drm/msm: Fix pgtable prealloc error path

Summary

In the Linux kernel, the following vulnerability has been resolved: drm/msm: Fix pgtable prealloc error path The following splat was reported: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010 Mem abort info: ESR = 0x0000000096000004 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x04: level 0 translation fault Data abort info: ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 user pgtable: 4k pages, 48-bit VAs, pgdp=00000008d0fd8000 [0000000000000010] pgd=0000000000000000, p4d=0000000000000000 Internal error: Oops: 0000000096000004 [#1] SMP CPU: 5 UID: 1000 PID: 149076 Comm: Xwayland Tainted: G S 6.16.0-rc2-00809-g0b6974bb4134-dirty #367 PREEMPT Tainted: [S]=CPU_OUT_OF_SPEC Hardware name: Qualcomm Technologies, Inc. SM8650 HDK (DT) pstate: 83400005 (Nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--) pc : build_detached_freelist+0x28/0x224 lr : kmem_cache_free_bulk.part.0+0x38/0x244 sp : ffff000a508c7a20 x29: ffff000a508c7a20 x28: ffff000a508c7d50 x27: ffffc4e49d16f350 x26: 0000000000000058 x25: 00000000fffffffc x24: 0000000000000000 x23: ffff00098c4e1450 x22: 00000000fffffffc x21: 0000000000000000 x20: ffff000a508c7af8 x19: 0000000000000002 x18: 00000000000003e8 x17: ffff000809523850 x16: ffff000809523820 x15: 0000000000401640 x14: ffff000809371140 x13: 0000000000000130 x12: ffff0008b5711e30 x11: 00000000001058fa x10: 0000000000000a80 x9 : ffff000a508c7940 x8 : ffff000809371ba0 x7 : 781fffe033087fff x6 : 0000000000000000 x5 : ffff0008003cd000 x4 : 781fffe033083fff x3 : ffff000a508c7af8 x2 : fffffdffc0000000 x1 : 0001000000000000 x0 : ffff0008001a6a00 Call trace: build_detached_freelist+0x28/0x224 (P) kmem_cache_free_bulk.part.0+0x38/0x244 kmem_cache_free_bulk+0x10/0x1c msm_iommu_pagetable_prealloc_cleanup+0x3c/0xd0 msm_vma_job_free+0x30/0x240 msm_ioctl_vm_bind+0x1d0/0x9a0 drm_ioctl_kernel+0x84/0x104 drm_ioctl+0x358/0x4d4 __arm64_sys_ioctl+0x8c/0xe0 invoke_syscall+0x44/0x100 el0_svc_common.constprop.0+0x3c/0xe0 do_el0_svc+0x18/0x20 el0_svc+0x30/0x100 el0t_64_sync_handler+0x104/0x130 el0t_64_sync+0x170/0x174 Code: aa0203f5 b26287e2 f2dfbfe2 aa0303f4 (f8737ab6) ---[ end trace 0000000000000000 ]--- Since msm_vma_job_free() is called directly from the ioctl, this looks like an error path cleanup issue. Which I think results from prealloc_cleanup() called without a preceding successful prealloc_allocate() call. So handle that case better. Patchwork: https://patchwork.freedesktop.org/patch/678677/