[PATCH v2] drm/nouveau: fix div-by-zero in nouveau_bo_fixup_align

[Alexey Simakov <bigalex934@gmail.com>]

The expression 64 * nvbo->mode can be zero when nvbo->mode equals
U32_MAX / 64, causing a division by zero in do_div(). Values greater
than U32_MAX / 64 cause a u32 overflow, leading to incorrect results.

Since nvbo->mode comes from userspace via ioctl, it must be validated
to prevent crashes or undefined behavior.

Add a check to ensure nvbo->mode is less than U32_MAX / 64
before use in multiplication.

Found by Linux Verification Center (linuxtesting.org) with Svace.

Fixes: a0af9add499c ("drm/nouveau: Make the MM aware of pre-G80 tiling.")
Co-developed-by: Alexandr Sapozhnikov <alsp705@gmail.com>
Signed-off-by: Alexandr Sapozhnikov <alsp705@gmail.com>
Signed-off-by: Alexey Simakov <bigalex934@gmail.com>
---
 drivers/gpu/drm/nouveau/nouveau_bo.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
index 96a8b7b1215e..774888ffa4a8 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bo.c
+++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
@@ -207,6 +207,9 @@ nouveau_bo_alloc(struct nouveau_cli *cli, u64 *size, int *align, u32 domain,
 	struct nvif_vmm *vmm = cli->svm.cli ? &cli->svm.vmm : &cli->vmm.vmm;
 	int i, pi = -1;
 
+	if (tile_mode > U32_MAX / 64)
+		return ERR_PTR(-EINVAL);
+
 	if (!*size) {
 		NV_WARN(drm, "skipped size %016llx\n", *size);
 		return ERR_PTR(-EINVAL);
-- 
2.34.1