On Tue, Dec 5, 2017 at 7:20 AM, Arnd Bergmann <a...@arndb.de> wrote: > While reviewing all callers of get_task_comm(), I stumbled > over this one that claimed it was not exported, when in fact > it is. Accessing task->comm directly is not safe, so better > convert this one to using get_task_comm as well.
Using get_task_comm() in cases like this is actually overkill (i.e. using up stack space), since there's (currently) no benefit. Nothing protects getting a "correct" view of task->comm (i.e. it could get updated in the middle of a copy), but it _is_ always NULL terminated, so it's safe to use with %s like this. While it does make me slightly uncomfortable to _depend_ on this NULL termination, but there are lots of open-coded %s users of task->comm. When we're trying to save a _copy_ of task->comm, then we want get_task_comm(), just to make sure we're doing it right. So, while I don't oppose this patch, it might be seen as a wasteful use of stack space. -Kees > > Signed-off-by: Arnd Bergmann <a...@arndb.de> > --- > fs/ocfs2/cluster/netdebug.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/fs/ocfs2/cluster/netdebug.c b/fs/ocfs2/cluster/netdebug.c > index 74a21f6695c8..a51d001b89b1 100644 > --- a/fs/ocfs2/cluster/netdebug.c > +++ b/fs/ocfs2/cluster/netdebug.c > @@ -130,6 +130,7 @@ static void *nst_seq_next(struct seq_file *seq, void *v, > loff_t *pos) > static int nst_seq_show(struct seq_file *seq, void *v) > { > struct o2net_send_tracking *nst, *dummy_nst = seq->private; > + char comm[TASK_COMM_LEN]; > ktime_t now; > s64 sock, send, status; > > @@ -142,8 +143,8 @@ static int nst_seq_show(struct seq_file *seq, void *v) > sock = ktime_to_us(ktime_sub(now, nst->st_sock_time)); > send = ktime_to_us(ktime_sub(now, nst->st_send_time)); > status = ktime_to_us(ktime_sub(now, nst->st_status_time)); > + get_task_comm(comm, nst->st_task); > > - /* get_task_comm isn't exported. oh well. */ > seq_printf(seq, "%p:\n" > " pid: %lu\n" > " tgid: %lu\n" > @@ -158,7 +159,7 @@ static int nst_seq_show(struct seq_file *seq, void *v) > " wait start: %lld usecs ago\n", > nst, (unsigned long)task_pid_nr(nst->st_task), > (unsigned long)nst->st_task->tgid, > - nst->st_task->comm, nst->st_node, > + comm, nst->st_node, > nst->st_sc, nst->st_id, nst->st_msg_type, > nst->st_msg_key, > (long long)sock, > -- > 2.9.0 > -- Kees Cook Pixel Security