[PATCH v2] xen-blkfront: fix kernel panic with negotiate_mq error path

[PATCH v2] xen-blkfront: fix kernel panic with negotiate_mq error path

[Manjunath Patil]

info->nr_rings isn't adjusted in case of ENOMEM error from
negotiate_mq(). This leads to kernel panic in error path.

Typical call stack involving panic -
 #8 page_fault at ffffffff8175936f
    [exception RIP: blkif_free_ring+33]
    RIP: ffffffffa0149491  RSP: ffff8804f7673c08  RFLAGS: 00010292
 ...
 #9 blkif_free at ffffffffa0149aaa [xen_blkfront]
 #10 talk_to_blkback at ffffffffa014c8cd [xen_blkfront]
 #11 blkback_changed at ffffffffa014ea8b [xen_blkfront]
 #12 xenbus_otherend_changed at ffffffff81424670
 #13 backend_changed at ffffffff81426dc3
 #14 xenwatch_thread at ffffffff81422f29
 #15 kthread at ffffffff810abe6a
 #16 ret_from_fork at ffffffff81754078

Cc: stable@vger.kernel.org
Fixes: 7ed8ce1c5fc7 ("xen-blkfront: move negotiate_mq to cover all cases of new VBDs")
Signed-off-by: Manjunath Patil <manjunath.b.patil@oracle.com>
---
 drivers/block/xen-blkfront.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 429d201..5d84da2 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1919,6 +1919,7 @@ static int negotiate_mq(struct blkfront_info *info)
 			      GFP_KERNEL);
 	if (!info->rinfo) {
 		xenbus_dev_fatal(info->xbdev, -ENOMEM, "allocating ring_info structure");
+		info->nr_rings = 0;
 		return -ENOMEM;
 	}
 
-- 
1.7.1

Re: [PATCH v2] xen-blkfront: fix kernel panic with negotiate_mq error path

[Juergen Gross]

On 30/10/2018 17:49, Manjunath Patil wrote:
> info->nr_rings isn't adjusted in case of ENOMEM error from
> negotiate_mq(). This leads to kernel panic in error path.
> 
> Typical call stack involving panic -
>  #8 page_fault at ffffffff8175936f
>     [exception RIP: blkif_free_ring+33]
>     RIP: ffffffffa0149491  RSP: ffff8804f7673c08  RFLAGS: 00010292
>  ...
>  #9 blkif_free at ffffffffa0149aaa [xen_blkfront]
>  #10 talk_to_blkback at ffffffffa014c8cd [xen_blkfront]
>  #11 blkback_changed at ffffffffa014ea8b [xen_blkfront]
>  #12 xenbus_otherend_changed at ffffffff81424670
>  #13 backend_changed at ffffffff81426dc3
>  #14 xenwatch_thread at ffffffff81422f29
>  #15 kthread at ffffffff810abe6a
>  #16 ret_from_fork at ffffffff81754078
> 
> Cc: stable@vger.kernel.org
> Fixes: 7ed8ce1c5fc7 ("xen-blkfront: move negotiate_mq to cover all cases of new VBDs")
> Signed-off-by: Manjunath Patil <manjunath.b.patil@oracle.com>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen

Re: [PATCH v2] xen-blkfront: fix kernel panic with negotiate_mq error path

[Roger Pau Monné]

On Tue, Oct 30, 2018 at 09:49:21AM -0700, Manjunath Patil wrote:
> info->nr_rings isn't adjusted in case of ENOMEM error from
> negotiate_mq(). This leads to kernel panic in error path.
> 
> Typical call stack involving panic -
>  #8 page_fault at ffffffff8175936f
>     [exception RIP: blkif_free_ring+33]
>     RIP: ffffffffa0149491  RSP: ffff8804f7673c08  RFLAGS: 00010292
>  ...
>  #9 blkif_free at ffffffffa0149aaa [xen_blkfront]
>  #10 talk_to_blkback at ffffffffa014c8cd [xen_blkfront]
>  #11 blkback_changed at ffffffffa014ea8b [xen_blkfront]
>  #12 xenbus_otherend_changed at ffffffff81424670
>  #13 backend_changed at ffffffff81426dc3
>  #14 xenwatch_thread at ffffffff81422f29
>  #15 kthread at ffffffff810abe6a
>  #16 ret_from_fork at ffffffff81754078
> 
> Cc: stable@vger.kernel.org
> Fixes: 7ed8ce1c5fc7 ("xen-blkfront: move negotiate_mq to cover all cases of new VBDs")
> Signed-off-by: Manjunath Patil <manjunath.b.patil@oracle.com>

Acked-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks, Roger.

Re: [PATCH v2] xen-blkfront: fix kernel panic with negotiate_mq error path

[Juergen Gross]

On 30/10/2018 17:49, Manjunath Patil wrote:
> info->nr_rings isn't adjusted in case of ENOMEM error from
> negotiate_mq(). This leads to kernel panic in error path.
> 
> Typical call stack involving panic -
>  #8 page_fault at ffffffff8175936f
>     [exception RIP: blkif_free_ring+33]
>     RIP: ffffffffa0149491  RSP: ffff8804f7673c08  RFLAGS: 00010292
>  ...
>  #9 blkif_free at ffffffffa0149aaa [xen_blkfront]
>  #10 talk_to_blkback at ffffffffa014c8cd [xen_blkfront]
>  #11 blkback_changed at ffffffffa014ea8b [xen_blkfront]
>  #12 xenbus_otherend_changed at ffffffff81424670
>  #13 backend_changed at ffffffff81426dc3
>  #14 xenwatch_thread at ffffffff81422f29
>  #15 kthread at ffffffff810abe6a
>  #16 ret_from_fork at ffffffff81754078
> 
> Cc: stable@vger.kernel.org
> Fixes: 7ed8ce1c5fc7 ("xen-blkfront: move negotiate_mq to cover all cases of new VBDs")
> Signed-off-by: Manjunath Patil <manjunath.b.patil@oracle.com>

Pushed to xen.git for-linus-4.20a


Juergen