999765145e
This replaces the reverse table lookup and reverse cache with a
hashtable which improves cache-miss reverse-lookup times from
O(n) to O(1)* and maintains the same performance as a reverse
cache hit.
This reduces the time needed to add a new sidtab entry from ~500us
to 5us on a Pixel 3 when there are ~10,000 sidtab entries.
The implementation uses the kernel's generic hashtable API,
It uses the context's string represtation as the hash source,
and the kernels generic string hashing algorithm full_name_hash()
to reduce the string to a 32 bit value.
This change also maintains the improvement introduced in
commit ee1a84fdfeed ("selinux: overhaul sidtab to fix bug and improve
performance") which removed the need to keep the current sidtab
locked during policy reload. It does however introduce periodic
locking of the target sidtab while converting the hashtable. Sidtab
entries are never modified or removed, so the context struct stored
in the sid_to_context tree can also be used for the context_to_sid
hashtable to reduce memory usage.
This bug was reported by:
- On the selinux bug tracker.
BUG: kernel softlockup due to too many SIDs/contexts #37
https://github.com/SELinuxProject/selinux-kernel/issues/37
- Jovana Knezevic on Android's bugtracker.
Bug: 140252993
"During multi-user performance testing, we create and remove users
many times. selinux_android_restorecon_pkgdir goes from 1ms to over
20ms after about 200 user creations and removals. Accumulated over
~280 packages, that adds a significant time to user creation,
making perf benchmarks unreliable."
* Hashtable lookup is only O(1) when n < the number of buckets.
Signed-off-by: Jeff Vander Stoep <jeffv@google.com>
Reported-by: Stephen Smalley <sds@tycho.nsa.gov>
Reported-by: Jovana Knezevic <jovanak@google.com>
Reviewed-by: Stephen Smalley <sds@tycho.nsa.gov>
Tested-by: Stephen Smalley <sds@tycho.nsa.gov>
[PM: subj tweak, removed changelog from patch description]
Signed-off-by: Paul Moore <paul@paul-moore.com>
(cherry picked from commit 66f8e2f03c02e812002f8e9e465681cc62edda5b)
Bug: 140252993
Change-Id: Iead2a1d90731ae24fefec2a40af5ffdc457ac916
Signed-off-by: Jeff Vander Stoep <jeffv@google.com>
113 lines
4.4 KiB
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113 lines
4.4 KiB
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config SECURITY_SELINUX
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bool "NSA SELinux Support"
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depends on SECURITY_NETWORK && AUDIT && NET && INET
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select NETWORK_SECMARK
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default n
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help
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This selects NSA Security-Enhanced Linux (SELinux).
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You will also need a policy configuration and a labeled filesystem.
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If you are unsure how to answer this question, answer N.
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config SECURITY_SELINUX_BOOTPARAM
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bool "NSA SELinux boot parameter"
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depends on SECURITY_SELINUX
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default n
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help
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This option adds a kernel parameter 'selinux', which allows SELinux
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to be disabled at boot. If this option is selected, SELinux
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functionality can be disabled with selinux=0 on the kernel
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command line. The purpose of this option is to allow a single
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kernel image to be distributed with SELinux built in, but not
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necessarily enabled.
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If you are unsure how to answer this question, answer N.
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config SECURITY_SELINUX_BOOTPARAM_VALUE
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int "NSA SELinux boot parameter default value"
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depends on SECURITY_SELINUX_BOOTPARAM
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range 0 1
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default 1
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help
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This option sets the default value for the kernel parameter
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'selinux', which allows SELinux to be disabled at boot. If this
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option is set to 0 (zero), the SELinux kernel parameter will
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default to 0, disabling SELinux at bootup. If this option is
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set to 1 (one), the SELinux kernel parameter will default to 1,
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enabling SELinux at bootup.
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If you are unsure how to answer this question, answer 1.
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config SECURITY_SELINUX_DISABLE
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bool "NSA SELinux runtime disable"
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depends on SECURITY_SELINUX
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select SECURITY_WRITABLE_HOOKS
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default n
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help
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This option enables writing to a selinuxfs node 'disable', which
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allows SELinux to be disabled at runtime prior to the policy load.
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SELinux will then remain disabled until the next boot.
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This option is similar to the selinux=0 boot parameter, but is to
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support runtime disabling of SELinux, e.g. from /sbin/init, for
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portability across platforms where boot parameters are difficult
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to employ.
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NOTE: selecting this option will disable the '__ro_after_init'
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kernel hardening feature for security hooks. Please consider
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using the selinux=0 boot parameter instead of enabling this
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option.
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If you are unsure how to answer this question, answer N.
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config SECURITY_SELINUX_DEVELOP
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bool "NSA SELinux Development Support"
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depends on SECURITY_SELINUX
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default y
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help
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This enables the development support option of NSA SELinux,
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which is useful for experimenting with SELinux and developing
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policies. If unsure, say Y. With this option enabled, the
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kernel will start in permissive mode (log everything, deny nothing)
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unless you specify enforcing=1 on the kernel command line. You
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can interactively toggle the kernel between enforcing mode and
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permissive mode (if permitted by the policy) via /selinux/enforce.
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config SECURITY_SELINUX_AVC_STATS
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bool "NSA SELinux AVC Statistics"
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depends on SECURITY_SELINUX
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default y
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help
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This option collects access vector cache statistics to
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/selinux/avc/cache_stats, which may be monitored via
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tools such as avcstat.
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config SECURITY_SELINUX_CHECKREQPROT_VALUE
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int "NSA SELinux checkreqprot default value"
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depends on SECURITY_SELINUX
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range 0 1
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default 0
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help
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This option sets the default value for the 'checkreqprot' flag
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that determines whether SELinux checks the protection requested
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by the application or the protection that will be applied by the
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kernel (including any implied execute for read-implies-exec) for
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mmap and mprotect calls. If this option is set to 0 (zero),
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SELinux will default to checking the protection that will be applied
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by the kernel. If this option is set to 1 (one), SELinux will
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default to checking the protection requested by the application.
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The checkreqprot flag may be changed from the default via the
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'checkreqprot=' boot parameter. It may also be changed at runtime
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via /selinux/checkreqprot if authorized by policy.
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If you are unsure how to answer this question, answer 0.
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config SECURITY_SELINUX_SIDTAB_HASH_BITS
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int "NSA SELinux sidtab hashtable size"
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depends on SECURITY_SELINUX
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range 8 13
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default 9
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help
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This option sets the number of buckets used in the sidtab hashtable
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to 2^SECURITY_SELINUX_SIDTAB_HASH_BITS buckets. The number of hash
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collisions may be viewed at /sys/fs/selinux/ss/sidtab_hash_stats. If
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chain lengths are high (e.g. > 20) then selecting a higher value here
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will ensure that lookups times are short and stable.
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