[PATCH] media: omap3isp: Extract struct group for memcpy() region

[PATCH] media: omap3isp: Extract struct group for memcpy() region

[Kees Cook]

Avoid writing past the end of a structure member by wrapping the target
region in a common named structure. This additionally fixes a
misalignment of the copy (since the size of "buf" changes between 64-bit
and 32-bit).

I actually think this code is completely unused in the real world:
I don't think it could have ever worked, as it would either always
fail (with an uninitialized data->buf_size) or would cause corruption
in userspace due to the copy_to_user() in the call path against an
uninitialized data->buf value:

omap3isp_stat_request_statistics_time32(...)
    struct omap3isp_stat_data data64;
    ...
    omap3isp_stat_request_statistics(stat, &data64);

int omap3isp_stat_request_statistics(struct ispstat *stat,
                                     struct omap3isp_stat_data *data)
    ...
    buf = isp_stat_buf_get(stat, data);

static struct ispstat_buffer *isp_stat_buf_get(struct ispstat *stat,
                                               struct omap3isp_stat_data *data)
...
    if (buf->buf_size > data->buf_size) {
            ...
            return ERR_PTR(-EINVAL);
    }
    ...
    rval = copy_to_user(data->buf,
                        buf->virt_addr,
                        buf->buf_size);

Regardless, additionally initialize data64 to be zero-filled to avoid
undefined behavior.

Fixes: 378e3f81cb56 ("media: omap3isp: support 64-bit version of omap3isp_stat_data")
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/media/platform/omap3isp/ispstat.c |  5 +--
 include/uapi/linux/omap3isp.h             | 44 +++++++++++++++++------
 2 files changed, 36 insertions(+), 13 deletions(-)

diff --git a/drivers/media/platform/omap3isp/ispstat.c b/drivers/media/platform/omap3isp/ispstat.c
index 5b9b57f4d9bf..ea8222fed38e 100644
--- a/drivers/media/platform/omap3isp/ispstat.c
+++ b/drivers/media/platform/omap3isp/ispstat.c
@@ -512,7 +512,7 @@ int omap3isp_stat_request_statistics(struct ispstat *stat,
 int omap3isp_stat_request_statistics_time32(struct ispstat *stat,
 					struct omap3isp_stat_data_time32 *data)
 {
-	struct omap3isp_stat_data data64;
+	struct omap3isp_stat_data data64 = { };
 	int ret;
 
 	ret = omap3isp_stat_request_statistics(stat, &data64);
@@ -521,7 +521,8 @@ int omap3isp_stat_request_statistics_time32(struct ispstat *stat,
 
 	data->ts.tv_sec = data64.ts.tv_sec;
 	data->ts.tv_usec = data64.ts.tv_usec;
-	memcpy(&data->buf, &data64.buf, sizeof(*data) - sizeof(data->ts));
+	data->buf = (uintptr_t)data64.buf;
+	memcpy(&data->frame, &data64.buf, sizeof(data->frame));
 
 	return 0;
 }
diff --git a/include/uapi/linux/omap3isp.h b/include/uapi/linux/omap3isp.h
index 87b55755f4ff..0a16af91621f 100644
--- a/include/uapi/linux/omap3isp.h
+++ b/include/uapi/linux/omap3isp.h
@@ -159,13 +159,25 @@ struct omap3isp_h3a_aewb_config {
 };
 
 /**
- * struct omap3isp_stat_data - Statistic data sent to or received from user
- * @ts: Timestamp of returned framestats.
- * @buf: Pointer to pass to user.
+ * struct omap3isp_stat_frame - Statistic data without timestamp nor pointer.
+ * @buf_size: Size of buffer.
  * @frame_number: Frame number of requested stats.
  * @cur_frame: Current frame number being processed.
  * @config_counter: Number of the configuration associated with the data.
  */
+struct omap3isp_stat_frame {
+	__u32 buf_size;
+	__u16 frame_number;
+	__u16 cur_frame;
+	__u16 config_counter;
+};
+
+/**
+ * struct omap3isp_stat_data - Statistic data sent to or received from user
+ * @ts: Timestamp of returned framestats.
+ * @buf: Pointer to pass to user.
+ * @frame: Statistic data for frame.
+ */
 struct omap3isp_stat_data {
 #ifdef __KERNEL__
 	struct {
@@ -176,10 +188,15 @@ struct omap3isp_stat_data {
 	struct timeval ts;
 #endif
 	void __user *buf;
-	__u32 buf_size;
-	__u16 frame_number;
-	__u16 cur_frame;
-	__u16 config_counter;
+	union {
+		struct {
+			__u32 buf_size;
+			__u16 frame_number;
+			__u16 cur_frame;
+			__u16 config_counter;
+		};
+		struct omap3isp_stat_frame frame;
+	};
 };
 
