blists - more mailing lists