linux-kernel - [PATCH] ipc,msg: drop dst nil validation in copy

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Date:	Wed, 14 Oct 2015 07:16:48 -0700
From:	Davidlohr Bueso <dave@...olabs.net>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Stanislav Kinsbursky <skinsbursky@...allels.com>,
	linux-kernel@...r.kernel.org, dave@...olabs.net
Subject: [PATCH] ipc,msg: drop dst nil validation in copy_msg

d0edd8528362 (ipc: convert invalid scenarios to use WARN_ON)
relaxed the nil dst parameter check, originally being a full
BUG_ON. However, this check seems quite unnecessary when the
only purpose is for ceckpoint/restore (MSG_COPY flag):

o The copy variable is set initially to nil, apparently as a
way of ensuring that prepare_copy is previously called. Which
is in fact done, unconditionally at the beginning of do_msgrcv.

o There is no concurrency with 'copy' (stack allocated in
do_msgrcv).

Furthermore, any errors in 'copy' (and thus prepare_copy/copy_msg)
should always handled by IS_ERR() family. Therefore remove this
check altogether as it can never occur with the current users.

Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
---
  ipc/msgutil.c | 1 -
  1 file changed, 1 deletion(-)

diff --git a/ipc/msgutil.c b/ipc/msgutil.c
index 71f448e..ed81aaf 100644
--- a/ipc/msgutil.c
+++ b/ipc/msgutil.c
@@ -123,7 +123,6 @@ struct msg_msg *copy_msg(struct msg_msg *src, struct msg_msg *dst)
	size_t len = src->m_ts;
	size_t alen;

-	WARN_ON(dst == NULL);
	if (src->m_ts > dst->m_ts)
		return ERR_PTR(-EINVAL);

--
2.1.4
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