[LTP] [PATCH v2] genload: fix memory corruption in hogvm()

[Jiwei Sun]

From: Jiwei Sun <sunjw10@lenovo.com>

When running memory stress test with the following commands,

  # ./genload -v --vm 10 --vm-chunks 4 --vm-bytes 1073741824

or

  # ./genload -v --vm 10 --vm-chunks 0 --vm-bytes 1073741824

The following error log will be shown,

  malloc(): corrupted top size

The root cause of the issue is that allocated memory for ptr is less
than what is actually needed.

Reviewed-by: Adrian Huang <ahuang12@lenovo.com>
Signed-off-by: Jiwei Sun <sunjw10@lenovo.com>
---
v2 changes:
 - Delete excess "* 2" when allocate memory for ptr
 - Adjust "chunks" from 0 to 1

 tools/genload/genload.c | 15 ++++++++++-----
 tools/genload/stress.c  | 15 ++++++++++-----
 2 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/tools/genload/genload.c b/tools/genload/genload.c
index 7f56d5272..a19d519fd 100644
--- a/tools/genload/genload.c
+++ b/tools/genload/genload.c
@@ -641,9 +641,16 @@ int hogvm(long long forks, long long chunks, long long bytes)
 			/* Use a backoff sleep to ensure we get good fork throughput.  */
 			usleep(backoff);
 
+			/* If chunks is 0, ptr will allocate 0 bytes's
+			 * memory, it will cause the process to crash
+			 * during runtime, so adjust to 1 */
+			if (chunks == 0)
+				chunks = 1;
+
 			while (1) {
-				ptr = (char **)malloc(chunks * 2);
-				for (j = 0; chunks == 0 || j < chunks; j++) {
+				ptr = (char **)malloc(chunks *
+						sizeof(char *));
+				for (j = 0; j < chunks; j++) {
 					if ((ptr[j] =
 					     (char *)malloc(bytes *
 							    sizeof(char)))) {
@@ -674,10 +681,8 @@ int hogvm(long long forks, long long chunks, long long bytes)
 				if (retval == 0) {
 					dbg(stdout,
 					    "hogvm worker freeing memory and starting over\n");
-					for (j = 0; chunks == 0 || j < chunks;
-					     j++) {
+					for (j = 0; j < chunks; j++)
 						free(ptr[j]);
-					}
 					free(ptr);
 					continue;
 				}
diff --git a/tools/genload/stress.c b/tools/genload/stress.c
index 7f56d5272..a19d519fd 100644
--- a/tools/genload/stress.c
+++ b/tools/genload/stress.c
@@ -641,9 +641,16 @@ int hogvm(long long forks, long long chunks, long long bytes)
 			/* Use a backoff sleep to ensure we get good fork throughput.  */
 			usleep(backoff);
 
+			/* If chunks is 0, ptr will allocate 0 bytes's
+			 * memory, it will cause the process to crash
+			 * during runtime, so adjust to 1 */
+			if (chunks == 0)
+				chunks = 1;
+
 			while (1) {
-				ptr = (char **)malloc(chunks * 2);
-				for (j = 0; chunks == 0 || j < chunks; j++) {
+				ptr = (char **)malloc(chunks *
+						sizeof(char *));
+				for (j = 0; j < chunks; j++) {
 					if ((ptr[j] =
 					     (char *)malloc(bytes *
 							    sizeof(char)))) {
@@ -674,10 +681,8 @@ int hogvm(long long forks, long long chunks, long long bytes)
 				if (retval == 0) {
 					dbg(stdout,
 					    "hogvm worker freeing memory and starting over\n");
-					for (j = 0; chunks == 0 || j < chunks;
-					     j++) {
+					for (j = 0; j < chunks; j++)
 						free(ptr[j]);
-					}
 					free(ptr);
 					continue;
 				}
-- 
2.27.0