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e9c38f9fc2
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 2a35d196c1 ("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>
23 lines
1.2 KiB
Text
23 lines
1.2 KiB
Text
What: /sys/fs/selinux/checkreqprot
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Date: April 2005 (predates git)
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KernelVersion: 2.6.12-rc2 (predates git)
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Contact: selinux@vger.kernel.org
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Description:
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The selinuxfs "checkreqprot" node allows SELinux to be configured
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to check the protection requested by userspace for mmap/mprotect
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calls instead of the actual protection applied by the kernel.
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This was a compatibility mechanism for legacy userspace and
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for the READ_IMPLIES_EXEC personality flag. However, if set to
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1, it weakens security by allowing mappings to be made executable
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without authorization by policy. The default value of checkreqprot
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at boot was changed starting in Linux v4.4 to 0 (i.e. check the
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actual protection), and Android and Linux distributions have been
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explicitly writing a "0" to /sys/fs/selinux/checkreqprot during
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initialization for some time. Support for setting checkreqprot to 1
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will be removed in a future kernel release, at which point the kernel
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will always cease using checkreqprot internally and will always
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check the actual protections being applied upon mmap/mprotect calls.
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The checkreqprot selinuxfs node will remain for backward compatibility
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but will discard writes of the "0" value and will reject writes of the
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"1" value when this mechanism is removed.
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