On Sat, Jan 11, 2014 at 12:59 AM, Andrew Morton
<a...@linux-foundation.org> wrote:
>> +char *comm_name(char *buf, char *end, struct task_struct *tsk,
>> + struct printf_spec spec, const char *fmt)
>> +{
>> + char name[TASK_COMM_LEN];
>> +
>> + /* Caller can pass NULL instead of current. */
>> + if (!tsk)
>> + tsk = current;
>> + /* Not using get_task_comm() in case I'm in IRQ context. */
>> + memcpy(name, tsk->comm, TASK_COMM_LEN);
So this may copy more bytes than the actual string length of tsk->comm.
As this is a temporary buffer, that just wastes cycles.
And even if it wasn't, data between the string zero terminator and the end of
the buffer wouild be leaked.
>> + name[sizeof(name) - 1] = '\0';
You can use strlcpy() here instead of memcpy and clear.
> get_task_comm() uses strncpy()?
char *get_task_comm(char *buf, struct task_struct *tsk)
{
/* buf must be at least sizeof(tsk->comm) in size */
task_lock(tsk);
strncpy(buf, tsk->comm, sizeof(tsk->comm));
task_unlock(tsk);
return buf;
}
Is get_task_comm() used to prepare data for userspace?
strncpy() fills the remaining of the buffer with zeroes, so it avoids leaking
data.
Note that strncpy() may leave the buffer non-zero-terminated if the source
string is too long, but as set_task_comm() uses strlcpy(), this should never
be the case:
void set_task_comm(struct task_struct *tsk, char *buf)
{
task_lock(tsk);
trace_task_rename(tsk, buf);
strlcpy(tsk->comm, buf, sizeof(tsk->comm));
task_unlock(tsk);
perf_event_comm(tsk);
}
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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