mtd: mtd_torturetest can cause stack overflows

mtd_torturetest uses the module parm "ebcnt" to control the size of a
stack based array of int's. When "ebcnt" is large, Ex: 1000, it
causes stack overflows on systems with small kernel stacks. The fix
is to move the array from the stack to kmalloc memory.

Signed-off-by: Al Cooper <alcooperx@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

1 files changed, 11 insertions, 14 deletions

diff --git a/drivers/mtd/tests/mtd_torturetest.c b/drivers/mtd/tests/mtd_torturetest.c
index c4cde1e9eddb..3a9f6a6a79f9 100644
--- a/drivers/mtd/tests/mtd_torturetest.c
+++ b/drivers/mtd/tests/mtd_torturetest.c
@@ -208,7 +208,7 @@ static inline int write_pattern(int ebnum, void *buf)
 static int __init tort_init(void)
 {
         int err = 0, i, infinite = !cycles_count;
-        int bad_ebs[ebcnt];
+        int *bad_ebs;
 
         printk(KERN_INFO "\n");
         printk(KERN_INFO "=================================================\n");
@@ -250,28 +250,24 @@ static int __init tort_init(void)
 
         err = -ENOMEM;
         patt_5A5 = kmalloc(mtd->erasesize, GFP_KERNEL);
-        if (!patt_5A5) {
-                pr_err("error: cannot allocate memory\n");
+        if (!patt_5A5)
                 goto out_mtd;
-        }
 
         patt_A5A = kmalloc(mtd->erasesize, GFP_KERNEL);
-        if (!patt_A5A) {
-                pr_err("error: cannot allocate memory\n");
+        if (!patt_A5A)
                 goto out_patt_5A5;
-        }
 
         patt_FF = kmalloc(mtd->erasesize, GFP_KERNEL);
-        if (!patt_FF) {
-                pr_err("error: cannot allocate memory\n");
+        if (!patt_FF)
                 goto out_patt_A5A;
-        }
 
         check_buf = kmalloc(mtd->erasesize, GFP_KERNEL);
-        if (!check_buf) {
-                pr_err("error: cannot allocate memory\n");
+        if (!check_buf)
                 goto out_patt_FF;
-        }
+
+        bad_ebs = kcalloc(ebcnt, sizeof(*bad_ebs), GFP_KERNEL);
+        if (!bad_ebs)
+                goto out_check_buf;
 
         err = 0;
 
@@ -290,7 +286,6 @@ static int __init tort_init(void)
         /*
          * Check if there is a bad eraseblock among those we are going to test.
          */
-        memset(&bad_ebs[0], 0, sizeof(int) * ebcnt);
         if (mtd_can_have_bb(mtd)) {
                 for (i = eb; i < eb + ebcnt; i++) {
                         err = mtd_block_isbad(mtd, (loff_t)i * mtd->erasesize);
@@ -394,6 +389,8 @@ out:
 
         pr_info("finished after %u erase cycles\n",
                erase_cycles);
+        kfree(bad_ebs);
+out_check_buf:
         kfree(check_buf);
 out_patt_FF:
         kfree(patt_FF);