[PATCH] drm/i915: Fix integer overflow tests

[PATCH] drm/i915: Fix integer overflow tests

[Dan Carpenter]

There are some potential integer overflows here on 64 bit systems.

The condition "if (nfences > SIZE_MAX / sizeof(*fences))" can only be
true on 32 bit systems, it's a no-op on 64 bit, so let's ignore the
check for now and look a couple lines after:

	if (!access_ok(VERIFY_READ, user, nfences * 2 * sizeof(u32)))
                                          ^^^^^^^^^^^
"nfences" is an unsigned int, so if we set it to UINT_MAX and multiply
by two, it's going to have an integer overflow.  The "args->buffer_count"
is also an unsigned int so it could overflow if it's set to UINT_MAX
when we do:

	exec2_list = kvmalloc_array(args->buffer_count + 1, sz,
                                    ^^^^^^^^^^^^^^^^^^^^^^
Fixes: 2889caa92321 ("drm/i915: Eliminate lots of iterations over the execobjects array")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 15ab3e6792f9..f569721aad1a 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -2152,7 +2152,7 @@ get_fence_array(struct drm_i915_gem_execbuffer2 *args,
 	if (!(args->flags & I915_EXEC_FENCE_ARRAY))
 		return NULL;
 
-	if (nfences > SIZE_MAX / sizeof(*fences))
+	if (nfences > UINT_MAX / sizeof(*fences))
 		return ERR_PTR(-EINVAL);
 
 	user = u64_to_user_ptr(args->cliprects_ptr);
@@ -2520,7 +2520,7 @@ i915_gem_execbuffer(struct drm_device *dev, void *data,
 	unsigned int i;
 	int err;
 
-	if (args->buffer_count < 1 || args->buffer_count > SIZE_MAX / sz - 1) {
+	if (args->buffer_count < 1 || args->buffer_count > UINT_MAX / sz - 1) {
 		DRM_DEBUG("execbuf2 with %d buffers\n", args->buffer_count);
 		return -EINVAL;
 	}
@@ -2609,7 +2609,7 @@ i915_gem_execbuffer2(struct drm_device *dev, void *data,
 	struct drm_syncobj **fences = NULL;
 	int err;
 
-	if (args->buffer_count < 1 || args->buffer_count > SIZE_MAX / sz - 1) {
+	if (args->buffer_count < 1 || args->buffer_count > UINT_MAX / sz - 1) {
 		DRM_DEBUG("execbuf2 with %d buffers\n", args->buffer_count);
 		return -EINVAL;
 	}
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Re: [PATCH] drm/i915: Fix integer overflow tests

[Imre Deak]

On Thu, Aug 17, 2017 at 09:23:10AM +0300, Dan Carpenter wrote:
> There are some potential integer overflows here on 64 bit systems.
> 
> The condition "if (nfences > SIZE_MAX / sizeof(*fences))" can only be
> true on 32 bit systems, it's a no-op on 64 bit, so let's ignore the
> check for now and look a couple lines after:
> 
> 	if (!access_ok(VERIFY_READ, user, nfences * 2 * sizeof(u32)))
>                                           ^^^^^^^^^^^
> "nfences" is an unsigned int, so if we set it to UINT_MAX and multiply
> by two, it's going to have an integer overflow.  

AFAICS it wouldn't overflow due the promotion to unsigned long
by '* sizeof(u32)'.

> The "args->buffer_count"
> is also an unsigned int so it could overflow if it's set to UINT_MAX
> when we do:
> 
> 	exec2_list = kvmalloc_array(args->buffer_count + 1, sz,
>                                     ^^^^^^^^^^^^^^^^^^^^^^

Yes, this could overflow.

