drm/nouveau: fix off by one in BIOS boundary checking

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

diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/bios/base.c b/drivers/gpu/drm/nouveau/nvkm/subdev/bios/base.c
index d0f52d59fc2f9f6eef9ef79e123ace125c9e1bc4..64e423dddd9e7fe01209838e391a7e4761a6183c 100644 (file)
--- 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;
        }