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We originally promised that the SELinux 'checkreqprot' functionality would be removed no sooner than June 2021, and now that it is March 2023 it seems like it is a good time to do the final removal. The deprecation notice in the kernel provides plenty of detail on why 'checkreqprot' is not desirable, with the key point repeated below: 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. Along with the official deprecation notice, we have been discussing this on-list and directly with several of the larger SELinux-based distros and everyone is happy to see this feature finally removed. In an attempt to catch all of the smaller, and DIY, Linux systems we have been writing a deprecation notice URL into the kernel log, along with a growing ssleep() penalty, when admins enabled checkreqprot at runtime or via the kernel command line. We have yet to have anyone come to us and raise an objection to the deprecation or planned removal. It is worth noting that while this patch removes the checkreqprot functionality, it leaves the user visible interfaces (kernel command line and selinuxfs file) intact, just inert. This should help prevent breakages with existing userspace tools that correctly, but unnecessarily, disable checkreqprot at boot or runtime. Admins that attempt to enable checkreqprot will be met with a removal message in the kernel log. Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com> Signed-off-by: Paul Moore <paul@paul-moore.com>
27 lines
1.4 KiB
Plaintext
27 lines
1.4 KiB
Plaintext
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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REMOVAL UPDATE: The SELinux checkreqprot functionality was removed in
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March 2023, the original deprecation notice is shown below.
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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 no sooner than June 2021, 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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