> On 15 Apr 2022, at 05:51, Murilo Opsfelder Araújo <muriloo@xxxxxxxxxxxxx> 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 <muriloo@xxxxxxxxxxxxx> >> --- >> 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/20220414150855.2407137-4-dinechin@xxxxxxxxxx/ > > 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. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
