| Message ID | 20180205140852.14110-1-colin.king@canonical.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Feb 05, 2018 at 02:08:52PM +0000, Colin King wrote: > From: Colin Ian King <colin.king@canonical.com> > > Pointer dev is being assigned a value that is never read, it is being > re-assigned the same value later on, hence the initialization is redundant > and can be removed. > > Cleans up clang warning: > drivers/nvdimm/pfn_devs.c:307:17: warning: Value stored to 'dev' during > its initialization is never read > > Signed-off-by: Colin Ian King <colin.king@canonical.com> Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com> More importantly this fixes a potential NULL pointer dereference. nd_pfn is checked for NULL a few lines down, but we would have crashed here trying to get nd_pfn->dev. We can append the above info to the changelog when we apply. > --- > drivers/nvdimm/pfn_devs.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c > index f5c4e8c6e29d..2f4d18752c97 100644 > --- a/drivers/nvdimm/pfn_devs.c > +++ b/drivers/nvdimm/pfn_devs.c > @@ -304,7 +304,7 @@ static const struct attribute_group *nd_pfn_attribute_groups[] = { > struct device *nd_pfn_devinit(struct nd_pfn *nd_pfn, > struct nd_namespace_common *ndns) > { > - struct device *dev = &nd_pfn->dev; > + struct device *dev; > > if (!nd_pfn) > return NULL; > -- > 2.15.1 > > _______________________________________________ > Linux-nvdimm mailing list > Linux-nvdimm@lists.01.org > https://lists.01.org/mailman/listinfo/linux-nvdimm
On Mon, Feb 5, 2018 at 10:20 AM, Ross Zwisler <ross.zwisler@linux.intel.com> wrote: > On Mon, Feb 05, 2018 at 02:08:52PM +0000, Colin King wrote: >> From: Colin Ian King <colin.king@canonical.com> >> >> Pointer dev is being assigned a value that is never read, it is being >> re-assigned the same value later on, hence the initialization is redundant >> and can be removed. >> >> Cleans up clang warning: >> drivers/nvdimm/pfn_devs.c:307:17: warning: Value stored to 'dev' during >> its initialization is never read >> >> Signed-off-by: Colin Ian King <colin.king@canonical.com> > > Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com> > > More importantly this fixes a potential NULL pointer dereference. nd_pfn > is checked for NULL a few lines down, but we would have crashed here trying to > get nd_pfn->dev. > No we wouldn't crash. We're just calculating the address, not de-referencing a NULL pointer.
On 05/02/18 18:44, Dan Williams wrote: > On Mon, Feb 5, 2018 at 10:20 AM, Ross Zwisler > <ross.zwisler@linux.intel.com> wrote: >> On Mon, Feb 05, 2018 at 02:08:52PM +0000, Colin King wrote: >>> From: Colin Ian King <colin.king@canonical.com> >>> >>> Pointer dev is being assigned a value that is never read, it is being >>> re-assigned the same value later on, hence the initialization is redundant >>> and can be removed. >>> >>> Cleans up clang warning: >>> drivers/nvdimm/pfn_devs.c:307:17: warning: Value stored to 'dev' during >>> its initialization is never read >>> >>> Signed-off-by: Colin Ian King <colin.king@canonical.com> >> >> Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com> >> >> More importantly this fixes a potential NULL pointer dereference. nd_pfn >> is checked for NULL a few lines down, but we would have crashed here trying to >> get nd_pfn->dev. >> > > No we wouldn't crash. We're just calculating the address, not > de-referencing a NULL pointer. Indeed, it's just a warning clean up. Nothing more. > -- > To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >
On Mon, Feb 05, 2018 at 10:44:07AM -0800, Dan Williams wrote: > On Mon, Feb 5, 2018 at 10:20 AM, Ross Zwisler > <ross.zwisler@linux.intel.com> wrote: > > On Mon, Feb 05, 2018 at 02:08:52PM +0000, Colin King wrote: > >> From: Colin Ian King <colin.king@canonical.com> > >> > >> Pointer dev is being assigned a value that is never read, it is being > >> re-assigned the same value later on, hence the initialization is redundant > >> and can be removed. > >> > >> Cleans up clang warning: > >> drivers/nvdimm/pfn_devs.c:307:17: warning: Value stored to 'dev' during > >> its initialization is never read > >> > >> Signed-off-by: Colin Ian King <colin.king@canonical.com> > > > > Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com> > > > > More importantly this fixes a potential NULL pointer dereference. nd_pfn > > is checked for NULL a few lines down, but we would have crashed here trying to > > get nd_pfn->dev. > > > > No we wouldn't crash. We're just calculating the address, not > de-referencing a NULL pointer. Ah, yep, you're right of course. This is exactly how offsetof() is implemented in some architectures. Thanks.
diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c index f5c4e8c6e29d..2f4d18752c97 100644 --- a/drivers/nvdimm/pfn_devs.c +++ b/drivers/nvdimm/pfn_devs.c @@ -304,7 +304,7 @@ static const struct attribute_group *nd_pfn_attribute_groups[] = { struct device *nd_pfn_devinit(struct nd_pfn *nd_pfn, struct nd_namespace_common *ndns) { - struct device *dev = &nd_pfn->dev; + struct device *dev; if (!nd_pfn) return NULL;