linux-kernel - [PATCH 9/10] IB/qib: use safer test on the result of find_first_zero

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Message-Id: <1401872880-23685-10-git-send-email-Julia.Lawall@lip6.fr>
Date:	Wed,  4 Jun 2014 11:07:59 +0200
From:	Julia Lawall <Julia.Lawall@...6.fr>
To:	Mike Marciniszyn <infinipath@...el.com>
Cc:	kernel-janitors@...r.kernel.org, Roland Dreier <roland@...nel.org>,
	Sean Hefty <sean.hefty@...el.com>,
	Hal Rosenstock <hal.rosenstock@...il.com>,
	linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 9/10] IB/qib: use safer test on the result of find_first_zero_bit

From: Julia Lawall <Julia.Lawall@...6.fr>

Find_first_zero_bit considers BITS_PER_LONG bits at a time, and thus may
return a larger number than the maximum position argument if that position
is not a multiple of BITS_PER_LONG.

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression e1,e2,e3;
statement S1,S2;
@@

e1 = find_first_zero_bit(e2,e3)
...
if (e1 
- ==
+ >=
  e3)
S1 else S2
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@...6.fr>

---
 drivers/infiniband/hw/qib/qib_file_ops.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff -u -p a/drivers/infiniband/hw/qib/qib_file_ops.c b/drivers/infiniband/hw/qib/qib_file_ops.c
--- a/drivers/infiniband/hw/qib/qib_file_ops.c
+++ b/drivers/infiniband/hw/qib/qib_file_ops.c
@@ -1187,7 +1187,7 @@ static void assign_ctxt_affinity(struct
 		int cpu;
 		cpu = find_first_zero_bit(qib_cpulist,
 					  qib_cpulist_count);
-		if (cpu == qib_cpulist_count)
+		if (cpu >= qib_cpulist_count)
 			qib_dev_err(dd,
 			"no cpus avail for affinity PID %u\n",
 			current->pid);

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