[PATCH] xfrm: Fix return value check of copy_sec_ctx.

[Dmitry Shmidt <dimitrysh@xxxxxxxxxx>]

Please add this patch to stable 3.18, 4.4 and 4.9
It exists in 4.14.
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commit 8598112d04af21cf6c895670e72dcb8a9f58e74f
Author: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Date:   Thu Aug 31 10:37:00 2017 +0200

    xfrm: Fix return value check of copy_sec_ctx.

    A recent commit added an output_mark. When copying
    this output_mark, the return value of copy_sec_ctx
    is overwitten without a check. Fix this by copying
    the output_mark before the security context.

    Fixes: 077fbac405bf ("net: xfrm: support setting an output mark.")
    Signed-off-by: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>