Fix clear_refs_write() use of struct mm_walk

Don't use a static entry, so as to prevent races during concurrent use
of this function.

Reported-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index ab8ccc9..05053d7 100644 (file)
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -476,10 +476,10 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
                return -ESRCH;
        mm = get_task_mm(task);
        if (mm) {
-               static struct mm_walk clear_refs_walk;
-               memset(&clear_refs_walk, 0, sizeof(clear_refs_walk));
-               clear_refs_walk.pmd_entry = clear_refs_pte_range;
-               clear_refs_walk.mm = mm;
+               struct mm_walk clear_refs_walk = {
+                       .pmd_entry = clear_refs_pte_range,
+                       .mm = mm,
+               };
                down_read(&mm->mmap_sem);
                for (vma = mm->mmap; vma; vma = vma->vm_next) {
                        clear_refs_walk.private = vma;