Cc'ing Grzegorz. On Tue, May 21, 2019 at 11:21:18AM +0800, Gen Zhang wrote: > On Mon, May 20, 2019 at 10:55:40PM -0400, Nicolas Pitre wrote: > > As soon as you release the lock, another thread could come along and > > start using the memory pointed by vc_cons[currcons].d you're about to > > free here. This is unlikely for an initcall, but still. > > > > You should consider this ordering instead: > > > > err_vc_screenbuf: > > kfree(vc); > > vc_cons[currcons].d = NULL; > > err_vc: > > console_unlock(); > > return -ENOMEM; > In function con_init(), the pointer variable vc_cons[currcons].d, vc and > vc->vc_screenbuf is allocated a memory space via kzalloc(). And they are > used in the following codes. > However, when there is a memory allocation error, kzalloc() can fail. > Thus null pointer (vc_cons[currcons].d, vc and vc->vc_screenbuf) > dereference may happen. And it will cause the kernel to crash. Therefore, > we should check return value and handle the error. > Further,the loop condition MIN_NR_CONSOLES is defined as 1 in > include/uapi/linux/vt.h and it is not changed. So there is no need to > unwind the loop. > > Signed-off-by: Gen Zhang <blackgod016...@gmail.com> > > --- > diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c > index fdd12f8..ea47eb3 100644 > --- a/drivers/tty/vt/vt.c > +++ b/drivers/tty/vt/vt.c > @@ -3350,10 +3350,14 @@ static int __init con_init(void) > > for (currcons = 0; currcons < MIN_NR_CONSOLES; currcons++) { > vc_cons[currcons].d = vc = kzalloc(sizeof(struct vc_data), > GFP_NOWAIT); > + if (!vc) > + goto err_vc; > INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK); > tty_port_init(&vc->port); > visual_init(vc, currcons, 1); > vc->vc_screenbuf = kzalloc(vc->vc_screenbuf_size, GFP_NOWAIT); > + if (!vc->vc_screenbuf) > + goto err_vc_screenbuf; > vc_init(vc, vc->vc_rows, vc->vc_cols, > currcons || !vc->vc_sw->con_save_screen); > } > @@ -3375,6 +3379,13 @@ static int __init con_init(void) > register_console(&vt_console_driver); > #endif > return 0; > +err_vc_screenbuf: > + kfree(vc); > + vc_cons[currcons].d = NULL; > +err_vc: > + console_unlock(); > + return -ENOMEM; > + > } > console_initcall(con_init); > ---
-- Best regards, Oleksandr Natalenko (post-factum) Senior Software Maintenance Engineer