LinuxLists.cc - [PATCH v2] xen-blkfront: fix kernel panic with negotiate

2018-10-30 16:49:22

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

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: [email protected]
Fixes: 7ed8ce1c5fc7 ("xen-blkfront: move negotiate_mq to cover all cases of new VBDs")
Signed-off-by: Manjunath Patil <[email protected]>
---
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

2018-10-30 16:55:10

by Jürgen Groß

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

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: [email protected]
> Fixes: 7ed8ce1c5fc7 ("xen-blkfront: move negotiate_mq to cover all cases of new VBDs")
> Signed-off-by: Manjunath Patil <[email protected]>

Reviewed-by: Juergen Gross <[email protected]>

Juergen

2018-10-31 08:23:12

by Roger Pau Monne

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

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: [email protected]
> Fixes: 7ed8ce1c5fc7 ("xen-blkfront: move negotiate_mq to cover all cases of new VBDs")
> Signed-off-by: Manjunath Patil <[email protected]>

Acked-by: Roger Pau Monn? <[email protected]>

Thanks, Roger.

2018-11-06 09:39:16

by Jürgen Groß

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