Messages in this thread | | | From | KOSAKI Motohiro <> | Date | Sun, 7 Apr 2013 23:52:34 -0400 | Subject | Re: [PATCH] kernel: tsacct: strncpy, always be sure of NUL terminated. |
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On Sun, Apr 7, 2013 at 11:27 PM, Chen Gang <gang.chen@asianux.com> wrote: > > for NUL terminated string, always set '\0' at the end. > > Signed-off-by: Chen Gang <gang.chen@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?
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.
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