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+
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