syzbot has found a NULL pointer dereference bug in fbcon [1].
This issue is caused by ops->putcs being a NULL pointer. We need to check the pointer before using it.
[1] https://syzkaller.appspot.com/bug?extid=3d613ae53c031502687a
Cc: stable@vger.kernel.org Reported-and-tested-by: syzbot+3d613ae53c031502687a@syzkaller.appspotmail.com Signed-off-by: Qianqiang Liu qianqiang.liu@163.com --- drivers/video/fbdev/core/fbcon.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 3f7333dca508..96c1262cc981 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -1284,7 +1284,7 @@ static void fbcon_putcs(struct vc_data *vc, const u16 *s, unsigned int count, struct fbcon_display *p = &fb_display[vc->vc_num]; struct fbcon_ops *ops = info->fbcon_par;
- if (!fbcon_is_inactive(vc, info)) + if (!fbcon_is_inactive(vc, info) && ops->putcs) ops->putcs(vc, info, s, count, real_y(p, ypos), xpos, get_color(vc, info, scr_readw(s), 1), get_color(vc, info, scr_readw(s), 0));
On 9/16/24 03:10, Qianqiang Liu wrote:
syzbot has found a NULL pointer dereference bug in fbcon [1].
This issue is caused by ops->putcs being a NULL pointer. We need to check the pointer before using it.
[1] https://syzkaller.appspot.com/bug?extid=3d613ae53c031502687a
Cc: stable@vger.kernel.org Reported-and-tested-by: syzbot+3d613ae53c031502687a@syzkaller.appspotmail.com Signed-off-by: Qianqiang Liu qianqiang.liu@163.com
drivers/video/fbdev/core/fbcon.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 3f7333dca508..96c1262cc981 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -1284,7 +1284,7 @@ static void fbcon_putcs(struct vc_data *vc, const u16 *s, unsigned int count, struct fbcon_display *p = &fb_display[vc->vc_num]; struct fbcon_ops *ops = info->fbcon_par;
- if (!fbcon_is_inactive(vc, info))
- if (!fbcon_is_inactive(vc, info) && ops->putcs)
I think this patch just hides the real problem. How could putcs have become NULL ?
Helge
ops->putcs(vc, info, s, count, real_y(p, ypos), xpos, get_color(vc, info, scr_readw(s), 1), get_color(vc, info, scr_readw(s), 0));
Hi,
I simplified the C reproducer as follows:
#include <stdint.h> #include <unistd.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <linux/fb.h> #include <linux/tiocl.h> #include <sys/ioctl.h>
struct param { uint8_t type; struct tiocl_selection ts; };
int main() { write(1, "executing program\n", sizeof("executing program\n") - 1);
int fd = open("/dev/fb1", 0, 0);
struct fb_con2fbmap con2fb; con2fb.console = 0x19; con2fb.framebuffer = 0; ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb);
int fd1 = open("/dev/tty1", O_RDWR, 0);
struct param param; param.type = 2; param.ts.xs = 0; param.ts.ys = 0; param.ts.xe = 0; param.ts.ye = 0; param.ts.sel_mode = 0;
ioctl(fd1, TIOCLINUX, ¶m);
con2fb.console = 1; con2fb.framebuffer = 0; ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb);
return 0; }
But I still need time to debug the kernel code..
linux-stable-mirror@lists.linaro.org
-
Helge Deller -
Qianqiang Liu