mainline inclusion
from mainline-v5.16-rc1
commit 7cd60e43
category: feature
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I590ZC
CVE: NA

Intel-SIG: commit 3aac3ebe x86/signal: Implement sigaltstack size validation.

--------------------------------

For historical reasons MINSIGSTKSZ is a constant which became already too
small with AVX512 support.

Add a mechanism to enforce strict checking of the sigaltstack size against
the real size of the FPU frame.

The strict check can be enabled via a config option and can also be
controlled via the kernel command line option 'strict_sas_size' independent
of the config switch.

Enabling it might break existing applications which allocate a too small
sigaltstack but 'work' because they never get a signal delivered. Though it
can be handy to filter out binaries which are not yet aware of
AT_MINSIGSTKSZ.

Also the upcoming support for dynamically enabled FPU features requires a
strict sanity check to ensure that:

   - Enabling of a dynamic feature, which changes the sigframe size fits
     into an enabled sigaltstack

   - Installing a too small sigaltstack after a dynamic feature has been
     added is not possible.

Implement the base check which is controlled by config and command line
options.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NChang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: NBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211021225527.10184-3-chang.seok.bae@intel.comSigned-off-by: NLin Wang <lin.x.wang@intel.com>