> On 28 Apr 2022, at 11:51, Christophe Marie Francois Dupont de Dinechin > <[email protected]> wrote: > > > >> On 28 Apr 2022, at 11:46, Christophe Marie Francois Dupont de Dinechin >> <[email protected]> wrote: >> >> >> >>> On 15 Apr 2022, at 05:51, Murilo Opsfelder Araújo <[email protected]> >>> wrote: >>> >>> On 4/14/22 23:30, Murilo Opsfelder Araujo wrote: >>>> GCC 12 enhanced -Waddress when comparing array address to null [0], >>>> which warns: >>>> drivers/virtio/virtio_pci_common.c: In function ‘vp_del_vqs’: >>>> drivers/virtio/virtio_pci_common.c:257:29: warning: the comparison will >>>> always evaluate as ‘true’ for the pointer operand in >>>> ‘vp_dev->msix_affinity_masks + (sizetype)((long unsigned int)i * 256)’ >>>> must not be NULL [-Waddress] >>>> 257 | if (vp_dev->msix_affinity_masks[i]) >>>> | ^~~~~~ >>>> In fact, the verification is comparing the result of a pointer >>>> arithmetic, the address "msix_affinity_masks + i", which will always >>>> evaluate to true. >>>> Under the hood, free_cpumask_var() calls kfree(), which is safe to pass >>>> NULL, not requiring non-null verification. So remove the verification >>>> to make compiler happy (happy compiler, happy life). >>>> [0] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102103 >>>> Signed-off-by: Murilo Opsfelder Araujo <[email protected]> >>>> --- >>>> drivers/virtio/virtio_pci_common.c | 3 +-- >>>> 1 file changed, 1 insertion(+), 2 deletions(-) >>>> diff --git a/drivers/virtio/virtio_pci_common.c >>>> b/drivers/virtio/virtio_pci_common.c >>>> index d724f676608b..5046efcffb4c 100644 >>>> --- a/drivers/virtio/virtio_pci_common.c >>>> +++ b/drivers/virtio/virtio_pci_common.c >>>> @@ -254,8 +254,7 @@ void vp_del_vqs(struct virtio_device *vdev) >>>> if (vp_dev->msix_affinity_masks) { >>>> for (i = 0; i < vp_dev->msix_vectors; i++) >>>> - if (vp_dev->msix_affinity_masks[i]) >>>> - >>>> free_cpumask_var(vp_dev->msix_affinity_masks[i]); >>>> + free_cpumask_var(vp_dev->msix_affinity_masks[i]); >>>> } >>>> if (vp_dev->msix_enabled) { >>> >>> After I sent this message, I realized that Christophe (copied here) >>> had already proposed a fix: >>> >>> https://lore.kernel.org/lkml/[email protected]/ >>> >>> Christophe, >>> >>> Since free_cpumask_var() calls kfree() and kfree() is null-safe, >>> can we just drop this null verification and call free_cpumask_var() right >>> away? >> >> Apologies for the delay in responding, broken laptop… >> >> In the case where CONFIG_CPUMASK_OFFSTACK is not defined, we have: >> >> typedef struct cpumask cpumask_var_t[1]; >> >> So that vp_dev->msix_affinity_masks[i] is statically not null (that’s the >> warning) >> but also a static pointer, so not kfree-safe IMO. > > … which also renders my own patch invalid :-/ > > Compiler warnings are good. Clearly not sufficient.
Ah, I just noticed that free_cpumask_var is a noop in that case. So yes, your fix is better :-) _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
