rcutorture: Check nfakewriters parameter

Currently, a negative value for rcutorture.nfakewriters= can cause
rcutorture to pass a negative size to the memory allocator, which
is not really a particularly good thing to do.  This commit therefore
adds bounds checking to this parameter, so that values that are less
than or equal to zero disable fake writing.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 9 insertions, 6 deletions

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 7e29a3266139..2cbe569ac5dd 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1786,12 +1786,15 @@ rcu_torture_init(void)
                                           writer_task);
         if (firsterr)
                 goto unwind;
-        fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
-                                   GFP_KERNEL);
-        if (fakewriter_tasks == NULL) {
-                VERBOSE_TOROUT_ERRSTRING("out of memory");
-                firsterr = -ENOMEM;
-                goto unwind;
+        if (nfakewriters > 0) {
+                fakewriter_tasks = kzalloc(nfakewriters *
+                                           sizeof(fakewriter_tasks[0]),
+                                           GFP_KERNEL);
+                if (fakewriter_tasks == NULL) {
+                        VERBOSE_TOROUT_ERRSTRING("out of memory");
+                        firsterr = -ENOMEM;
+                        goto unwind;
+                }
         }
         for (i = 0; i < nfakewriters; i++) {
                 firsterr = torture_create_kthread(rcu_torture_fakewriter,