lkml.org 
[lkml]   [2019]   [May]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH v3] vt: Fix a missing-check bug in drivers/tty/vt/vt.c
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 <blackgod016574@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);
---
\
 
 \ /
  Last update: 2019-05-21 05:21    [W:0.085 / U:59.376 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site