 #ifdef __KERNEL__
@@ -189,10 +206,15 @@ struct omap3isp_stat_data_time32 {
 		__s32	tv_usec;
 	} ts;
 	__u32 buf;
-	__u32 buf_size;
-	__u16 frame_number;
-	__u16 cur_frame;
-	__u16 config_counter;
+	union {
+		struct {
+			__u32 buf_size;
+			__u16 frame_number;
+			__u16 cur_frame;
+			__u16 config_counter;
+		};
+		struct omap3isp_stat_frame frame;
+	};
 };
 #endif
 
-- 
2.25.1

Re: [PATCH] media: omap3isp: Extract struct group for memcpy() region

[Laurent Pinchart]

Hi Kees,

Thank you for the patch.

On Wed, Jun 16, 2021 at 11:59:38AM -0700, Kees Cook wrote:
> Avoid writing past the end of a structure member by wrapping the target
> region in a common named structure. This additionally fixes a
> misalignment of the copy (since the size of "buf" changes between 64-bit
> and 32-bit).

Could you have been mislead by the data64 name ? The difference between
omap3isp_stat_data_time and omap3isp_stat_data_time32 is the size of the
ts field, using 32-bit timestamps with legacy userspace, and 64-bit
timestamps with more recent userspace. In both cases we're dealing with
a 32-bit platform, as the omap3isp is not used in any 64-bit ARM SoC.
The size of void __user *buf is thus 4 bytes in all cases, as is __u32
buf.

