> On 28 Apr 2022, at 11:46, Christophe Marie Francois Dupont de Dinechin <cdupontd@xxxxxxxxxx> wrote: > > > >> 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. … which also renders my own patch invalid :-/ Compiler warnings are good. Clearly not sufficient. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
