On Tue, Dec 04, 2018 at 01:49:11PM +0000, Peter Rosin wrote:
> On 2018-12-04 13:13, Nicholas Mc Guire wrote:
> > On Tue, Dec 04, 2018 at 11:16:59AM +0000, Peter Rosin wrote:
> >> Hi!
> >>
> >> This patch looks like a good idea. However, a nitpick below.
> >>
> >> On 2018-12-01 11:01, Nicholas Mc Guire wrote:
> >>> devm_kstrdup() may return NULL if internal allocation failed.
> >>> Thus using name, value is unsafe without being checked. As
> >>> i2c_demux_pinctrl_probe() can return -ENOMEM in other cases
> >>> a dev_err() message is included to make the failure location
> >>> clear.
> >>>
> >>> Signed-off-by: Nicholas Mc Guire <hofrat@xxxxxxxxx>
> >>> Fixes: e35478eac030 ("i2c: mux: demux-pinctrl: run properly with multiple instances")
> >>> ---
> >>>
> >>> Problem located with experimental coccinelle script
> >>>
> >>> Q: The use of devm_kstrdup() seems a bit odd while technically not wrong,
> >>> personally I think devm_kasprintf() would be more suitable here.
> >>>
> >>> Patch was compile tested with: multi_v7_defconfig
> >>> (implies I2C_DEMUX_PINCTRL=y)
> >>>
> >>> Patch is against 4.20-rc4 (localversion-next is next-20181130)
> >>>
> >>> drivers/i2c/muxes/i2c-demux-pinctrl.c | 6 ++++++
> >>> 1 file changed, 6 insertions(+)
> >>>
> >>> diff --git a/drivers/i2c/muxes/i2c-demux-pinctrl.c b/drivers/i2c/muxes/i2c-demux-pinctrl.c
> >>> index 035032e..c466999 100644
> >>> --- a/drivers/i2c/muxes/i2c-demux-pinctrl.c
> >>> +++ b/drivers/i2c/muxes/i2c-demux-pinctrl.c
> >>> @@ -244,6 +244,12 @@ static int i2c_demux_pinctrl_probe(struct platform_device *pdev)
> >>>
> >>> props[i].name = devm_kstrdup(&pdev->dev, "status", GFP_KERNEL);
> >>> props[i].value = devm_kstrdup(&pdev->dev, "ok", GFP_KERNEL);
> >>> + if (!props[i].name || !props[i].value) {
> >>> + dev_err(&pdev->dev,
> >>> + "chan %d name, value allocation failed\n", i);
> >>
> >> Please drop this memory allocation failure message. You should get such a
> >> message from devm_kstrdup.
> >>
> >
> > hm...tried to figure out where that message would be comming
> > from - but I could not find any point in the call tree that
> > would issue such a message ?
> >
> > devm_kstrdup()
> > -> devm_kmalloc()
> > -> alloc_dr()
> > --> kmalloc_track_caller() (non-NUMA)
> > | -> __kmalloc_node()
> > | -> __do_kmalloc_node()
> > `-> __kmalloc_node_track_caller() (NUMA)
> > -> __do_kmalloc_node()
> >
> > __do_kmalloc_node() seems like it simply returns NULL but
> > issues no failure message.
> > Am I overlooking something ?
>
> Well, I don't know the details, but checkpatch will warn about simple
> error messages on devm_kstrdup failure (if I read the checkpatch source
> correctly). But in this case there are two parallel conditions in the
> if and hence checkpatch stumbles, but gist is the same, you should not
> sprinkle messages on memory allocation failure.
>
not in this case - atleast checkpatch --strict on the original patch
did not issue any complaint to that ends. But yes - you
are right that the intent in checkpatch is clear and this should not
be carrying a failure message.
thx!
hofrat