> I actually think this code is completely unused in the real world:
> I don't think it could have ever worked, as it would either always
> fail (with an uninitialized data->buf_size) or would cause corruption
> in userspace due to the copy_to_user() in the call path against an
> uninitialized data->buf value:
> 
> omap3isp_stat_request_statistics_time32(...)
>     struct omap3isp_stat_data data64;
>     ...
>     omap3isp_stat_request_statistics(stat, &data64);
> 
> int omap3isp_stat_request_statistics(struct ispstat *stat,
>                                      struct omap3isp_stat_data *data)
>     ...
>     buf = isp_stat_buf_get(stat, data);
> 
> static struct ispstat_buffer *isp_stat_buf_get(struct ispstat *stat,
>                                                struct omap3isp_stat_data *data)
> ...
>     if (buf->buf_size > data->buf_size) {
>             ...
>             return ERR_PTR(-EINVAL);
>     }
>     ...
>     rval = copy_to_user(data->buf,
>                         buf->virt_addr,
>                         buf->buf_size);
> 
> Regardless, additionally initialize data64 to be zero-filled to avoid
> undefined behavior.
> 
> Fixes: 378e3f81cb56 ("media: omap3isp: support 64-bit version of omap3isp_stat_data")
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  drivers/media/platform/omap3isp/ispstat.c |  5 +--
>  include/uapi/linux/omap3isp.h             | 44 +++++++++++++++++------
>  2 files changed, 36 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/media/platform/omap3isp/ispstat.c b/drivers/media/platform/omap3isp/ispstat.c
> index 5b9b57f4d9bf..ea8222fed38e 100644
> --- a/drivers/media/platform/omap3isp/ispstat.c
> +++ b/drivers/media/platform/omap3isp/ispstat.c
> @@ -512,7 +512,7 @@ int omap3isp_stat_request_statistics(struct ispstat *stat,
>  int omap3isp_stat_request_statistics_time32(struct ispstat *stat,
>  					struct omap3isp_stat_data_time32 *data)
>  {
> -	struct omap3isp_stat_data data64;
> +	struct omap3isp_stat_data data64 = { };
>  	int ret;
>  
>  	ret = omap3isp_stat_request_statistics(stat, &data64);
> @@ -521,7 +521,8 @@ int omap3isp_stat_request_statistics_time32(struct ispstat *stat,
>  
>  	data->ts.tv_sec = data64.ts.tv_sec;
>  	data->ts.tv_usec = data64.ts.tv_usec;
> -	memcpy(&data->buf, &data64.buf, sizeof(*data) - sizeof(data->ts));
> +	data->buf = (uintptr_t)data64.buf;
> +	memcpy(&data->frame, &data64.buf, sizeof(data->frame));
>  
>  	return 0;
>  }
> diff --git a/include/uapi/linux/omap3isp.h b/include/uapi/linux/omap3isp.h
> index 87b55755f4ff..0a16af91621f 100644
> --- a/include/uapi/linux/omap3isp.h
> +++ b/include/uapi/linux/omap3isp.h
> @@ -159,13 +159,25 @@ struct omap3isp_h3a_aewb_config {
>  };
>  
>  /**
> - * struct omap3isp_stat_data - Statistic data sent to or received from user
> - * @ts: Timestamp of returned framestats.
> - * @buf: Pointer to pass to user.
> + * struct omap3isp_stat_frame - Statistic data without timestamp nor pointer.
> + * @buf_size: Size of buffer.
>   * @frame_number: Frame number of requested stats.
>   * @cur_frame: Current frame number being processed.
>   * @config_counter: Number of the configuration associated with the data.
>   */
> +struct omap3isp_stat_frame {
> +	__u32 buf_size;
> +	__u16 frame_number;
> +	__u16 cur_frame;
> +	__u16 config_counter;
> +};
> +
> +/**
> + * struct omap3isp_stat_data - Statistic data sent to or received from user
> + * @ts: Timestamp of returned framestats.
> + * @buf: Pointer to pass to user.
> + * @frame: Statistic data for frame.
> + */
>  struct omap3isp_stat_data {
>  #ifdef __KERNEL__
>  	struct {
> @@ -176,10 +188,15 @@ struct omap3isp_stat_data {
>  	struct timeval ts;
>  #endif
>  	void __user *buf;
> -	__u32 buf_size;
> -	__u16 frame_number;
> -	__u16 cur_frame;
> -	__u16 config_counter;
> +	union {
> +		struct {
> +			__u32 buf_size;
> +			__u16 frame_number;
> +			__u16 cur_frame;
> +			__u16 config_counter;
> +		};
> +		struct omap3isp_stat_frame frame;
> +	};
>  };
>  
>  #ifdef __KERNEL__
> @@ -189,10 +206,15 @@ struct omap3isp_stat_data_time32 {
>  		__s32	tv_usec;
>  	} ts;
>  	__u32 buf;
> -	__u32 buf_size;
> -	__u16 frame_number;
> -	__u16 cur_frame;
> -	__u16 config_counter;
> +	union {
> +		struct {
> +			__u32 buf_size;
> +			__u16 frame_number;
> +			__u16 cur_frame;
> +			__u16 config_counter;
> +		};
> +		struct omap3isp_stat_frame frame;
> +	};
>  };
>  #endif
>  

-- 
Regards,

Laurent Pinchart

Re: [PATCH] media: omap3isp: Extract struct group for memcpy() region

[Kees Cook]

On Wed, Jun 16, 2021 at 10:43:03PM +0300, Laurent Pinchart wrote:
> Hi Kees,
> 
> Thank you for the patch.
> 
> On Wed, Jun 16, 2021 at 11:59:38AM -0700, Kees Cook wrote:
> > Avoid writing past the end of a structure member by wrapping the target
> > region in a common named structure. This additionally fixes a
> > misalignment of the copy (since the size of "buf" changes between 64-bit
> > and 32-bit).
> 
> Could you have been mislead by the data64 name ? The difference between
> omap3isp_stat_data_time and omap3isp_stat_data_time32 is the size of the
> ts field, using 32-bit timestamps with legacy userspace, and 64-bit
> timestamps with more recent userspace. In both cases we're dealing with
> a 32-bit platform, as the omap3isp is not used in any 64-bit ARM SoC.
> The size of void __user *buf is thus 4 bytes in all cases, as is __u32
> buf.

