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Commit e97267cb authored by Gustavo A. R. Silva's avatar Gustavo A. R. Silva Committed by Greg Kroah-Hartman
Browse files

tty: vt_ioctl: fix potential Spectre v1 

vsa.console is indirectly controlled by user-space, hence leading to
a potential exploitation of the Spectre variant 1 vulnerability.

This issue was detected with the help of Smatch:

drivers/tty/vt/vt_ioctl.c:711 vt_ioctl() warn: potential spectre issue
'vc_cons' [r]

Fix this by sanitizing vsa.console before using it to index vc_cons

Notice that given that speculation windows are large, the policy is
to kill the speculation on the first load and not worry if it can be
completed with a dependent load/store [1].

[1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2



Cc: stable@vger.kernel.org
Signed-off-by: default avatarGustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: default avatarAlan Cox <alan@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent fe324167

drivers/tty/vt/vt_ioctl.c

+4 −0
Original line number Diff line number Diff line
@@ -32,6 +32,8 @@ 
#include <asm/io.h>

#include <linux/uaccess.h>



#include <linux/nospec.h>



#include <linux/kbd_kern.h>

#include <linux/vt_kern.h>

#include <linux/kbd_diacr.h>
@@ -700,6 +702,8 @@ int vt_ioctl(struct tty_struct *tty, 
		if (vsa.console == 0 || vsa.console > MAX_NR_CONSOLES)

			ret = -ENXIO;

		else {

			vsa.console = array_index_nospec(vsa.console,

							 MAX_NR_CONSOLES + 1);

			vsa.console--;

			console_lock();

			ret = vc_allocate(vsa.console);