On 2013年04月08日 11:52, KOSAKI Motohiro wrote:
> On Sun, Apr 7, 2013 at 11:27 PM, Chen Gang <gang.c...@asianux.com> wrote:
>> >
>> > for NUL terminated string, always set '\0' at the end.
>> >
>> > Signed-off-by: Chen Gang <gang.c...@asianux.com>
>> > ---
>> > kernel/tsacct.c | 3 ++-
>> > 1 files changed, 2 insertions(+), 1 deletions(-)
>> >
>> > diff --git a/kernel/tsacct.c b/kernel/tsacct.c
>> > index a1dd9a1..01bcc4e 100644
>> > --- a/kernel/tsacct.c
>> > +++ b/kernel/tsacct.c
>> > @@ -78,7 +78,8 @@ void bacct_add_tsk(struct user_namespace *user_ns,
>> > stats->ac_minflt = tsk->min_flt;
>> > stats->ac_majflt = tsk->maj_flt;
>> >
>> > - strncpy(stats->ac_comm, tsk->comm, sizeof(stats->ac_comm));
>> > + strncpy(stats->ac_comm, tsk->comm, sizeof(stats->ac_comm) - 1);
>> > + stats->ac_comm[sizeof(stats->ac_comm) - 1] = '\0';
> sizeof(tsk->comm) is 16 and sizeof(stats->ac_comm) is 32. then this statement
> is strange. and set_task_comm ensure tsk->comm is nul-terminated.
>
> so your code never change the behavior, right?
>
right.
thank you for your information:
originally, I really did not check the sizeof details.
> And, If buggy driver change tsk->comm not to use set_task_comm and tsk->comm
> is not nul-terminated, strncpy() still touch unrelated memory and ac_comm may
> expose kernel internal info. that's bad.
>
>
really, that's bad !
thank you for your information:
originally, I did not think of a buggy driver can change tsk->comm.
:-)
--
Chen Gang
Asianux Corporation
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