diff mbox

[9/10] IB/qib: use safer test on the result of find_first_zero_bit

Message ID 1401872880-23685-10-git-send-email-Julia.Lawall@lip6.fr (mailing list archive)
State Rejected
Headers show

Commit Message

Julia Lawall June 4, 2014, 9:07 a.m. UTC 
From: Julia Lawall <Julia.Lawall@lip6.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@lip6.fr>

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


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Comments

Marciniszyn, Mike June 4, 2014, 6:41 p.m. UTC | #1 
> Subject: [PATCH 9/10] IB/qib: use safer test on the result of find_first_zero_bit
> 
> From: Julia Lawall <Julia.Lawall@lip6.fr>

Thanks for the patch!

Roland, I'm marking this as stable since a memory corruption can occur in the _set_bit().

Cc: <stable@vger.kernel.org>
Acked-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
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Julia Lawall June 4, 2014, 7:19 p.m. UTC | #2 
On Wed, 4 Jun 2014, Marciniszyn, Mike wrote:

> > Subject: [PATCH 9/10] IB/qib: use safer test on the result of find_first_zero_bit
> > 
> > From: Julia Lawall <Julia.Lawall@lip6.fr>
> 
> Thanks for the patch!
> 
> Roland, I'm marking this as stable since a memory corruption can occur in the _set_bit().

No, it's not necessary.  It turns out that the result cannot be greater 
than the requested maximum value.

julia
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Marciniszyn, Mike June 4, 2014, 8:03 p.m. UTC | #3 
> 
> No, it's not necessary.  It turns out that the result cannot be greater than the
> requested maximum value.
> 
> Julia

Ok. 

No stable then.

Mike
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diff mbox

Patch

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);