Re: [PATCH] fbdev/omapfb: fix omapfb_memory_read infoleak
From: Kees Cook <hidden>
Date: 2018-09-12 22:38:30
Also in:
stable
On Wed, Sep 12, 2018 at 12:30 AM, Tomi Valkeinen [off-list ref] wrote:
quoted hunk ↗ jump to hunk
OMAPFB_MEMORY_READ ioctl reads pixels from the LCD's memory and copies them to a userspace buffer. The code has two issues: - The user provided width and height could be large enough to overflow the calculations - The copy_to_user() can copy uninitialized memory to the userspace, which might contain sensitive kernel information. Fix these by limiting the width & height parameters, and only copying the amount of data that we actually received from the LCD. Signed-off-by: Tomi Valkeinen <redacted> Reported-by: Jann Horn <jannh@google.com> Cc: stable@vger.kernel.org Cc: security@kernel.org Cc: Will Deacon <redacted> Cc: Jann Horn <jannh@google.com> Cc: Tony Lindgren <tony@atomide.com> --- drivers/video/fbdev/omap2/omapfb/omapfb-ioctl.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)diff --git a/drivers/video/fbdev/omap2/omapfb/omapfb-ioctl.c b/drivers/video/fbdev/omap2/omapfb/omapfb-ioctl.c index ef69273074ba..a3edb20ea4c3 100644 --- a/drivers/video/fbdev/omap2/omapfb/omapfb-ioctl.c +++ b/drivers/video/fbdev/omap2/omapfb/omapfb-ioctl.c@@ -496,6 +496,9 @@ static int omapfb_memory_read(struct fb_info *fbi, if (!access_ok(VERIFY_WRITE, mr->buffer, mr->buffer_size)) return -EFAULT; + if (mr->w > 4096 || mr->h > 4096) + return -EINVAL; + if (mr->w * mr->h * 3 > mr->buffer_size) return -EINVAL;
alternatively, replace the above two tests with:
alloc_size = array3_size(mr->w, mr->h, 3);
if (alloc_size > mr->buffer_size)
return -EINVAL;
buf = vmalloc(alloc_size);
...
quoted hunk ↗ jump to hunk
@@ -509,7 +512,7 @@ static int omapfb_memory_read(struct fb_info *fbi, mr->x, mr->y, mr->w, mr->h); if (r > 0) { - if (copy_to_user(mr->buffer, buf, mr->buffer_size)) + if (copy_to_user(mr->buffer, buf, r))
But yes, this seems correct regardless: userspace was being overwritten beyond "r", potentially. -Kees
r = -EFAULT;
}
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