Re: [PATCH v6 7/9] tracing: Replace strncpy() with strscpy()
From: Justin Stitt <justinstitt@google.com>
Date: 2024-08-13 22:19:29
Also in:
bpf, dri-devel, linux-fsdevel, linux-mm, linux-security-module, netdev, selinux
Hi, On Mon, Aug 12, 2024 at 10:29:31AM GMT, Yafang Shao wrote:
Using strscpy() to read the task comm ensures that the name is always NUL-terminated, regardless of the source string. This approach also facilitates future extensions to the task comm.
Thanks for sending patches replacing str{n}cpy's!
I believe there's at least two more instances of strncpy in trace.c as
well as in trace_events_hist.c (for a grand total of 6 instances in the
files you've touched in this specific patch).
It'd be great if you could replace those instances in this patch as well :>)
This would help greatly with [1].
quoted hunk ↗ jump to hunk
Signed-off-by: Yafang Shao <redacted> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> --- kernel/trace/trace.c | 2 +- kernel/trace/trace_events_hist.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 578a49ff5c32..1b2577f9d734 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c@@ -1907,7 +1907,7 @@ __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; - strncpy(max_data->comm, tsk->comm, TASK_COMM_LEN); + strscpy(max_data->comm, tsk->comm, TASK_COMM_LEN);
If max_data->comm wants to be NUL-terminated then this is the right replacement. Without knowing how the trace stack works at all, it's hard for me to tell if that is the case. There's a length-supplied format specifier for which this comm field is used with; Either this is just another safeguard against spilling over the buffer or this field really doesn't care about NUL-termination. | seq_printf(m, "# | task: %.16s-%d " | "(uid:%d nice:%ld policy:%ld rt_prio:%ld)\n", | data->comm, data->pid, In the event this field doesn't need to be NUL-terminated then we are introducing an off-by-one error where we are copying one less useful byte with strscpy -- Linus pointed out earlier [2] that these things all just want to be c-strings so this is probably the right change :>)
quoted hunk ↗ jump to hunk
max_data->pid = tsk->pid; /* * If tsk == current, then use current_uid(), as that does not usediff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 6ece1308d36a..4cd24c25ce05 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c@@ -1599,7 +1599,7 @@ static inline void save_comm(char *comm, struct task_struct *task) return; } - strncpy(comm, task->comm, TASK_COMM_LEN); + strscpy(comm, task->comm, TASK_COMM_LEN); } static void hist_elt_data_free(struct hist_elt_data *elt_data)-- 2.43.5
Link: https://github.com/KSPP/linux/issues/90 [1] Link: https://lore.kernel.org/all/CAHk-=whWtUC-AjmGJveAETKOMeMFSTwKwu99v7+b6AyHMmaDFA@mail.gmail.com/ (local) [2] Thanks Justin