> Fixes: 2889caa92321 ("drm/i915: Eliminate lots of iterations over the execobjects array")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> index 15ab3e6792f9..f569721aad1a 100644
> --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> @@ -2152,7 +2152,7 @@ get_fence_array(struct drm_i915_gem_execbuffer2 *args,
>  	if (!(args->flags & I915_EXEC_FENCE_ARRAY))
>  		return NULL;
>  
> -	if (nfences > SIZE_MAX / sizeof(*fences))
> +	if (nfences > UINT_MAX / sizeof(*fences))
>  		return ERR_PTR(-EINVAL);
>  
>  	user = u64_to_user_ptr(args->cliprects_ptr);
> @@ -2520,7 +2520,7 @@ i915_gem_execbuffer(struct drm_device *dev, void *data,
>  	unsigned int i;
>  	int err;
>  
> -	if (args->buffer_count < 1 || args->buffer_count > SIZE_MAX / sz - 1) {
> +	if (args->buffer_count < 1 || args->buffer_count > UINT_MAX / sz - 1) {
>  		DRM_DEBUG("execbuf2 with %d buffers\n", args->buffer_count);
>  		return -EINVAL;
>  	}
> @@ -2609,7 +2609,7 @@ i915_gem_execbuffer2(struct drm_device *dev, void *data,
>  	struct drm_syncobj **fences = NULL;
>  	int err;
>  
> -	if (args->buffer_count < 1 || args->buffer_count > SIZE_MAX / sz - 1) {
> +	if (args->buffer_count < 1 || args->buffer_count > UINT_MAX / sz - 1) {
>  		DRM_DEBUG("execbuf2 with %d buffers\n", args->buffer_count);
>  		return -EINVAL;
>  	}
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [PATCH] drm/i915: Fix integer overflow tests

[Dan Carpenter]

On Thu, Aug 17, 2017 at 12:37:00PM +0300, Imre Deak wrote:
> On Thu, Aug 17, 2017 at 09:23:10AM +0300, Dan Carpenter wrote:
> > There are some potential integer overflows here on 64 bit systems.
> > 
> > The condition "if (nfences > SIZE_MAX / sizeof(*fences))" can only be
> > true on 32 bit systems, it's a no-op on 64 bit, so let's ignore the
> > check for now and look a couple lines after:
> > 
> > 	if (!access_ok(VERIFY_READ, user, nfences * 2 * sizeof(u32)))
> >                                           ^^^^^^^^^^^
> > "nfences" is an unsigned int, so if we set it to UINT_MAX and multiply
> > by two, it's going to have an integer overflow.  
> 
> AFAICS it wouldn't overflow due the promotion to unsigned long
> by '* sizeof(u32)'.
> 

It first multplies "nfences * 2" as unsigned int, then it type promotes
to size_t and multiplies by sizeof().  Only the first multiplication has
an integer overflow bug.

regards,
dan carpenter

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Re: [PATCH] drm/i915: Fix integer overflow tests

[Imre Deak]

On Thu, Aug 17, 2017 at 12:50:37PM +0300, Dan Carpenter wrote:
> On Thu, Aug 17, 2017 at 12:37:00PM +0300, Imre Deak wrote:
> > On Thu, Aug 17, 2017 at 09:23:10AM +0300, Dan Carpenter wrote:
> > > There are some potential integer overflows here on 64 bit systems.
> > > 
> > > The condition "if (nfences > SIZE_MAX / sizeof(*fences))" can only be
> > > true on 32 bit systems, it's a no-op on 64 bit, so let's ignore the
> > > check for now and look a couple lines after:
> > > 
> > > 	if (!access_ok(VERIFY_READ, user, nfences * 2 * sizeof(u32)))
> > >                                           ^^^^^^^^^^^
> > > "nfences" is an unsigned int, so if we set it to UINT_MAX and multiply
> > > by two, it's going to have an integer overflow.  
> > 
> > AFAICS it wouldn't overflow due the promotion to unsigned long
> > by '* sizeof(u32)'.
> > 
> 
> It first multplies "nfences * 2" as unsigned int, then it type promotes
> to size_t and multiplies by sizeof().  Only the first multiplication has
> an integer overflow bug.

Err, that's correct. Sorry for the noise.

> 
> regards,
> dan carpenter
> 
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Re: [PATCH] drm/i915: Fix integer overflow tests

[Jason Ekstrand]

[-- Attachment #1.1: Type: text/plain, Size: 1351 bytes --]

On Thu, Aug 17, 2017 at 2:56 AM, Imre Deak <imre.deak@intel.com> wrote:

> On Thu, Aug 17, 2017 at 12:50:37PM +0300, Dan Carpenter wrote:
> > On Thu, Aug 17, 2017 at 12:37:00PM +0300, Imre Deak wrote:
> > > On Thu, Aug 17, 2017 at 09:23:10AM +0300, Dan Carpenter wrote:
> > > > There are some potential integer overflows here on 64 bit systems.
> > > >
> > > > The condition "if (nfences > SIZE_MAX / sizeof(*fences))" can only be
> > > > true on 32 bit systems, it's a no-op on 64 bit, so let's ignore the
> > > > check for now and look a couple lines after:
> > > >
> > > >   if (!access_ok(VERIFY_READ, user, nfences * 2 * sizeof(u32)))
> > > >                                           ^^^^^^^^^^^
> > > > "nfences" is an unsigned int, so if we set it to UINT_MAX and
> multiply
> > > > by two, it's going to have an integer overflow.
> > >
> > > AFAICS it wouldn't overflow due the promotion to unsigned long
> > > by '* sizeof(u32)'.
> > >
> >
> > It first multplies "nfences * 2" as unsigned int, then it type promotes
> > to size_t and multiplies by sizeof().  Only the first multiplication has
> > an integer overflow bug.
>
> Err, that's correct. Sorry for the noise.
>

