Patch "MIPS: smp.c: Fix uninitialised temp_foreign_map" has been added to the 4.4-stable tree

Patch "MIPS: smp.c: Fix uninitialised temp_foreign_map" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    MIPS: smp.c: Fix uninitialised temp_foreign_map

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mips-smp.c-fix-uninitialised-temp_foreign_map.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From d825c06bfe8b885b797f917ad47365d0e9c21fbb Mon Sep 17 00:00:00 2001
From: James Hogan <james.hogan@imgtec.com>
Date: Fri, 4 Mar 2016 10:10:51 +0000
Subject: MIPS: smp.c: Fix uninitialised temp_foreign_map

From: James Hogan <james.hogan@imgtec.com>

commit d825c06bfe8b885b797f917ad47365d0e9c21fbb upstream.

When calculate_cpu_foreign_map() recalculates the cpu_foreign_map
cpumask it uses the local variable temp_foreign_map without initialising
it to zero. Since the calculation only ever sets bits in this cpumask
any existing bits at that memory location will remain set and find their
way into cpu_foreign_map too. This could potentially lead to cache
operations suboptimally doing smp calls to multiple VPEs in the same
core, even though the VPEs share primary caches.

Therefore initialise temp_foreign_map using cpumask_clear() before use.

Fixes: cccf34e9411c ("MIPS: c-r4k: Fix cache flushing for MT cores")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/12759/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/kernel/smp.c |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -121,6 +121,7 @@ static inline void calculate_cpu_foreign
 	cpumask_t temp_foreign_map;
 
 	/* Re-calculate the mask */
+	cpumask_clear(&temp_foreign_map);
 	for_each_online_cpu(i) {
 		core_present = 0;
 		for_each_cpu(k, &temp_foreign_map)


Patches currently in stable-queue which might be from james.hogan@imgtec.com are

queue-4.4/ld-version-fix-awk-regex-compile-failure.patch
queue-4.4/mips-smp.c-fix-uninitialised-temp_foreign_map.patch