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ebfdfeeae8
vgacon_scrollback_update() always leaves enbough room in the scrollback
buffer for the next call, but if the console size changed that room
might not actually be enough, and so we need to re-check.
The check should be in the loop since vgacon_scrollback_cur->tail is
updated in the loop and count may be more than 1 when triggered by CSI M,
as Jiri's PoC:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <fcntl.h>
int main(int argc, char** argv)
{
int fd = open("/dev/tty1", O_RDWR);
unsigned short size[3] = {25, 200, 0};
ioctl(fd, 0x5609, size); // VT_RESIZE
write(fd, "\e[1;1H", 6);
for (int i = 0; i < 30; i++)
write(fd, "\e[10M", 5);
}
It leads to various crashes as vgacon_scrollback_update writes out of
the buffer:
BUG: unable to handle page fault for address: ffffc900001752a0
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
RIP: 0010:mutex_unlock+0x13/0x30
...
Call Trace:
n_tty_write+0x1a0/0x4d0
tty_write+0x1a0/0x2e0
Or to KASAN reports:
BUG: KASAN: slab-out-of-bounds in vgacon_scroll+0x57a/0x8ed
This fixes CVE-2020-14331.
Reported-by: 张云海 <zhangyunhai@nsfocus.com>
Reported-by: Yang Yingliang <yangyingliang@huawei.com>
Reported-by: Kyungtae Kim <kt0755@gmail.com>
Fixes:
|
||
|---|---|---|
| .. | ||
| backlight | ||
| console | ||
| fbdev | ||
| logo | ||
| display_timing.c | ||
| hdmi.c | ||
| Kconfig | ||
| Makefile | ||
| of_display_timing.c | ||
| of_videomode.c | ||
| vgastate.c | ||
| videomode.c | ||