[PATCH] perf trace-event: Fix buffer overflow in read_string()

[Tanushree Shah <tshah@linux.ibm.com>]

read_string() writes into buf[BUFSIZ] one byte at a time without
checking 'size' against the buffer bound before each write. A
string longer than BUFSIZ in the input overflows the stack buffer.

Add a bounds check before each write to prevent overflow. On
overflow the function returns NULL, matching its other error paths.

Fixes: 9215545e99d8 ("perf: Convert perf tracing data into a tracing_data event")
Signed-off-by: Tanushree Shah <tshah@linux.ibm.com>
---
 tools/perf/util/trace-event-read.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/perf/util/trace-event-read.c b/tools/perf/util/trace-event-read.c
index ecbbb93f0185..afd458cf1387 100644
--- a/tools/perf/util/trace-event-read.c
+++ b/tools/perf/util/trace-event-read.c
@@ -127,6 +127,11 @@ static char *read_string(void)
 			}
 		}
 
+		if (size >= (int)sizeof(buf) - 1) {
+			pr_debug("string too long (max %zu bytes)", sizeof(buf) - 1);
+			goto out;
+		}
+
 		buf[size++] = c;
 
 		if (!c)
-- 
2.47.3