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Commit 478154be authored by Helge Deller's avatar Helge Deller Committed by Greg Kroah-Hartman
Browse files

video: fbdev: sm712fb: Fix crash in smtcfb_read() 



commit bd771cf5c4254511cc4abb88f3dab3bd58bdf8e8 upstream.

Zheyu Ma reported this crash in the sm712fb driver when reading
three bytes from the framebuffer:

 BUG: unable to handle page fault for address: ffffc90001ffffff
 RIP: 0010:smtcfb_read+0x230/0x3e0
 Call Trace:
  vfs_read+0x198/0xa00
  ? do_sys_openat2+0x27d/0x350
  ? __fget_light+0x54/0x340
  ksys_read+0xce/0x190
  do_syscall_64+0x43/0x90

Fix it by removing the open-coded endianess fixup-code and
by moving the pointer post decrement out the fb_readl() function.

Reported-by: default avatarZheyu Ma <zheyuma97@gmail.com>
Signed-off-by: default avatarHelge Deller <deller@gmx.de>
Tested-by: default avatarZheyu Ma <zheyuma97@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 67643b89

drivers/video/fbdev/sm712fb.c

+7 −18
Original line number Diff line number Diff line
@@ -1047,7 +1047,7 @@ static ssize_t smtcfb_read(struct fb_info *info, char __user *buf, 
	if (count + p > total_size)

		count = total_size - p;



	buffer = kmalloc((count > PAGE_SIZE) ? PAGE_SIZE : count, GFP_KERNEL);

	buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);

	if (!buffer)

		return -ENOMEM;
@@ -1059,24 +1059,13 @@ static ssize_t smtcfb_read(struct fb_info *info, char __user *buf, 
	while (count) {

		c = (count > PAGE_SIZE) ? PAGE_SIZE : count;

		dst = buffer;

		for (i = c >> 2; i--;) {

			*dst = fb_readl(src++);

			*dst = big_swap(*dst);

			dst++;

		}

		if (c & 3) {

			u8 *dst8 = (u8 *)dst;

			u8 __iomem *src8 = (u8 __iomem *)src;

		for (i = (c + 3) >> 2; i--;) {

			u32 val;



			for (i = c & 3; i--;) {

				if (i & 1) {

					*dst8++ = fb_readb(++src8);

				} else {

					*dst8++ = fb_readb(--src8);

					src8 += 2;

				}

			}

			src = (u32 __iomem *)src8;

			val = fb_readl(src);

			*dst = big_swap(val);

			src++;

			dst++;

		}



		if (copy_to_user(buf, buffer, c)) {