Why not just replace the "2 * sizeof(u32)" with a "sizeof(*user)".  That's
what we really want to check.  I have no idea how it ended up being "2 *
sizeof(u32)"

--Jason

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Re: [PATCH] drm/i915: Fix integer overflow tests

[Dan Carpenter]

On Thu, Aug 17, 2017 at 07:16:03AM -0700, Jason Ekstrand wrote:
> On Thu, Aug 17, 2017 at 2:56 AM, Imre Deak <imre.deak@intel.com> wrote:
> 
> > On Thu, Aug 17, 2017 at 12:50:37PM +0300, Dan Carpenter wrote:
> > > On Thu, Aug 17, 2017 at 12:37:00PM +0300, Imre Deak wrote:
> > > > On Thu, Aug 17, 2017 at 09:23:10AM +0300, Dan Carpenter wrote:
> > > > > There are some potential integer overflows here on 64 bit systems.
> > > > >
> > > > > The condition "if (nfences > SIZE_MAX / sizeof(*fences))" can only be
> > > > > true on 32 bit systems, it's a no-op on 64 bit, so let's ignore the
> > > > > check for now and look a couple lines after:
> > > > >
> > > > >   if (!access_ok(VERIFY_READ, user, nfences * 2 * sizeof(u32)))
> > > > >                                           ^^^^^^^^^^^
> > > > > "nfences" is an unsigned int, so if we set it to UINT_MAX and
> > multiply
> > > > > by two, it's going to have an integer overflow.
> > > >
> > > > AFAICS it wouldn't overflow due the promotion to unsigned long
> > > > by '* sizeof(u32)'.
> > > >
> > >
> > > It first multplies "nfences * 2" as unsigned int, then it type promotes
> > > to size_t and multiplies by sizeof().  Only the first multiplication has
> > > an integer overflow bug.
> >
> > Err, that's correct. Sorry for the noise.
> >
> 
> Why not just replace the "2 * sizeof(u32)" with a "sizeof(*user)".  That's
> what we really want to check.  I have no idea how it ended up being "2 *
> sizeof(u32)"

Yeah.  That's more readable.  I will resend.

regards,
dan carpenter


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[PATCH v2] drm/i915: Fix integer overflow tests

[Dan Carpenter]

There are some potential integer overflows here on 64 bit systems.

The condition "if (nfences > SIZE_MAX / sizeof(*fences))" can only be
true on 32 bit systems, it's a no-op on 64 bit, so let's ignore the
check for now and look a couple lines after:

        if (!access_ok(VERIFY_READ, user, nfences * 2 * sizeof(u32)))
                                          ^^^^^^^^^^^
"nfences" is an unsigned int, so if we set it to UINT_MAX and multiply
by two, it's going to have an integer overflow.  The multiplication by
sizeof(u32) is OK because that gets type promoted to size_t.  This patch
changes the access_ok() check to use sizeof(*user) which fixes the
integer overflow and is also more readable.

The "args->buffer_count" variable is an unsigned int as well so it could
overflow if it's set to UINT_MAX when we do:

        exec2_list = kvmalloc_array(args->buffer_count + 1, sz,
                                    ^^^^^^^^^^^^^^^^^^^^^^

Originally, those two integer overflow checks were against UINT_MAX
instead of SIZE_MAX and this patch changes them back.

