tty: vt: always invoke vc->vc_sw->con_resize callback
commit ffb324e6f8
upstream.
syzbot is reporting OOB write at vga16fb_imageblit() [1], for
resize_screen() from ioctl(VT_RESIZE) returns 0 without checking whether
requested rows/columns fit the amount of memory reserved for the graphical
screen if current mode is KD_GRAPHICS.
----------
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/kd.h>
#include <linux/vt.h>
int main(int argc, char *argv[])
{
const int fd = open("/dev/char/4:1", O_RDWR);
struct vt_sizes vt = { 0x4100, 2 };
ioctl(fd, KDSETMODE, KD_GRAPHICS);
ioctl(fd, VT_RESIZE, &vt);
ioctl(fd, KDSETMODE, KD_TEXT);
return 0;
}
----------
Allow framebuffer drivers to return -EINVAL, by moving vc->vc_mode !=
KD_GRAPHICS check from resize_screen() to fbcon_resize().
Link: https://syzkaller.appspot.com/bug?extid=1f29e126cf461c4de3b3 [1]
Reported-by: syzbot <syzbot+1f29e126cf461c4de3b3@syzkaller.appspotmail.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Tested-by: syzbot <syzbot+1f29e126cf461c4de3b3@syzkaller.appspotmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
pull/356/head^2
parent
a14ca25d4f
commit
eb46907f99
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@ -1172,7 +1172,7 @@ static inline int resize_screen(struct vc_data *vc, int width, int height,
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/* Resizes the resolution of the display adapater */
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int err = 0;
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if (vc->vc_mode != KD_GRAPHICS && vc->vc_sw->con_resize)
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if (vc->vc_sw->con_resize)
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err = vc->vc_sw->con_resize(vc, width, height, user);
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return err;
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@ -2031,7 +2031,7 @@ static int fbcon_resize(struct vc_data *vc, unsigned int width,
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return -EINVAL;
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DPRINTK("resize now %ix%i\n", var.xres, var.yres);
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if (con_is_visible(vc)) {
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if (con_is_visible(vc) && vc->vc_mode == KD_TEXT) {
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var.activate = FB_ACTIVATE_NOW |
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FB_ACTIVATE_FORCE;
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fb_set_var(info, &var);
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