From: Helge Deller deller@gmx.de
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: Zheyu Ma zheyuma97@gmail.com Signed-off-by: Helge Deller deller@gmx.de Tested-by: Zheyu Ma zheyuma97@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/video/fbdev/sm712fb.c | 25 +++++++------------------ 1 file changed, 7 insertions(+), 18 deletions(-)
--- a/drivers/video/fbdev/sm712fb.c +++ b/drivers/video/fbdev/sm712fb.c @@ -1046,7 +1046,7 @@ static ssize_t smtcfb_read(struct fb_inf 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;
@@ -1058,25 +1058,14 @@ static ssize_t smtcfb_read(struct fb_inf while (count) { c = (count > PAGE_SIZE) ? PAGE_SIZE : count; dst = buffer; - for (i = c >> 2; i--;) { - *dst = fb_readl(src++); - *dst = big_swap(*dst); + for (i = (c + 3) >> 2; i--;) { + u32 val; + + val = fb_readl(src); + *dst = big_swap(val); + src++; dst++; } - if (c & 3) { - u8 *dst8 = (u8 *)dst; - u8 __iomem *src8 = (u8 __iomem *)src; - - for (i = c & 3; i--;) { - if (i & 1) { - *dst8++ = fb_readb(++src8); - } else { - *dst8++ = fb_readb(--src8); - src8 += 2; - } - } - src = (u32 __iomem *)src8; - }
if (copy_to_user(buf, buffer, c)) { err = -EFAULT;