From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932441Ab2F2Ner (ORCPT ); Fri, 29 Jun 2012 09:34:47 -0400 Received: from cantor2.suse.de ([195.135.220.15]:45785 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932370Ab2F2Ndn (ORCPT ); Fri, 29 Jun 2012 09:33:43 -0400 From: Mel Gorman To: Andrew Morton Cc: Linux-MM , Linux-Netdev , Linux-NFS , LKML , David Miller , Trond Myklebust , Neil Brown , Christoph Hellwig , Peter Zijlstra , Mike Christie , Eric B Munson , Sebastian Andrzej Siewior , Mel Gorman Subject: [PATCH 12/12] Avoid dereferencing bd_disk during swap_entry_free for network storage Date: Fri, 29 Jun 2012 14:33:25 +0100 Message-Id: <1340976805-5799-13-git-send-email-mgorman@suse.de> X-Mailer: git-send-email 1.7.9.2 In-Reply-To: <1340976805-5799-1-git-send-email-mgorman@suse.de> References: <1340976805-5799-1-git-send-email-mgorman@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit [b3a27d: swap: Add swap slot free callback to block_device_operations] dereferences p->bdev->bd_disk but this is a NULL dereference if using swap-over-NFS. This patch checks SWP_BLKDEV on the swap_info_struct before dereferencing. With reference to this callback, Christoph Hellwig stated "Please just remove the callback entirely. It has no user outside the staging tree and was added clearly against the rules for that staging tree". This would also be my preference but there was not an obvious way of keeping zram in staging/ happy. Signed-off-by: Xiaotian Feng Signed-off-by: Mel Gorman Acked-by: Rik van Riel --- mm/swapfile.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index 1d77b13..f4c802d 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -549,7 +549,6 @@ static unsigned char swap_entry_free(struct swap_info_struct *p, /* free if no reference */ if (!usage) { - struct gendisk *disk = p->bdev->bd_disk; if (offset < p->lowest_bit) p->lowest_bit = offset; if (offset > p->highest_bit) @@ -560,9 +559,11 @@ static unsigned char swap_entry_free(struct swap_info_struct *p, nr_swap_pages++; p->inuse_pages--; frontswap_invalidate_page(p->type, offset); - if ((p->flags & SWP_BLKDEV) && - disk->fops->swap_slot_free_notify) - disk->fops->swap_slot_free_notify(p->bdev, offset); + if (p->flags & SWP_BLKDEV) { + struct gendisk *disk = p->bdev->bd_disk; + if (disk->fops->swap_slot_free_notify) + disk->fops->swap_slot_free_notify(p->bdev, offset); + } } return usage; -- 1.7.9.2 From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mel Gorman Subject: [PATCH 12/12] Avoid dereferencing bd_disk during swap_entry_free for network storage Date: Fri, 29 Jun 2012 14:33:25 +0100 Message-ID: <1340976805-5799-13-git-send-email-mgorman@suse.de> References: <1340976805-5799-1-git-send-email-mgorman@suse.de> Cc: Linux-MM , Linux-Netdev , Linux-NFS , LKML , David Miller , Trond Myklebust , Neil Brown , Christoph Hellwig , Peter Zijlstra , Mike Christie , Eric B Munson , Sebastian Andrzej Siewior , Mel Gorman To: Andrew Morton Return-path: In-Reply-To: <1340976805-5799-1-git-send-email-mgorman@suse.de> Sender: owner-linux-mm@kvack.org List-Id: netdev.vger.kernel.org Commit [b3a27d: swap: Add swap slot free callback to block_device_operations] dereferences p->bdev->bd_disk but this is a NULL dereference if using swap-over-NFS. This patch checks SWP_BLKDEV on the swap_info_struct before dereferencing. With reference to this callback, Christoph Hellwig stated "Please just remove the callback entirely. It has no user outside the staging tree and was added clearly against the rules for that staging tree". This would also be my preference but there was not an obvious way of keeping zram in staging/ happy. Signed-off-by: Xiaotian Feng Signed-off-by: Mel Gorman Acked-by: Rik van Riel --- mm/swapfile.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index 1d77b13..f4c802d 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -549,7 +549,6 @@ static unsigned char swap_entry_free(struct swap_info_struct *p, /* free if no reference */ if (!usage) { - struct gendisk *disk = p->bdev->bd_disk; if (offset < p->lowest_bit) p->lowest_bit = offset; if (offset > p->highest_bit) @@ -560,9 +559,11 @@ static unsigned char swap_entry_free(struct swap_info_struct *p, nr_swap_pages++; p->inuse_pages--; frontswap_invalidate_page(p->type, offset); - if ((p->flags & SWP_BLKDEV) && - disk->fops->swap_slot_free_notify) - disk->fops->swap_slot_free_notify(p->bdev, offset); + if (p->flags & SWP_BLKDEV) { + struct gendisk *disk = p->bdev->bd_disk; + if (disk->fops->swap_slot_free_notify) + disk->fops->swap_slot_free_notify(p->bdev, offset); + } } return usage; -- 1.7.9.2 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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