UBUNTU-CVE-2026-90429: Use After Free

In the Linux kernel, the following vulnerability has been resolved: iommu/tegra241-cmdqv: Synchronize the error ISR against VINTF (de)init A user VINTF is torn down by tegra241cmdqvdeinitvintf(), which runs from the destroy callback and from the init-failure unwind in the alloc handler. It clears the cmdqv->vintfs[] slot and lets the iommufd core free it, but nothing serializes that against the error interrupt: tegra241cmdqvisr() reads cmdqv->vintfs[idx] and dereferences the vintf. A concurrent error can make the ISR read a slot mid-clear (a NULL deref) or use a vintf which is about to be freed (a use-after-free). deinitvintf() also returns idx to the IDA before clearing the slot, so a concurrent create that reuses idx can publish its new vintf into the slot, only for this teardown to erase it again with the stale NULL store. On the other end, tegra241cmdqvinitvintf() publishes a new vintf with a plain store to the cmdqv->vintfs[] slot, and the ISR dereferences fields of a published vintf such as vintf->base. A plain store gives no ordering on a weakly-ordered CPU, and a stale VINTFERRMAP bit on a reused idx can make the ISR pick a vintf the moment it is published, before its fields are set or tegra241vintfhwinit() runs. The cmdqv->vintfs[0] slot stays NULL until tegra241cmdqvinitstructures() first creates VINTF0, so the slot 0 read needs the same NULL check. Publish every slot with an smpstorerelease(), and read each slot in the ISR with an smploadacquire() under a NULL check, so the ISR always sees a fully built vintf or NULL. Also make deinitvintf() clear the slot, and synchronizeirq() prior to returning idx to the IDA, so no vintf is freed under a running handler and no reused idx is clobbered.