Nouveau - Nov 2020 - [PATCH] drm/nouveau: fix relocations applying logic and a double-free

Commit 03e0d26fcf79 ("drm/nouveau: slowpath for pushbuf ioctl")
included
a logic-bug which results in the relocations not actually getting
applied at all as the call to nouveau_gem_pushbuf_reloc_apply() is
never reached. This causes a regression with graphical corruption,
triggered when relocations need to be done (for example after a
suspend/resume cycle.)

Fix by setting *apply_relocs value only if there were more than 0
relocations.

Additionally, the never reached code had a leftover u_free() call,
which, after fixing the logic, now got called and resulted in a
double-free. Fix by removing one u_free(), moving the other
and adding check for errors.

Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Ben Skeggs <bskeggs at redhat.com>
Cc: nouveau at lists.freedesktop.org
Cc: dri-devel at lists.freedesktop.org
Signed-off-by: Matti Hamalainen <ccr at tnsp.org>
Fixes: 03e0d26fcf79 ("drm/nouveau: slowpath for pushbuf ioctl")
Link: https://gitlab.freedesktop.org/drm/nouveau/-/issues/11
---
 drivers/gpu/drm/nouveau/nouveau_gem.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c
b/drivers/gpu/drm/nouveau/nouveau_gem.c
index 549bc67feabb..c2051380d18c 100644
--- a/drivers/gpu/drm/nouveau/nouveau_gem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
@@ -558,8 +558,10 @@ nouveau_gem_pushbuf_validate(struct nouveau_channel *chan,
 			NV_PRINTK(err, cli, "validating bo list\n");
 		validate_fini(op, chan, NULL, NULL);
 		return ret;
+	} else if (ret > 0) {
+		*apply_relocs = true;
 	}
-	*apply_relocs = ret;
+
 	return 0;
 }
 
@@ -662,7 +664,6 @@ nouveau_gem_pushbuf_reloc_apply(struct nouveau_cli *cli,
 		nouveau_bo_wr32(nvbo, r->reloc_bo_offset >> 2, data);
 	}
 
-	u_free(reloc);
 	return ret;
 }
 
@@ -872,9 +873,10 @@ nouveau_gem_ioctl_pushbuf(struct drm_device *dev, void
*data,
 				break;
 			}
 		}
-		u_free(reloc);
 	}
 out_prevalid:
+	if (!IS_ERR(reloc))
+		u_free(reloc);
 	u_free(bo);
 	u_free(push);
 

base-commit: 3494d58865ad4a47611dbb427b214cc5227fa5eb
-- 
2.29.2

On Fri, Nov 20, 2020 at 4:23 PM Matti Hamalainen <ccr at tnsp.org>
wrote:
>
> Commit 03e0d26fcf79 ("drm/nouveau: slowpath for pushbuf ioctl")
included
> a logic-bug which results in the relocations not actually getting
> applied at all as the call to nouveau_gem_pushbuf_reloc_apply() is
> never reached. This causes a regression with graphical corruption,
> triggered when relocations need to be done (for example after a
> suspend/resume cycle.)
>
> Fix by setting *apply_relocs value only if there were more than 0
> relocations.
>
> Additionally, the never reached code had a leftover u_free() call,
> which, after fixing the logic, now got called and resulted in a
> double-free. Fix by removing one u_free(), moving the other
> and adding check for errors.
>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: Ben Skeggs <bskeggs at redhat.com>
> Cc: nouveau at lists.freedesktop.org
> Cc: dri-devel at lists.freedesktop.org
> Signed-off-by: Matti Hamalainen <ccr at tnsp.org>
> Fixes: 03e0d26fcf79 ("drm/nouveau: slowpath for pushbuf ioctl")
> Link: https://gitlab.freedesktop.org/drm/nouveau/-/issues/11
Link: is for the mailing list submission of the patch itself (to link
the git log to the mailing list discussions), this should be
References: or similar. Aside from this:

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

Ben, I'm assuming you'll push this through your tree.
-Daniel

> ---
>  drivers/gpu/drm/nouveau/nouveau_gem.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c
b/drivers/gpu/drm/nouveau/nouveau_gem.c
> index 549bc67feabb..c2051380d18c 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_gem.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
> @@ -558,8 +558,10 @@ nouveau_gem_pushbuf_validate(struct nouveau_channel
*chan,
>                         NV_PRINTK(err, cli, "validating bo
list\n");
>                 validate_fini(op, chan, NULL, NULL);
>                 return ret;
> +       } else if (ret > 0) {
> +               *apply_relocs = true;
>         }
> -       *apply_relocs = ret;
> +
>         return 0;
>  }
>
> @@ -662,7 +664,6 @@ nouveau_gem_pushbuf_reloc_apply(struct nouveau_cli
*cli,
>                 nouveau_bo_wr32(nvbo, r->reloc_bo_offset >> 2,
data);
>         }
>
> -       u_free(reloc);
>         return ret;
>  }
>
> @@ -872,9 +873,10 @@ nouveau_gem_ioctl_pushbuf(struct drm_device *dev, void
*data,
>                                 break;
>                         }
>                 }
> -               u_free(reloc);
>         }
>  out_prevalid:
> +       if (!IS_ERR(reloc))
> +               u_free(reloc);
>         u_free(bo);
>         u_free(push);
>
>
> base-commit: 3494d58865ad4a47611dbb427b214cc5227fa5eb
> --
> 2.29.2
>

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch