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SubjectRe: [PATCH] tty: vt: initialize unicode screen buffer
From
On 19. 07. 22, 7:49, Tetsuo Handa wrote:
> syzbot reports kernel infoleak at vcs_read() [1], for buffer can be read
> immediately after resize operation. Initialize buffer using kzalloc().
>
> ----------
> #include <fcntl.h>
> #include <unistd.h>
> #include <sys/ioctl.h>
> #include <linux/fb.h>
>
> int main(int argc, char *argv[])
> {
> struct fb_var_screeninfo var = { };
> const int fb_fd = open("/dev/fb0", 3);
> ioctl(fb_fd, FBIOGET_VSCREENINFO, &var);
> var.yres = 0x21;
> ioctl(fb_fd, FBIOPUT_VSCREENINFO, &var);
> return read(open("/dev/vcsu", O_RDONLY), &var, sizeof(var)) == -1;
> }
> ----------
>
> Link: https://syzkaller.appspot.com/bug?extid=31a641689d43387f05d3 [1]
> Reported-by: syzbot <syzbot+31a641689d43387f05d3@syzkaller.appspotmail.com>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

Yes, it makes sense.

Reviewed-by: Jiri Slaby <jirislaby@kernel.org>

> ---
> drivers/tty/vt/vt.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
> index f8c87c4d7399..6968517d6f8b 100644
> --- a/drivers/tty/vt/vt.c
> +++ b/drivers/tty/vt/vt.c
> @@ -344,7 +344,7 @@ static struct uni_screen *vc_uniscr_alloc(unsigned int cols, unsigned int rows)
> /* allocate everything in one go */
> memsize = cols * rows * sizeof(char32_t);
> memsize += rows * sizeof(char32_t *);
> - p = vmalloc(memsize);
> + p = vzalloc(memsize);
> if (!p)
> return NULL;
>

thanks,
--
js
suse labs

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