Mailing List Archive: [PATCH] drivers/media/video/ivtv/ivtvfb.c: prevent reading uninitialized stack memory

The FBIOGET_VBLANK device ioctl allows unprivileged users to read 16
bytes of uninitialized stack memory, because the "reserved" member of
the fb_vblank struct declared on the stack is not altered or zeroed
before being copied back to the user. This patch takes care of it.

Signed-off-by: Dan Rosenberg <dan.j.rosenberg@gmail.com>

--- linux-2.6.35.4.orig/drivers/media/video/ivtv/ivtvfb.c 2010-08-26 19:47:12.000000000 -0400
+++ linux-2.6.35.4/drivers/media/video/ivtv/ivtvfb.c 2010-09-15 14:16:46.797375399 -0400
@@ -458,6 +458,8 @@ static int ivtvfb_ioctl(struct fb_info *
struct fb_vblank vblank;
u32 trace;

+ memset(&vblank, 0, sizeof(struct fb_vblank));
+
vblank.flags = FB_VBLANK_HAVE_COUNT |FB_VBLANK_HAVE_VCOUNT |
FB_VBLANK_HAVE_VSYNC;
trace = read_reg(IVTV_REG_DEC_LINE_FIELD) >> 16;

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Acked-by: Andy Walls <awalls@md.metrocast.net>

By tomorrow evening I'll put this in my repo and ask for Mauro to pull it.

Regards,
Andy

Dan Rosenberg <drosenberg@vsecurity.com> wrote:

>The FBIOGET_VBLANK device ioctl allows unprivileged users to read 16
>bytes of uninitialized stack memory, because the "reserved" member of
>the fb_vblank struct declared on the stack is not altered or zeroed
>before being copied back to the user. This patch takes care of it.
>
>Signed-off-by: Dan Rosenberg <dan.j.rosenberg@gmail.com>
>
>--- linux-2.6.35.4.orig/drivers/media/video/ivtv/ivtvfb.c 2010-08-26 19:47:12.000000000 -0400
>+++ linux-2.6.35.4/drivers/media/video/ivtv/ivtvfb.c 2010-09-15 14:16:46.797375399 -0400
>@@ -458,6 +458,8 @@ static int ivtvfb_ioctl(struct fb_info *
> struct fb_vblank vblank;
> u32 trace;
>
>+ memset(&vblank, 0, sizeof(struct fb_vblank));
>+
> vblank.flags = FB_VBLANK_HAVE_COUNT |FB_VBLANK_HAVE_VCOUNT |
> FB_VBLANK_HAVE_VSYNC;
> trace = read_reg(IVTV_REG_DEC_LINE_FIELD) >> 16;
>
>
>
>
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