Ah, yes, that's true. I was hitting this on arm64 builds
(CONFIG_COMPILE_TEST) where __user *buf is 64-bit. So, the "additionally
fixes" bit above is misleading in the sense that nothing was ever built
in the real world like that.

The patch still fixes the compile-time warnings, though.

However, I don't think anything actually uses any of this code
regardless. ;)

-Kees

> 
> > I actually think this code is completely unused in the real world:
> > I don't think it could have ever worked, as it would either always
> > fail (with an uninitialized data->buf_size) or would cause corruption
> > in userspace due to the copy_to_user() in the call path against an
> > uninitialized data->buf value:
> > 
> > omap3isp_stat_request_statistics_time32(...)
> >     struct omap3isp_stat_data data64;
> >     ...
> >     omap3isp_stat_request_statistics(stat, &data64);
> > 
> > int omap3isp_stat_request_statistics(struct ispstat *stat,
> >                                      struct omap3isp_stat_data *data)
> >     ...
> >     buf = isp_stat_buf_get(stat, data);
> > 
> > static struct ispstat_buffer *isp_stat_buf_get(struct ispstat *stat,
> >                                                struct omap3isp_stat_data *data)
> > ...
> >     if (buf->buf_size > data->buf_size) {
> >             ...
> >             return ERR_PTR(-EINVAL);
> >     }
> >     ...
> >     rval = copy_to_user(data->buf,
> >                         buf->virt_addr,
> >                         buf->buf_size);
> > 
> > Regardless, additionally initialize data64 to be zero-filled to avoid
> > undefined behavior.
> > 
> > Fixes: 378e3f81cb56 ("media: omap3isp: support 64-bit version of omap3isp_stat_data")
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> >  drivers/media/platform/omap3isp/ispstat.c |  5 +--
> >  include/uapi/linux/omap3isp.h             | 44 +++++++++++++++++------
> >  2 files changed, 36 insertions(+), 13 deletions(-)
> > 
> > diff --git a/drivers/media/platform/omap3isp/ispstat.c b/drivers/media/platform/omap3isp/ispstat.c
> > index 5b9b57f4d9bf..ea8222fed38e 100644
> > --- a/drivers/media/platform/omap3isp/ispstat.c
> > +++ b/drivers/media/platform/omap3isp/ispstat.c
> > @@ -512,7 +512,7 @@ int omap3isp_stat_request_statistics(struct ispstat *stat,
> >  int omap3isp_stat_request_statistics_time32(struct ispstat *stat,
> >  					struct omap3isp_stat_data_time32 *data)
> >  {
> > -	struct omap3isp_stat_data data64;
> > +	struct omap3isp_stat_data data64 = { };
> >  	int ret;
> >  
> >  	ret = omap3isp_stat_request_statistics(stat, &data64);
> > @@ -521,7 +521,8 @@ int omap3isp_stat_request_statistics_time32(struct ispstat *stat,
> >  
> >  	data->ts.tv_sec = data64.ts.tv_sec;
> >  	data->ts.tv_usec = data64.ts.tv_usec;
> > -	memcpy(&data->buf, &data64.buf, sizeof(*data) - sizeof(data->ts));
> > +	data->buf = (uintptr_t)data64.buf;
> > +	memcpy(&data->frame, &data64.buf, sizeof(data->frame));
> >  
> >  	return 0;
> >  }
> > diff --git a/include/uapi/linux/omap3isp.h b/include/uapi/linux/omap3isp.h
> > index 87b55755f4ff..0a16af91621f 100644
> > --- a/include/uapi/linux/omap3isp.h
> > +++ b/include/uapi/linux/omap3isp.h
> > @@ -159,13 +159,25 @@ struct omap3isp_h3a_aewb_config {
> >  };
> >  
> >  /**
> > - * struct omap3isp_stat_data - Statistic data sent to or received from user
> > - * @ts: Timestamp of returned framestats.
> > - * @buf: Pointer to pass to user.
> > + * struct omap3isp_stat_frame - Statistic data without timestamp nor pointer.
> > + * @buf_size: Size of buffer.
> >   * @frame_number: Frame number of requested stats.
> >   * @cur_frame: Current frame number being processed.
> >   * @config_counter: Number of the configuration associated with the data.
> >   */
> > +struct omap3isp_stat_frame {
> > +	__u32 buf_size;
> > +	__u16 frame_number;
> > +	__u16 cur_frame;
> > +	__u16 config_counter;
> > +};
> > +
> > +/**
> > + * struct omap3isp_stat_data - Statistic data sent to or received from user
> > + * @ts: Timestamp of returned framestats.
> > + * @buf: Pointer to pass to user.
> > + * @frame: Statistic data for frame.
> > + */
> >  struct omap3isp_stat_data {
> >  #ifdef __KERNEL__
> >  	struct {
> > @@ -176,10 +188,15 @@ struct omap3isp_stat_data {
> >  	struct timeval ts;
> >  #endif
> >  	void __user *buf;
> > -	__u32 buf_size;
> > -	__u16 frame_number;
> > -	__u16 cur_frame;
> > -	__u16 config_counter;
> > +	union {
> > +		struct {
> > +			__u32 buf_size;
> > +			__u16 frame_number;
> > +			__u16 cur_frame;
> > +			__u16 config_counter;
> > +		};
> > +		struct omap3isp_stat_frame frame;
> > +	};
> >  };
> >  
> >  #ifdef __KERNEL__
> > @@ -189,10 +206,15 @@ struct omap3isp_stat_data_time32 {
> >  		__s32	tv_usec;
> >  	} ts;
> >  	__u32 buf;
> > -	__u32 buf_size;
> > -	__u16 frame_number;
> > -	__u16 cur_frame;
> > -	__u16 config_counter;
> > +	union {
> > +		struct {
> > +			__u32 buf_size;
> > +			__u16 frame_number;
> > +			__u16 cur_frame;
> > +			__u16 config_counter;
> > +		};
> > +		struct omap3isp_stat_frame frame;
> > +	};
> >  };
> >  #endif
> >  
> 
> -- 
> Regards,
> 
> Laurent Pinchart

