* Zheyu Ma <zheyuma97@xxxxxxxxx>:
> I found a minor in the smtcfb_read() function of the driver sm712fb.
>
> This read function can not handle the case that the size of the
> buffer is 3 and does not check for it, which may cause a page fault.
>
> The following log reveals it:
>
> [ 2432.614490] BUG: unable to handle page fault for address: ffffc90001ffffff
> [ 2432.618474] RIP: 0010:smtcfb_read+0x230/0x3e0
> [ 2432.626551] Call Trace:
> [ 2432.626770] <TASK>
> [ 2432.626950] vfs_read+0x198/0xa00
> [ 2432.627225] ? do_sys_openat2+0x27d/0x350
> [ 2432.627552] ? __fget_light+0x54/0x340
> [ 2432.627871] ksys_read+0xce/0x190
> [ 2432.628143] do_syscall_64+0x43/0x90
Could you try the attached patch ?
diff --git a/drivers/video/fbdev/sm712fb.c b/drivers/video/fbdev/sm712fb.c
index 0dbc6bf8268a..ab45212ccf66 100644
--- a/drivers/video/fbdev/sm712fb.c
+++ b/drivers/video/fbdev/sm712fb.c
@@ -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;
@@ -1059,25 +1059,11 @@ 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);
+ for (i = (c + 3) >> 2; i--;) {
+ u32 val = fb_readl(src++);
+ *dst = big_swap(val);
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;
