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vt_ioctl: fix array_index_nospec in vt_setactivate

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commit 61cc70d9e8ef5b042d4ed87994d20100ec8896d9 upstream.

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 <bjohannesmeyer@gmail.com>
Signed-off-by: Brian Johannesmeyer <bjohannesmeyer@gmail.com>
Signed-off-by: Jakob Koschel <jakobkoschel@gmail.com>
Link: https://lore.kernel.org/r/20220127144406.3589293-1-jakobkoschel@gmail.com
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jakob Koschel
2022-01-27 15:44:04 +01:00
committed by Greg Kroah-Hartman
parent 22249886dc
commit 778302ca09
1 changed files with 1 additions and 1 deletions
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2
drivers/tty/vt/vt_ioctl.c
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@@ -699,8 +699,8 @@ static int vt_setactivate(struct vt_setactivate __user *sa)
if (vsa.console == 0 || vsa.console > MAX_NR_CONSOLES) if (vsa.console == 0 || vsa.console > MAX_NR_CONSOLES)
return -ENXIO; return -ENXIO;
vsa.console = array_index_nospec(vsa.console, MAX_NR_CONSOLES + 1);
vsa.console--; vsa.console--;
vsa.console = array_index_nospec(vsa.console, MAX_NR_CONSOLES);
console_lock(); console_lock();
ret = vc_allocate(vsa.console); ret = vc_allocate(vsa.console);
if (ret) { if (ret) {