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Date: Tue, 28 Jul 2020 07:52:10 -0400 From: Peilin Ye <yepeilin.cs@...il.com> To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de> Cc: Peilin Ye <yepeilin.cs@...il.com>, David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>, Dan Carpenter <dan.carpenter@...cle.com>, Arnd Bergmann <arnd@...db.de>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, linux-kernel-mentees@...ts.linuxfoundation.org, dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org Subject: [Linux-kernel-mentees] [PATCH v2] drm/bufs: Prevent kernel-infoleak in copy_one_buf() Currently `struct drm_buf_desc` is defined as follows: struct drm_buf_desc { int count; int size; int low_mark; int high_mark; enum { _DRM_PAGE_ALIGN = 0x01, _DRM_AGP_BUFFER = 0x02, _DRM_SG_BUFFER = 0x04, _DRM_FB_BUFFER = 0x08, _DRM_PCI_BUFFER_RO = 0x10 } flags; unsigned long agp_start; }; copy_one_buf() is potentially copying uninitialized kernel stack memory to userspace, since the compiler may leave such "holes" (around `.flags` and `.agp_start` fields) in this statically allocated structure. Prevent it by initializing `v` with memset(). Cc: stable@...r.kernel.org Fixes: 5c7640ab6258 ("switch compat_drm_infobufs() to drm_ioctl_kernel()") Suggested-by: Dan Carpenter <dan.carpenter@...cle.com> Acked-by: Arnd Bergmann <arnd@...db.de> Signed-off-by: Peilin Ye <yepeilin.cs@...il.com> --- Change in v2: - Improve commit description. (Suggested by Arnd Bergmann <arnd@...db.de>) drivers/gpu/drm/drm_bufs.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/drm_bufs.c b/drivers/gpu/drm/drm_bufs.c index a0735fbc144b..f99cd4a3f951 100644 --- a/drivers/gpu/drm/drm_bufs.c +++ b/drivers/gpu/drm/drm_bufs.c @@ -1349,10 +1349,14 @@ static int copy_one_buf(void *data, int count, struct drm_buf_entry *from) { struct drm_buf_info *request = data; struct drm_buf_desc __user *to = &request->list[count]; - struct drm_buf_desc v = {.count = from->buf_count, - .size = from->buf_size, - .low_mark = from->low_mark, - .high_mark = from->high_mark}; + struct drm_buf_desc v; + + memset(&v, 0, sizeof(v)); + + v.count = from->buf_count; + v.size = from->buf_size; + v.low_mark = from->low_mark; + v.high_mark = from->high_mark; if (copy_to_user(to, &v, offsetof(struct drm_buf_desc, flags))) return -EFAULT; -- 2.25.1
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