Re: [Bug #14894] pohmelfs: NULL pointer dereference

Jens Axboe
2009-12-30T09:14:37Z

On Tue, Dec 29 2009, Rafael J. Wysocki wrote:
> On Tuesday 29 December 2009, Evgeniy Polyakov wrote:
> > On Tue, Dec 29, 2009 at 04:28:52PM +0100, Rafael J. Wysocki (rjw@sisk.pl) wrote:
> > > This message has been generated automatically as a part of a report
> > > of regressions introduced between 2.6.31 and 2.6.32.
> > >
> > > The following bug entry is on the current list of known regressions
> > > introduced between 2.6.31 and 2.6.32. Please verify if it still should
> > > be listed and let me know (either way).
> > >
> > >
> > > Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=14894
> > > Subject : pohmelfs: NULL pointer dereference
> > > Submitter : Alexander Beregalov <a.beregalov@gmail.com>
> > > Date : 2009-12-02 1:11 (28 days old)
> > > References : http://marc.info/?l=linux-kernel&m=125971633107940&w=4
> > > Handled-By : Evgeniy Polyakov <zbr@ioremap.net>
> >
> > Yes, I saw this regression and there is a patch to handle this, but it
> > kind of disables sync at all. Jens Axboe, who introduced per-bdi
> > writeback patches, did not yet reply.
>
> Well, Jens, what's your opinion about that?

Since pohmelfs isn't tied to a single block device, it needs to setup a
backing dev like nfs/btrfs/etc do. Here's a completely untested patch.

diff --git a/drivers/staging/pohmelfs/inode.c b/drivers/staging/pohmelfs/inode.c
index f69b778..cd25811 100644
--- a/drivers/staging/pohmelfs/inode.c
+++ b/drivers/staging/pohmelfs/inode.c
@@ -36,6 +36,7 @@
#define POHMELFS_MAGIC_NUM 0x504f482e

static struct kmem_cache *pohmelfs_inode_cache;
+static atomic_t psb_bdi_num = ATOMIC_INIT(0);

/*
* Removes inode from all trees, drops local name cache and removes all queued
@@ -1331,6 +1332,8 @@ static void pohmelfs_put_super(struct super_block *sb)
pohmelfs_crypto_exit(psb);
pohmelfs_state_exit(psb);

+ bdi_destroy(&psb->bdi);
+
kfree(psb);
sb->s_fs_info = NULL;
}
@@ -1815,11 +1818,22 @@ static int pohmelfs_fill_super(struct super_block *sb, void *data, int silent)
if (!psb)
goto err_out_exit;

+ err = bdi_init(&psb->bdi);
+ if (err)
+ goto err_out_free_sb;
+
+ err = bdi_register(&psb->bdi, NULL, "pfs-%d", atomic_inc_return(&psb_bdi_num));
+ if (err) {
+ bdi_destroy(&psb->bdi);
+ goto err_out_free_sb;
+ }
+
sb->s_fs_info = psb;
sb->s_op = &pohmelfs_sb_ops;
sb->s_magic = POHMELFS_MAGIC_NUM;
sb->s_maxbytes = MAX_LFS_FILESIZE;
sb->s_blocksize = PAGE_SIZE;
+ sb->s_bdi = &psb->bdi;

psb->sb = sb;

@@ -1863,11 +1877,11 @@ static int pohmelfs_fill_super(struct super_block *sb, void *data, int silent)

err = pohmelfs_parse_options((char *) data, psb, 0);
if (err)
- goto err_out_free_sb;
+ goto err_out_free_bdi;

err = pohmelfs_copy_crypto(psb);
if (err)
- goto err_out_free_sb;
+ goto err_out_free_bdi;

err = pohmelfs_state_init(psb);
if (err)
@@ -1916,6 +1930,8 @@ err_out_state_exit:
err_out_free_strings:
kfree(psb->cipher_string);
kfree(psb->hash_string);
+err_out_free_bdi:
+ bdi_destroy(&psb->bdi);
err_out_free_sb:
kfree(psb);
err_out_exit:
diff --git a/drivers/staging/pohmelfs/netfs.h b/drivers/staging/pohmelfs/netfs.h
index 623a07d..01cba00 100644
--- a/drivers/staging/pohmelfs/netfs.h
+++ b/drivers/staging/pohmelfs/netfs.h
@@ -18,6 +18,7 @@

#include <linux/types.h>
#include <linux/connector.h>
+#include <linux/backing-dev.h>

#define POHMELFS_CN_IDX 5
#define POHMELFS_CN_VAL 0
@@ -624,6 +625,8 @@ struct pohmelfs_sb {

struct super_block *sb;

+ struct backing_dev_info bdi;
+
/*
* Algorithm strings.
*/

--
Jens Axboe