[01/64] media: omap3isp: Extract struct group for memcpy() region

Message ID 20210727205855.411487-2-keescook@chromium.org
State New
Headers show
Series
  • Introduce strict memcpy() bounds checking
Related show

Commit Message

Kees Cook July 27, 2021, 8:57 p.m.
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.  Wrap the target region
in a common named structure. This additionally fixes a theoretical
misalignment of the copy (since the size of "buf" changes between 64-bit
and 32-bit, but this is likely never built for 64-bit).

FWIW, I think this code is totally broken on 64-bit (which appears to
not be a "real" build configuration): 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(-)

Comments

David Sterba July 28, 2021, 8:59 a.m. | #1
On Tue, Jul 27, 2021 at 01:57:52PM -0700, Kees Cook wrote:
> 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.  Wrap the target region
> in a common named structure. This additionally fixes a theoretical
> misalignment of the copy (since the size of "buf" changes between 64-bit
> and 32-bit, but this is likely never built for 64-bit).
> 
> FWIW, I think this code is totally broken on 64-bit (which appears to
> not be a "real" build configuration): 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 = { };

Should this be { 0 } ?

We've seen patches trying to switch from { 0 } to {  } but the answer
was that { 0 } is supposed to be used,
http://www.ex-parrot.com/~chris/random/initialise.html

(from https://lore.kernel.org/lkml/fbddb15a-6e46-3f21-23ba-b18f66e3448a@suse.com/)

Patch

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