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.
Here is a simple PoC:
#include <endian.h> #include <fcntl.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/stat.h> #include <sys/syscall.h> #include <sys/types.h> #include <unistd.h>
int main(void) { char buf[10];
int fd = open("/dev/fb0", O_RDWR); read(fd, buf, 3);
return 0; }
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
Regards, Zheyu Ma
* Zheyu Ma zheyuma97@gmail.com:
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;
On Sat, Feb 26, 2022 at 11:03 PM Helge Deller deller@gmx.de wrote:
- Zheyu Ma zheyuma97@gmail.com:
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 ?
Good, the patch works for me, thanks.
Tested-by: Zheyu Ma zheyuma97@gmail.com
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;
Regards, Zheyu Ma
dri-devel@lists.freedesktop.org
-
Helge Deller -
Zheyu Ma