[Linux-kernel-mentees] [PATCH] drm/bufs: Prevent kernel-infoleak in copy_one_buf()

From: Peilin Ye <yepeilin.cs@gmail.com>
To: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>,
	Thomas Zimmermann <tzimmermann@suse.de>
Cc: Arnd Bergmann <arnd@arndb.de>, David Airlie <airlied@linux.ie>,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	Daniel Vetter <daniel@ffwll.ch>,
	linux-kernel-mentees@lists.linuxfoundation.org,
	Peilin Ye <yepeilin.cs@gmail.com>,
	Dan Carpenter <dan.carpenter@oracle.com>
Subject: [Linux-kernel-mentees] [PATCH] drm/bufs: Prevent kernel-infoleak in copy_one_buf()
Date: Mon, 27 Jul 2020 21:43:43 -0400	[thread overview]
Message-ID: <20200728014343.341303-1-yepeilin.cs@gmail.com> (raw)

copy_one_buf() is copying uninitialized stack memory to userspace due to
the compiler not initializing holes in statically allocated structures.
Fix it by initializing `v` with memset().

Cc: stable@vger.kernel.org
Fixes: 5c7640ab6258 ("switch compat_drm_infobufs() to drm_ioctl_kernel()")
Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
---
 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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