array_index_nospec ensures that an out-of-bounds value is set to zero
on the transient path. Decreasing the value by one afterwards causes
a transient integer underflow. vsa.console should be decreased first
and then sanitized with array_index_nospec.
Kasper Acknowledgements: Jakob Koschel, Brian Johannesmeyer, Kaveh
Razavi, Herbert Bos, Cristiano Giuffrida from the VUSec group at VU
Amsterdam.
Co-developed-by: Brian Johannesmeyer <[email protected]>
Signed-off-by: Brian Johannesmeyer <[email protected]>
Signed-off-by: Jakob Koschel <[email protected]>
---
drivers/tty/vt/vt_ioctl.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
index 3639bb6dc372..e0714a9c9fd7 100644
--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -599,8 +599,8 @@ static int vt_setactivate(struct vt_setactivate __user *sa)
if (vsa.console == 0 || vsa.console > MAX_NR_CONSOLES)
return -ENXIO;
- vsa.console = array_index_nospec(vsa.console, MAX_NR_CONSOLES + 1);
vsa.console--;
+ vsa.console = array_index_nospec(vsa.console, MAX_NR_CONSOLES);
console_lock();
ret = vc_allocate(vsa.console);
if (ret) {
--
2.25.1
in vt_setactivate an almost identical code path has been patched
with array_index_nospec. In the VT_ACTIVATE path the user input
is from a system call argument instead of a usercopy.
For consistency both code paths should have the same mitigations
applied.
Kasper Acknowledgements: Jakob Koschel, Brian Johannesmeyer, Kaveh
Razavi, Herbert Bos, Cristiano Giuffrida from the VUSec group at VU
Amsterdam.
Co-developed-by: Brian Johannesmeyer <[email protected]>
Signed-off-by: Brian Johannesmeyer <[email protected]>
Signed-off-by: Jakob Koschel <[email protected]>
---
drivers/tty/vt/vt_ioctl.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
index e0714a9c9fd7..58013698635f 100644
--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -845,6 +845,7 @@ int vt_ioctl(struct tty_struct *tty,
return -ENXIO;
arg--;
+ arg = array_index_nospec(arg, MAX_NR_CONSOLES);
console_lock();
ret = vc_allocate(arg);
console_unlock();
--
2.25.1