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authorStephen Smalley <sds@tycho.nsa.gov>2020-01-08 11:24:47 -0500
committerPaul Moore <paul@paul-moore.com>2020-02-10 10:49:01 -0500
commite9c38f9fc2ccd31befe1bb1605b69213483a15b7 (patch)
tree281e142f528909787ffc92dab94acfc0593d9474 /Documentation/ABI/obsolete
parent4b36cb773a8153417a080f8025d522322f915aea (diff)
Documentation,selinux: deprecate setting checkreqprot to 1
Deprecate setting the SELinux checkreqprot tunable to 1 via kernel parameter or /sys/fs/selinux/checkreqprot. Setting it to 0 is left intact for compatibility since Android and some Linux distributions do so for security and treat an inability to set it as a fatal error. Eventually setting it to 0 will become a no-op and the kernel will stop using checkreqprot's value internally altogether. checkreqprot was originally introduced as a compatibility mechanism for legacy userspace and the READ_IMPLIES_EXEC personality flag. However, if set to 1, it weakens security by allowing mappings to be made executable without authorization by policy. The default value for the SECURITY_SELINUX_CHECKREQPROT_VALUE config option was changed from 1 to 0 in commit 2a35d196c160e3 ("selinux: change CONFIG_SECURITY_SELINUX_CHECKREQPROT_VALUE default") and both Android and Linux distributions began explicitly setting /sys/fs/selinux/checkreqprot to 0 some time ago. Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> Signed-off-by: Paul Moore <paul@paul-moore.com>
Diffstat (limited to 'Documentation/ABI/obsolete')
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diff --git a/Documentation/ABI/obsolete/sysfs-selinux-checkreqprot b/Documentation/ABI/obsolete/sysfs-selinux-checkreqprot
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@@ -0,0 +1,23 @@
+What: /sys/fs/selinux/checkreqprot
+Date: April 2005 (predates git)
+KernelVersion: 2.6.12-rc2 (predates git)
+Contact: selinux@vger.kernel.org
+Description:
+
+ The selinuxfs "checkreqprot" node allows SELinux to be configured
+ to check the protection requested by userspace for mmap/mprotect
+ calls instead of the actual protection applied by the kernel.
+ This was a compatibility mechanism for legacy userspace and
+ for the READ_IMPLIES_EXEC personality flag. However, if set to
+ 1, it weakens security by allowing mappings to be made executable
+ without authorization by policy. The default value of checkreqprot
+ at boot was changed starting in Linux v4.4 to 0 (i.e. check the
+ actual protection), and Android and Linux distributions have been
+ explicitly writing a "0" to /sys/fs/selinux/checkreqprot during
+ initialization for some time. Support for setting checkreqprot to 1
+ will be removed in a future kernel release, at which point the kernel
+ will always cease using checkreqprot internally and will always
+ check the actual protections being applied upon mmap/mprotect calls.
+ The checkreqprot selinuxfs node will remain for backward compatibility
+ but will discard writes of the "0" value and will reject writes of the
+ "1" value when this mechanism is removed.