On Fri, Apr 17, 2020 at 03:28:21PM +0200, Marion & Christophe JAILLET wrote:
>
> Le 14/04/2020 à 20:34, Jason Gunthorpe a écrit :
> > On Sat, Mar 28, 2020 at 08:30:40AM +0100, Christophe JAILLET wrote:
> > > There is an off-by-one issue when checking if there is enough space in the
> > > output buffer, because we must keep some place for a final '\0'.
> > >
> > > While at it:
> > > - Use 'scnprintf' instead of 'snprintf' in order to avoid a superfluous
> > > 'strlen'
> > > - avoid some useless initializations
> > > - avoida hard coded buffer size that can be computed at built time.
> > >
> > > Fixes: a51f06e1679e ("RDMA/ocrdma: Query controller information")
> > > Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
> > > The '\0' comes from memset(..., 0, ...) in all callers.
> > > This could be also avoided if needed.
> > > drivers/infiniband/hw/ocrdma/ocrdma_stats.c | 9 ++++-----
> > > 1 file changed, 4 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/infiniband/hw/ocrdma/ocrdma_stats.c b/drivers/infiniband/hw/ocrdma/ocrdma_stats.c
> > > index 5f831e3bdbad..614a449e6b87 100644
> > > +++ b/drivers/infiniband/hw/ocrdma/ocrdma_stats.c
> > > @@ -49,13 +49,12 @@ static struct dentry *ocrdma_dbgfs_dir;
> > > static int ocrdma_add_stat(char *start, char *pcur,
> > > char *name, u64 count)
> > > {
> > > - char buff[128] = {0};
> > > - int cpy_len = 0;
> > > + char buff[128];
> > > + int cpy_len;
> > > - snprintf(buff, 128, "%s: %llu\n", name, count);
> > > - cpy_len = strlen(buff);
> > > + cpy_len = scnprintf(buff, sizeof(buff), "%s: %llu\n", name, count);
> > > - if (pcur + cpy_len > start + OCRDMA_MAX_DBGFS_MEM) {
> > > + if (pcur + cpy_len >= start + OCRDMA_MAX_DBGFS_MEM) {
> > > pr_err("%s: No space in stats buff\n", __func__);
> > > return 0;
> > > }
> > The memcpy is still kind of silly right? What about this:
> >
> > static int ocrdma_add_stat(char *start, char *pcur, char *name, u64 count)
> > {
> > size_t len = (start + OCRDMA_MAX_DBGFS_MEM) - pcur;
> > int cpy_len;
> >
> > cpy_len = snprintf(pcur, len, "%s: %llu\n", name, count);
> > if (cpy_len >= len || cpy_len < 0) {
> > pr_err("%s: No space in stats buff\n", __func__);
> > return 0;
> > }
> > return cpy_len;
> > }
> >
> > Jason
>
> It can looks useless, but I think that the goal was to make sure that we
> would not display truncated data. Each line is either complete or absent.
So it needsa *pcur = 0 in the error path?
Jason
