linux-kernel - [Linux-kernel-mentees] [PATCH] drm/bufs: Prevent kernel-infoleak in copy_one

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Message-Id: <20200728014343.341303-1-yepeilin.cs@gmail.com>
Date:   Mon, 27 Jul 2020 21:43:43 -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] drm/bufs: Prevent kernel-infoleak in copy_one_buf()

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@...r.kernel.org
Fixes: 5c7640ab6258 ("switch compat_drm_infobufs() to drm_ioctl_kernel()")
Suggested-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Peilin Ye <yepeilin.cs@...il.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