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authorKees Cook <keescook@chromium.org>2013-10-24 09:25:39 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-10-29 16:13:39 -0700
commit7d196ac303652588c60350f0a581d71e2e7b1a50 (patch)
tree5bcda7cfe5cdb498abf5ac3c9cbe81ee75bc6813 /drivers/misc
parent629c66a22c21b692b6e58b9c1d8fa56a60ccb52d (diff)
lkdtm: adjust recursion size to avoid warnings
When CONFIG_FRAME_WARN is set low (e.g. some ARM builds), the hard-coded stack buffer size used for kernel stack over run testing triggers build warnings. Instead, avoid the warning by recalcuating the buffer size and recursion count needed to trigger the test. Also uses the recursion counter indirectly to avoid changing the parameter during the test. Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/misc')
-rw-r--r--drivers/misc/lkdtm.c30
1 files changed, 20 insertions, 10 deletions
diff --git a/drivers/misc/lkdtm.c b/drivers/misc/lkdtm.c
index 9cbd0370ca44..482344242f94 100644
--- a/drivers/misc/lkdtm.c
+++ b/drivers/misc/lkdtm.c
@@ -49,8 +49,19 @@
#include <linux/ide.h>
#endif
+/*
+ * Make sure our attempts to over run the kernel stack doesn't trigger
+ * a compiler warning when CONFIG_FRAME_WARN is set. Then make sure we
+ * recurse past the end of THREAD_SIZE by default.
+ */
+#if defined(CONFIG_FRAME_WARN) && (CONFIG_FRAME_WARN > 0)
+#define REC_STACK_SIZE (CONFIG_FRAME_WARN / 2)
+#else
+#define REC_STACK_SIZE (THREAD_SIZE / 8)
+#endif
+#define REC_NUM_DEFAULT ((THREAD_SIZE / REC_STACK_SIZE) * 2)
+
#define DEFAULT_COUNT 10
-#define REC_NUM_DEFAULT 10
#define EXEC_SIZE 64
enum cname {
@@ -140,8 +151,7 @@ static DEFINE_SPINLOCK(lock_me_up);
static u8 data_area[EXEC_SIZE];
module_param(recur_count, int, 0644);
-MODULE_PARM_DESC(recur_count, " Recursion level for the stack overflow test, "\
- "default is 10");
+MODULE_PARM_DESC(recur_count, " Recursion level for the stack overflow test");
module_param(cpoint_name, charp, 0444);
MODULE_PARM_DESC(cpoint_name, " Crash Point, where kernel is to be crashed");
module_param(cpoint_type, charp, 0444);
@@ -280,16 +290,16 @@ static int lkdtm_parse_commandline(void)
return -EINVAL;
}
-static int recursive_loop(int a)
+static int recursive_loop(int remaining)
{
- char buf[1024];
+ char buf[REC_STACK_SIZE];
- memset(buf,0xFF,1024);
- recur_count--;
- if (!recur_count)
+ /* Make sure compiler does not optimize this away. */
+ memset(buf, (remaining & 0xff) | 0x1, REC_STACK_SIZE);
+ if (!remaining)
return 0;
else
- return recursive_loop(a);
+ return recursive_loop(remaining - 1);
}
static void do_nothing(void)
@@ -333,7 +343,7 @@ static void lkdtm_do_action(enum ctype which)
;
break;
case CT_OVERFLOW:
- (void) recursive_loop(0);
+ (void) recursive_loop(recur_count);
break;
case CT_CORRUPT_STACK:
corrupt_stack();