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From:   Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Mon, 23 Nov 2020 10:51:25 +0100
Message-ID: <CAKMK7uGDY+aLP-yYwyW5t-usUK3XM-oU9ZLHm1_jU0BTjJUN+g@mail.gmail.com>
Subject: Re: [PATCH] drm/nouveau: fix relocations applying logic and a double-free
To:     Matti Hamalainen <ccr@tnsp.org>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Ben Skeggs <bskeggs@redhat.com>,
        Nouveau Dev <nouveau@lists.freedesktop.org>,
        dri-devel <dri-devel@lists.freedesktop.org>
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On Fri, Nov 20, 2020 at 4:23 PM Matti Hamalainen <ccr@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@ffwll.ch>
> Cc: Ben Skeggs <bskeggs@redhat.com>
> Cc: nouveau@lists.freedesktop.org
> Cc: dri-devel@lists.freedesktop.org
> Signed-off-by: Matti Hamalainen <ccr@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@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