Fixes: 2889caa92321 ("drm/i915: Eliminate lots of iterations over the execobjects array")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
v2: Use sizeof(*users)

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 15ab3e6792f9..11419b81cf13 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -2156,7 +2156,7 @@ get_fence_array(struct drm_i915_gem_execbuffer2 *args,
 		return ERR_PTR(-EINVAL);
 
 	user = u64_to_user_ptr(args->cliprects_ptr);
-	if (!access_ok(VERIFY_READ, user, nfences * 2 * sizeof(u32)))
+	if (!access_ok(VERIFY_READ, user, nfences * sizeof(*user)))
 		return ERR_PTR(-EFAULT);
 
 	fences = kvmalloc_array(args->num_cliprects, sizeof(*fences),
@@ -2520,7 +2520,7 @@ i915_gem_execbuffer(struct drm_device *dev, void *data,
 	unsigned int i;
 	int err;
 
-	if (args->buffer_count < 1 || args->buffer_count > SIZE_MAX / sz - 1) {
+	if (args->buffer_count < 1 || args->buffer_count > UINT_MAX / sz - 1) {
 		DRM_DEBUG("execbuf2 with %d buffers\n", args->buffer_count);
 		return -EINVAL;
 	}
@@ -2609,7 +2609,7 @@ i915_gem_execbuffer2(struct drm_device *dev, void *data,
 	struct drm_syncobj **fences = NULL;
 	int err;
 
-	if (args->buffer_count < 1 || args->buffer_count > SIZE_MAX / sz - 1) {
+	if (args->buffer_count < 1 || args->buffer_count > UINT_MAX / sz - 1) {
 		DRM_DEBUG("execbuf2 with %d buffers\n", args->buffer_count);
 		return -EINVAL;
 	}
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Re: [PATCH v2] drm/i915: Fix integer overflow tests

[Chris Wilson]

Quoting Dan Carpenter (2017-08-18 08:07:00)
> There are some potential integer overflows here on 64 bit systems.
> 
> The condition "if (nfences > SIZE_MAX / sizeof(*fences))" can only be
> true on 32 bit systems, it's a no-op on 64 bit, so let's ignore the
> check for now and look a couple lines after:
> 
>         if (!access_ok(VERIFY_READ, user, nfences * 2 * sizeof(u32)))
>                                           ^^^^^^^^^^^
> "nfences" is an unsigned int, so if we set it to UINT_MAX and multiply
> by two, it's going to have an integer overflow.  The multiplication by
> sizeof(u32) is OK because that gets type promoted to size_t.  This patch
> changes the access_ok() check to use sizeof(*user) which fixes the
> integer overflow and is also more readable.
> 
> The "args->buffer_count" variable is an unsigned int as well so it could
> overflow if it's set to UINT_MAX when we do:
> 
>         exec2_list = kvmalloc_array(args->buffer_count + 1, sz,
>                                     ^^^^^^^^^^^^^^^^^^^^^^
> 
> Originally, those two integer overflow checks were against UINT_MAX
> instead of SIZE_MAX and this patch changes them back.
> 
> Fixes: 2889caa92321 ("drm/i915: Eliminate lots of iterations over the execobjects array")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> v2: Use sizeof(*users)

Please do consider my alternative.
-Chris

Re: [PATCH v2] drm/i915: Fix integer overflow tests

[Dan Carpenter]

On Fri, Aug 18, 2017 at 08:46:25AM +0100, Chris Wilson wrote:
> Quoting Dan Carpenter (2017-08-18 08:07:00)
> > There are some potential integer overflows here on 64 bit systems.
> > 
> > The condition "if (nfences > SIZE_MAX / sizeof(*fences))" can only be
> > true on 32 bit systems, it's a no-op on 64 bit, so let's ignore the
> > check for now and look a couple lines after:
> > 
> >         if (!access_ok(VERIFY_READ, user, nfences * 2 * sizeof(u32)))
> >                                           ^^^^^^^^^^^
> > "nfences" is an unsigned int, so if we set it to UINT_MAX and multiply
> > by two, it's going to have an integer overflow.  The multiplication by
> > sizeof(u32) is OK because that gets type promoted to size_t.  This patch
> > changes the access_ok() check to use sizeof(*user) which fixes the
> > integer overflow and is also more readable.
> > 
> > The "args->buffer_count" variable is an unsigned int as well so it could
> > overflow if it's set to UINT_MAX when we do:
> > 
> >         exec2_list = kvmalloc_array(args->buffer_count + 1, sz,
> >                                     ^^^^^^^^^^^^^^^^^^^^^^
> > 
> > Originally, those two integer overflow checks were against UINT_MAX
> > instead of SIZE_MAX and this patch changes them back.
> > 
> > Fixes: 2889caa92321 ("drm/i915: Eliminate lots of iterations over the execobjects array")
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > ---
> > v2: Use sizeof(*users)
> 
> Please do consider my alternative.

I don't think you sent the email?  I haven't recieved any emails from
you on either my oracle.com address or through the kernel janitors list.

Can you resend?

regards
dan carpenter