Fix for realloc bug and wrong error logging

This patch fixes two bugs in blktrace.

1. realloc is called on a wrong memory address (glibc reports heap
corruption if the user sends the output to a pipe, for example "blktrace
/dev/sdc -o -").

2. errno 0 is actually reported if debugfs is not mounted

Mikulas

Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 7 insertions, 2 deletions

diff --git a/blktrace.c b/blktrace.c
index 72866e2..b14daf2 100644
--- a/blktrace.c
+++ b/blktrace.c
@@ -1330,7 +1330,7 @@ static struct trace_buf *tb_combine(struct trace_buf *prev,
 		 * the whole structures, as the other fields
 		 * are "static".
 		 */
-		prev = realloc(prev->buf, sizeof(*prev) + tot_len);
+		prev = realloc(prev, sizeof(*prev) + tot_len);
 		prev->buf = (void *)(prev + 1);
 	}
 
@@ -2155,12 +2155,17 @@ static int handle_args(int argc, char *argv[])
 		return 1;
 	}
 
-	if (statfs(debugfs_path, &st) < 0 || st.f_type != (long)DEBUGFS_TYPE) {
+	if (statfs(debugfs_path, &st) < 0) {
 		fprintf(stderr, "Invalid debug path %s: %d/%s\n",
 			debugfs_path, errno, strerror(errno));
 		return 1;
 	}
 
+	if (st.f_type != (long)DEBUGFS_TYPE) {
+		fprintf(stderr, "Debugfs is not mounted at %s\n", debugfs_path);
+		return 1;
+	}
+
 	if (act_mask_tmp != 0)
 		act_mask = act_mask_tmp;