-- 
Kees Cook

Re: [PATCH] media: omap3isp: Extract struct group for memcpy() region

[Laurent Pinchart]

Hi Kees,

On Wed, Jun 16, 2021 at 09:22:23PM -0700, Kees Cook wrote:
> On Wed, Jun 16, 2021 at 10:43:03PM +0300, Laurent Pinchart wrote:
> > On Wed, Jun 16, 2021 at 11:59:38AM -0700, Kees Cook wrote:
> > > Avoid writing past the end of a structure member by wrapping the target
> > > region in a common named structure. This additionally fixes a
> > > misalignment of the copy (since the size of "buf" changes between 64-bit
> > > and 32-bit).
> > 
> > Could you have been mislead by the data64 name ? The difference between
> > omap3isp_stat_data_time and omap3isp_stat_data_time32 is the size of the
> > ts field, using 32-bit timestamps with legacy userspace, and 64-bit
> > timestamps with more recent userspace. In both cases we're dealing with
> > a 32-bit platform, as the omap3isp is not used in any 64-bit ARM SoC.
> > The size of void __user *buf is thus 4 bytes in all cases, as is __u32
> > buf.
> 
> Ah, yes, that's true. I was hitting this on arm64 builds
> (CONFIG_COMPILE_TEST) where __user *buf is 64-bit. So, the "additionally
> fixes" bit above is misleading in the sense that nothing was ever built
> in the real world like that.
> 
> The patch still fixes the compile-time warnings, though.

I What's the compile-time warning ? I tried compiling the driver for
ARM64 and didn't notice any.

