From 1b777d4d9e383d2744fc9b3a09af6ec1893c8b1a Mon Sep 17 00:00:00 2001
From: Nick Lopez <github@glowingmonkey.org>
Date: Sat, 22 Jan 2022 01:19:06 -0700
Subject: [PATCH] drm/nouveau: fix off by one in BIOS boundary checking
Git-commit: 1b777d4d9e383d2744fc9b3a09af6ec1893c8b1a
Patch-mainline: v5.17-rc3
References: git-fixes

Bounds checking when parsing init scripts embedded in the BIOS reject
access to the last byte. This causes driver initialization to fail on
Apple eMac's with GeForce 2 MX GPUs, leaving the system with no working
console.

This is probably only seen on OpenFirmware machines like PowerPC Macs
because the BIOS image provided by OF is only the used parts of the ROM,
not a power-of-two blocks read from PCI directly so PCs always have
empty bytes at the end that are never accessed.

Signed-off-by: Nick Lopez <github@glowingmonkey.org>
Fixes: 4d4e9907ff572 ("drm/nouveau/bios: guard against out-of-bounds accesses to image")
Cc: <stable@vger.kernel.org> # v4.10+
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220122081906.2633061-1-github@glowingmonkey.org
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/nouveau/nvkm/subdev/bios/base.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/bios/base.c b/drivers/gpu/drm/nouveau/nvkm/subdev/bios/base.c
index d0f52d59fc2f..64e423dddd9e 100644
--- a/drivers/gpu/drm/nouveau/nvkm/subdev/bios/base.c
+++ b/drivers/gpu/drm/nouveau/nvkm/subdev/bios/base.c
@@ -38,7 +38,7 @@ nvbios_addr(struct nvkm_bios *bios, u32 *addr, u8 size)
 		*addr += bios->imaged_addr;
 	}
 
-	if (unlikely(*addr + size >= bios->size)) {
+	if (unlikely(*addr + size > bios->size)) {
 		nvkm_error(&bios->subdev, "OOB %d %08x %08x\n", size, p, *addr);
 		return false;
 	}
-- 
2.31.1