drm/nouveau/mmu: ALIGN_DOWN correct variable

Commit 7110c89bb8852ff8b0f88ce05b332b3fe22bd11e ("mmu: swap out round
for ALIGN") replaced two calls to round/rounddown with ALIGN/ALIGN_DOWN,
but erroneously applied ALIGN_DOWN to a different variable (addr) and left
intended variable (tail) not rounded/ALIGNed.

As a result screen corruption, X lockups are observable. An example of kernel
log of affected system with NV98 card where it was bisected:

nouveau 0000:01:00.0: gr: TRAP_M2MF 00000002 [IN]
nouveau 0000:01:00.0: gr: TRAP_M2MF 00320951 400007c0 00000000 04000000
nouveau 0000:01:00.0: gr: 00200000 [] ch 1 [000fbbe000 DRM] subc 4 class 5039
mthd 0100 data 00000000
nouveau 0000:01:00.0: fb: trapped read at 0040000000 on channel 1
[0fbbe000 DRM]
engine 00 [PGRAPH] client 03 [DISPATCH] subclient 04 [M2M_IN] reason 00000006
[NULL_DMAOBJ]

Fixes bug 105173 ("[MCP79][Regression] Unhandled NULL pointer dereference in
nvkm_object_unmap since kernel 4.15")
https://bugs.freedesktop.org/show_bug.cgi?id=105173

Fixes: 7110c89bb885 ("mmu: swap out round for ALIGN ")
Tested-by: Pierre Moreau <pierre.morrow@free.fr>
Reviewed-by: Pierre Moreau <pierre.morrow@free.fr>
Signed-off-by: Maris Nartiss <maris.nartiss@gmail.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Cc: stable@vger.kernel.org # v4.15+

diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.c b/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.c
index 93946dcee3191be1418ecf332ef7135854849a09..1c12e58f44c2684b5ce0d84a18e286b55a01235f 100644 (file)
--- a/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.c
+++ b/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.c
@@ -1354,7 +1354,7 @@ nvkm_vmm_get_locked(struct nvkm_vmm *vmm, bool getref, bool mapref, bool sparse,
 
                tail = this->addr + this->size;
                if (vmm->func->page_block && next && next->page != p)
-                       tail = ALIGN_DOWN(addr, vmm->func->page_block);
+                       tail = ALIGN_DOWN(tail, vmm->func->page_block);
 
                if (addr <= tail && tail - addr >= size) {
                        rb_erase(&this->tree, &vmm->free);