> However, I don't think anything actually uses any of this code
> regardless. ;)
> 
> > > I actually think this code is completely unused in the real world:
> > > I don't think it could have ever worked, as it would either always
> > > fail (with an uninitialized data->buf_size) or would cause corruption
> > > in userspace due to the copy_to_user() in the call path against an
> > > uninitialized data->buf value:
> > > 
> > > omap3isp_stat_request_statistics_time32(...)
> > >     struct omap3isp_stat_data data64;
> > >     ...
> > >     omap3isp_stat_request_statistics(stat, &data64);
> > > 
> > > int omap3isp_stat_request_statistics(struct ispstat *stat,
> > >                                      struct omap3isp_stat_data *data)
> > >     ...
> > >     buf = isp_stat_buf_get(stat, data);
> > > 
> > > static struct ispstat_buffer *isp_stat_buf_get(struct ispstat *stat,
> > >                                                struct omap3isp_stat_data *data)
> > > ...
> > >     if (buf->buf_size > data->buf_size) {
> > >             ...
> > >             return ERR_PTR(-EINVAL);
> > >     }
> > >     ...
> > >     rval = copy_to_user(data->buf,
> > >                         buf->virt_addr,
> > >                         buf->buf_size);
> > > 
> > > Regardless, additionally initialize data64 to be zero-filled to avoid
> > > undefined behavior.
> > > 
> > > Fixes: 378e3f81cb56 ("media: omap3isp: support 64-bit version of omap3isp_stat_data")
> > > Signed-off-by: Kees Cook <keescook@chromium.org>
> > > ---
> > >  drivers/media/platform/omap3isp/ispstat.c |  5 +--
> > >  include/uapi/linux/omap3isp.h             | 44 +++++++++++++++++------
> > >  2 files changed, 36 insertions(+), 13 deletions(-)
> > > 
> > > diff --git a/drivers/media/platform/omap3isp/ispstat.c b/drivers/media/platform/omap3isp/ispstat.c
> > > index 5b9b57f4d9bf..ea8222fed38e 100644
> > > --- a/drivers/media/platform/omap3isp/ispstat.c
> > > +++ b/drivers/media/platform/omap3isp/ispstat.c
> > > @@ -512,7 +512,7 @@ int omap3isp_stat_request_statistics(struct ispstat *stat,
> > >  int omap3isp_stat_request_statistics_time32(struct ispstat *stat,
> > >  					struct omap3isp_stat_data_time32 *data)
> > >  {
> > > -	struct omap3isp_stat_data data64;
> > > +	struct omap3isp_stat_data data64 = { };
> > >  	int ret;
> > >  
> > >  	ret = omap3isp_stat_request_statistics(stat, &data64);
> > > @@ -521,7 +521,8 @@ int omap3isp_stat_request_statistics_time32(struct ispstat *stat,
> > >  
> > >  	data->ts.tv_sec = data64.ts.tv_sec;
> > >  	data->ts.tv_usec = data64.ts.tv_usec;
> > > -	memcpy(&data->buf, &data64.buf, sizeof(*data) - sizeof(data->ts));
> > > +	data->buf = (uintptr_t)data64.buf;
> > > +	memcpy(&data->frame, &data64.buf, sizeof(data->frame));
> > >  
> > >  	return 0;
> > >  }
> > > diff --git a/include/uapi/linux/omap3isp.h b/include/uapi/linux/omap3isp.h
> > > index 87b55755f4ff..0a16af91621f 100644
> > > --- a/include/uapi/linux/omap3isp.h
> > > +++ b/include/uapi/linux/omap3isp.h
> > > @@ -159,13 +159,25 @@ struct omap3isp_h3a_aewb_config {
> > >  };
> > >  
> > >  /**
> > > - * struct omap3isp_stat_data - Statistic data sent to or received from user
> > > - * @ts: Timestamp of returned framestats.
> > > - * @buf: Pointer to pass to user.
> > > + * struct omap3isp_stat_frame - Statistic data without timestamp nor pointer.
> > > + * @buf_size: Size of buffer.
> > >   * @frame_number: Frame number of requested stats.
> > >   * @cur_frame: Current frame number being processed.
> > >   * @config_counter: Number of the configuration associated with the data.
> > >   */
> > > +struct omap3isp_stat_frame {
> > > +	__u32 buf_size;
> > > +	__u16 frame_number;
> > > +	__u16 cur_frame;
> > > +	__u16 config_counter;
> > > +};
> > > +
> > > +/**
> > > + * struct omap3isp_stat_data - Statistic data sent to or received from user
> > > + * @ts: Timestamp of returned framestats.
> > > + * @buf: Pointer to pass to user.
> > > + * @frame: Statistic data for frame.
> > > + */
> > >  struct omap3isp_stat_data {
> > >  #ifdef __KERNEL__
> > >  	struct {
> > > @@ -176,10 +188,15 @@ struct omap3isp_stat_data {
> > >  	struct timeval ts;
> > >  #endif
> > >  	void __user *buf;
> > > -	__u32 buf_size;
> > > -	__u16 frame_number;
> > > -	__u16 cur_frame;
> > > -	__u16 config_counter;
> > > +	union {
> > > +		struct {
> > > +			__u32 buf_size;
> > > +			__u16 frame_number;
> > > +			__u16 cur_frame;
> > > +			__u16 config_counter;
> > > +		};
> > > +		struct omap3isp_stat_frame frame;
> > > +	};
> > >  };
> > >  
> > >  #ifdef __KERNEL__
> > > @@ -189,10 +206,15 @@ struct omap3isp_stat_data_time32 {
> > >  		__s32	tv_usec;
> > >  	} ts;
> > >  	__u32 buf;
> > > -	__u32 buf_size;
> > > -	__u16 frame_number;
> > > -	__u16 cur_frame;
> > > -	__u16 config_counter;
> > > +	union {
> > > +		struct {
> > > +			__u32 buf_size;
> > > +			__u16 frame_number;
> > > +			__u16 cur_frame;
> > > +			__u16 config_counter;
> > > +		};
> > > +		struct omap3isp_stat_frame frame;
> > > +	};
> > >  };
> > >  #endif
> > >  

