Merge branch 'for-4.20' of https://git.kernel.org/pub/scm/linux/kernel/git/broonie...

[sfrench/cifs-2.6.git] / Documentation / sysctl / kernel.txt

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 37a679501ddc68bc0ab26c58444794c0d30c8f40..1b8775298cf7a0223c04aa7098cf1d1e4d24fefd 100644 (file)
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -89,6 +89,7 @@ show up in /proc/sys/kernel:
 - shmmni
 - softlockup_all_cpu_backtrace
 - soft_watchdog
+- stack_erasing
 - stop-a                      [ SPARC only ]
 - sysrq                       ==> Documentation/admin-guide/sysrq.rst
 - sysctl_writes_strict
@@ -987,6 +988,23 @@ detect a hard lockup condition.
 
 ==============================================================
 
+stack_erasing
+
+This parameter can be used to control kernel stack erasing at the end
+of syscalls for kernels built with CONFIG_GCC_PLUGIN_STACKLEAK.
+
+That erasing reduces the information which kernel stack leak bugs
+can reveal and blocks some uninitialized stack variable attacks.
+The tradeoff is the performance impact: on a single CPU system kernel
+compilation sees a 1% slowdown, other systems and workloads may vary.
+
+  0: kernel stack erasing is disabled, STACKLEAK_METRICS are not updated.
+
+  1: kernel stack erasing is enabled (default), it is performed before
+     returning to the userspace at the end of syscalls.
+
+==============================================================
+
 tainted:
 
 Non-zero if the kernel has been tainted. Numeric values, which can be