[for-next][PATCH 2/2] tracing: Use strncpy instead of memcpy when copying comm in trace.c

From: Steven Rostedt
Date: Wed Mar 06 2019 - 05:17:32 EST

From: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>

Because there may be random garbage beyond a string's null terminator,
code that might use the entire comm array e.g. histogram keys, can
give unexpected results if that garbage is copied in too, so avoid
that possibility by using strncpy instead of memcpy.

Link: http://lkml.kernel.org/r/1d6ebac26570c2a29ce9fb575379f17ef5c8b81b.1551802084.git.tom.zanussi@xxxxxxxxxxxxxxx

Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
Suggested-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
kernel/trace/trace.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 3835f7ed3293..e9cc47e59d25 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1497,7 +1497,7 @@ __update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
max_data->critical_start = data->critical_start;
max_data->critical_end = data->critical_end;

- memcpy(max_data->comm, tsk->comm, TASK_COMM_LEN);
+ strncpy(max_data->comm, tsk->comm, TASK_COMM_LEN);
max_data->pid = tsk->pid;
* If tsk == current, then use current_uid(), as that does not use
@@ -1923,7 +1923,7 @@ static inline char *get_saved_cmdlines(int idx)

static inline void set_cmdline(int idx, const char *cmdline)
- memcpy(get_saved_cmdlines(idx), cmdline, TASK_COMM_LEN);
+ strncpy(get_saved_cmdlines(idx), cmdline, TASK_COMM_LEN);

static int allocate_cmdlines_buffer(unsigned int val,