-- 
Regards,

Laurent Pinchart

Re: [PATCH] media: omap3isp: Extract struct group for memcpy() region

[Kees Cook]

On Thu, Jun 24, 2021 at 01:12:11AM +0300, Laurent Pinchart wrote:
> Hi Kees,
> 
> On Wed, Jun 16, 2021 at 09:22:23PM -0700, Kees Cook wrote:
> > On Wed, Jun 16, 2021 at 10:43:03PM +0300, Laurent Pinchart wrote:
> > > On Wed, Jun 16, 2021 at 11:59:38AM -0700, Kees Cook wrote:
> > > > Avoid writing past the end of a structure member by wrapping the target
> > > > region in a common named structure. This additionally fixes a
> > > > misalignment of the copy (since the size of "buf" changes between 64-bit
> > > > and 32-bit).
> > > 
> > > Could you have been mislead by the data64 name ? The difference between
> > > omap3isp_stat_data_time and omap3isp_stat_data_time32 is the size of the
> > > ts field, using 32-bit timestamps with legacy userspace, and 64-bit
> > > timestamps with more recent userspace. In both cases we're dealing with
> > > a 32-bit platform, as the omap3isp is not used in any 64-bit ARM SoC.
> > > The size of void __user *buf is thus 4 bytes in all cases, as is __u32
> > > buf.
> > 
> > Ah, yes, that's true. I was hitting this on arm64 builds
> > (CONFIG_COMPILE_TEST) where __user *buf is 64-bit. So, the "additionally
> > fixes" bit above is misleading in the sense that nothing was ever built
> > in the real world like that.
> > 
> > The patch still fixes the compile-time warnings, though.
> 
> I What's the compile-time warning ? I tried compiling the driver for
> ARM64 and didn't notice any.

Sorry, I didn't include the background well enough in the commit log,
but it's part of a tightening of memcpy() under FORTIFY_SOURCE and
also -Warray-bounds enablement. Here's what I've been saying on other
patches (this one was different because it seemed to be just broken
code):

  In preparation for FORTIFY_SOURCE performing compile-time and run-time
  field bounds checking for memcpy(), memmove(), and memset(), avoid
  intentionally writing across neighboring fields.

Anyway, I can carry this until the full series is posted, but I'm still
working through a few more fixes before I send the whole thing. This
patch was one of a handful that didn't have any series dependencies.

-Kees

-- 
Kees Cook