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Message-ID: <59d4bf96-9a94-4e2c-9636-81e79d572438@redhat.com>
Date: Mon, 27 May 2024 13:23:53 +0200
From: Danilo Krummrich <dakr@...hat.com>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Karol Herbst <kherbst@...hat.com>, Lyude Paul <lyude@...hat.com>,
Daniel Vetter <daniel@...ll.ch>, dri-devel@...ts.freedesktop.org,
nouveau@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
Javier Martinez Canillas <javierm@...hat.com>,
Jani Nikula <jani.nikula@...el.com>, Thomas Zimmermann
<tzimmermann@...e.de>, Maxime Ripard <mripard@...nel.org>,
Kees Cook <keescook@...omium.org>,
Christophe JAILLET <christophe.jaillet@...adoo.fr>,
Joe Perches <joe@...ches.com>, David Airlie <airlied@...il.com>
Subject: Re: [PATCH v3] drm/nouveau/nvif: Avoid build error due to potential
integer overflows
On 5/24/24 15:48, Guenter Roeck wrote:
> Trying to build parisc:allmodconfig with gcc 12.x or later results
> in the following build error.
>
> drivers/gpu/drm/nouveau/nvif/object.c: In function 'nvif_object_mthd':
> drivers/gpu/drm/nouveau/nvif/object.c:161:9: error:
> 'memcpy' accessing 4294967264 or more bytes at offsets 0 and 32 overlaps 6442450881 bytes at offset -2147483617 [-Werror=restrict]
> 161 | memcpy(data, args->mthd.data, size);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/gpu/drm/nouveau/nvif/object.c: In function 'nvif_object_ctor':
> drivers/gpu/drm/nouveau/nvif/object.c:298:17: error:
> 'memcpy' accessing 4294967240 or more bytes at offsets 0 and 56 overlaps 6442450833 bytes at offset -2147483593 [-Werror=restrict]
> 298 | memcpy(data, args->new.data, size);
>
> gcc assumes that 'sizeof(*args) + size' can overflow, which would result
> in the problem.
>
> The problem is not new, only it is now no longer a warning but an error
> since W=1 has been enabled for the drm subsystem and since Werror is
> enabled for test builds.
>
> Rearrange arithmetic and use check_add_overflow() for validating the
> allocation size to avoid the overflow. While at it, split assignments
> out of if conditions.
>
> Fixes: a61ddb4393ad ("drm: enable (most) W=1 warnings by default across the subsystem")
> Cc: Javier Martinez Canillas <javierm@...hat.com>
> Cc: Jani Nikula <jani.nikula@...el.com>
> Cc: Thomas Zimmermann <tzimmermann@...e.de>
> Cc: Danilo Krummrich <dakr@...hat.com>
> Cc: Maxime Ripard <mripard@...nel.org>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> Cc: Joe Perches <joe@...ches.com>
> Reviewed-by: Kees Cook <keescook@...omium.org>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
Applied to drm-misc-fixes, thanks!
> ---
> v3: Split assignments from if conditions.
> v2: Use check_add_overflow() to calculate the allocation size and to check
> for overflows.
>
> drivers/gpu/drm/nouveau/nvif/object.c | 24 ++++++++++++++++++------
> 1 file changed, 18 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nvif/object.c b/drivers/gpu/drm/nouveau/nvif/object.c
> index 4d1aaee8fe15..1d19c87eaec1 100644
> --- a/drivers/gpu/drm/nouveau/nvif/object.c
> +++ b/drivers/gpu/drm/nouveau/nvif/object.c
> @@ -142,11 +142,16 @@ nvif_object_mthd(struct nvif_object *object, u32 mthd, void *data, u32 size)
> struct nvif_ioctl_v0 ioctl;
> struct nvif_ioctl_mthd_v0 mthd;
> } *args;
> + u32 args_size;
> u8 stack[128];
> int ret;
>
> - if (sizeof(*args) + size > sizeof(stack)) {
> - if (!(args = kmalloc(sizeof(*args) + size, GFP_KERNEL)))
> + if (check_add_overflow(sizeof(*args), size, &args_size))
> + return -ENOMEM;
> +
> + if (args_size > sizeof(stack)) {
> + args = kmalloc(args_size, GFP_KERNEL);
> + if (!args)
> return -ENOMEM;
> } else {
> args = (void *)stack;
> @@ -157,7 +162,7 @@ nvif_object_mthd(struct nvif_object *object, u32 mthd, void *data, u32 size)
> args->mthd.method = mthd;
>
> memcpy(args->mthd.data, data, size);
> - ret = nvif_object_ioctl(object, args, sizeof(*args) + size, NULL);
> + ret = nvif_object_ioctl(object, args, args_size, NULL);
> memcpy(data, args->mthd.data, size);
> if (args != (void *)stack)
> kfree(args);
> @@ -276,7 +281,15 @@ nvif_object_ctor(struct nvif_object *parent, const char *name, u32 handle,
> object->map.size = 0;
>
> if (parent) {
> - if (!(args = kmalloc(sizeof(*args) + size, GFP_KERNEL))) {
> + u32 args_size;
> +
> + if (check_add_overflow(sizeof(*args), size, &args_size)) {
> + nvif_object_dtor(object);
> + return -ENOMEM;
> + }
> +
> + args = kmalloc(args_size, GFP_KERNEL);
> + if (!args) {
> nvif_object_dtor(object);
> return -ENOMEM;
> }
> @@ -293,8 +306,7 @@ nvif_object_ctor(struct nvif_object *parent, const char *name, u32 handle,
> args->new.oclass = oclass;
>
> memcpy(args->new.data, data, size);
> - ret = nvif_object_ioctl(parent, args, sizeof(*args) + size,
> - &object->priv);
> + ret = nvif_object_ioctl(parent, args, args_size, &object->priv);
> memcpy(data, args->new.data, size);
> kfree(args);
> if (ret == 0)
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