[PATCH] telemetry: avoid truncation of strlcpy return before check

[David Marchand]

On Tue, Aug 8, 2023 at 8:35 PM Bruce Richardson
<bruce.richardson at intel.com> wrote:
>
> On Tue, Aug 08, 2023 at 10:59:37AM -0700, Tyler Retzlaff wrote:
> > On Tue, Aug 08, 2023 at 10:24:41AM +0800, lihuisong (C) wrote:
> > >
> > > 在 2023/8/3 5:21, Tyler Retzlaff 写道:
> > > >strlcpy returns type size_t when directly assigning to
> > > >struct rte_tel_data data_len field it may be truncated leading to
> > > >compromised length check that follows
> > > >
> > > >Since the limit in the check is < UINT_MAX the value returned is
> > > >safe to be cast to unsigned int (which may be narrower than size_t)
> > > >but only after being checked against RTE_TEL_MAX_SINGLE_STRING_LEN
> > > >
> > > >Signed-off-by: Tyler Retzlaff <roretzla at linux.microsoft.com>
> > > >---
> > > >  lib/telemetry/telemetry_data.c | 5 +++--
> > > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > > >
> > > >diff --git a/lib/telemetry/telemetry_data.c b/lib/telemetry/telemetry_data.c
> > > >index 3b1a240..52307cb 100644
> > > >--- a/lib/telemetry/telemetry_data.c
> > > >+++ b/lib/telemetry/telemetry_data.c
> > > >@@ -41,12 +41,13 @@
> > > >  int
> > > >  rte_tel_data_string(struct rte_tel_data *d, const char *str)
> > > >  {
> > > >+  const size_t len = strlcpy(d->data.str, str, sizeof(d->data.str));
> > > sizeof(d->data.str) is equal to RTE_TEL_MAX_SINGLE_STRING_LEN(8192).
> > > So It seems that this truncation probably will not happen.
> >
> > agreed, regardless the data type choices permit a size that exceeds the
> > range of the narrower type and the assignment results in a warning being
> > generated on some targets. that's why the truncating cast is safe to
> > add.
> >
> > none of this would be necessary if data_len had been appropriately typed
> > as size_t.  Bruce should we be changing the type instead since we are in
> > 23.11 merge window...?
> >
> I'm fine either way, to be honest.

Can we conclude?
struct rte_tel_data seems internal (at least opaque from an
application pov), so I suppose the option of changing data_len to
size_t is still on the table.

And we are missing a Fixes: tag too.

Thanks.

-- 
David Marchand