In the Linux kernel, the following vulnerability has been resolved:
powerpc/pseries/iommu: Don't unset window if it was never set
On pSeries, when user attempts to use the same vfio container used by different iommu group, the spaprtceset_window() returns -EPERM and the subsequent cleanup leads to the below crash.
Kernel attempted to read user page (308) - exploit attempt? BUG: Kernel NULL pointer dereference on read at 0x00000308 Faulting instruction address: 0xc0000000001ce358 Oops: Kernel access of bad area, sig: 11 [#1] NIP: c0000000001ce358 LR: c0000000001ce05c CTR: c00000000005add0 <snip> NIP [c0000000001ce358] spaprtceunsetwindow+0x3b8/0x510 LR [c0000000001ce05c] spaprtceunsetwindow+0xbc/0x510 Call Trace: spaprtceunsetwindow+0xbc/0x510 (unreliable) tceiommuattachgroup+0x24c/0x340 [vfioiommuspaprtce] vfiocontainerattachgroup+0xec/0x240 [vfio] vfiogroupfopsunlioctl+0x548/0xb00 [vfio] sysioctl+0x754/0x1580 systemcallexception+0x13c/0x330 systemcallvectoredcommon+0x15c/0x2ec <snip> --- interrupt: 3000
Fix this by having null check for the tbl passed to the spaprtceunset_window().