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    Subject[PATCH 4.19 301/361] xen-blkfront: fix kernel panic with negotiate_mq error path
    Date
    4.19-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Manjunath Patil <manjunath.b.patil@oracle.com>

    commit 6cc4a0863c9709c512280c64e698d68443ac8053 upstream.

    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>
    Signed-off-by: Juergen Gross <jgross@suse.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/block/xen-blkfront.c | 1 +
    1 file changed, 1 insertion(+)

    --- a/drivers/block/xen-blkfront.c
    +++ b/drivers/block/xen-blkfront.c
    @@ -1919,6 +1919,7 @@ static int negotiate_mq(struct blkfront_
    GFP_KERNEL);
    if (!info->rinfo) {
    xenbus_dev_fatal(info->xbdev, -ENOMEM, "allocating ring_info structure");
    + info->nr_rings = 0;
    return -ENOMEM;
    }


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