On 3/2/22 15:33, Zheyu Ma wrote:

When the sm712fb driver writes three bytes to the framebuffer, the driver will crash:

BUG: unable to handle page fault for address: ffffc90001ffffff
RIP: 0010:smtcfb_write+0x454/0x5b0
Call Trace:
 vfs_write+0x291/0xd60
 ? do_sys_openat2+0x27d/0x350
 ? __fget_light+0x54/0x340
 ksys_write+0xce/0x190
 do_syscall_64+0x43/0x90
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Fix it by removing the open-coded endianness fixup-code.

Signed-off-by: Zheyu Ma zheyuma97@gmail.com

Thanks... it's already in the fbdev git tree and queued up for v5.18... https://git.kernel.org/pub/scm/linux/kernel/git/deller/linux-fbdev.git/commi...

Helge

---

drivers/video/fbdev/sm712fb.c | 21 ++++----------------- 1 file changed, 4 insertions(+), 17 deletions(-)

diff --git a/drivers/video/fbdev/sm712fb.c b/drivers/video/fbdev/sm712fb.c index 0dbc6bf8268a..e355089ac7d6 100644 --- a/drivers/video/fbdev/sm712fb.c +++ b/drivers/video/fbdev/sm712fb.c @@ -1130,7 +1130,7 @@ static ssize_t smtcfb_write(struct fb_info *info, const char __user *buf, count = total_size - p; }

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

• buffer = kmalloc(PAGE_SIZE, GFP_KERNEL); if (!buffer) return -ENOMEM;

@@ -1148,24 +1148,11 @@ static ssize_t smtcfb_write(struct fb_info *info, const char __user *buf, break; }

• for (i = c >> 2; i--;) {
  

• 	fb_writel(big_swap(*src), dst++);
  

• for (i = (c + 3) >> 2; i--;) {
  

• 	fb_writel(big_swap(*src), dst);
  

• 	dst++;
  src++;
  

  }

• if (c & 3) {
  

• 	u8 *src8 = (u8 *)src;
  

• 	u8 __iomem *dst8 = (u8 __iomem *)dst;
  

• 	for (i = c & 3; i--;) {
  

• 		if (i & 1) {
  

• 			fb_writeb(*src8++, ++dst8);
  

• 		} else {
  

• 			fb_writeb(*src8++, --dst8);
  

• 			dst8 += 2;
  

• 		}
  

• 	}
  

• 	dst = (u32 __iomem *)dst8;
  

• }
  
  

  *ppos += c; buf += c;