* The coding format is too messy, reformat to improve readability
and get closer to Linux kernel coding style.
* While at it, update .clang-format file to linux-mainline state.
* Following the advice that was given by member in rksu group, by replacing ALL to untrusted_app.
$ /system/bin/stat /proc/1
Result:
08-15 14:57:54.370 20062 20062 W stat : type=1400 audit(0.0:9564): avc: denied { getattr } for path="/proc/1" dev="proc" ino=12308 scontext=u:r:untrusted_app_27:s0:c27,c258,c512,c768 tcontext=u:r:init:s0 tclass=dir permissive=0 app=com.termux
(issue
438bd5fd6d (commitcomment-163785768))
Test: Checker pass.
* Any issue? Let me know.
Tested-by: rsuntk <rsuntk@yukiprjkt.my.id>
Signed-off-by: rsuntk <rsuntk@yukiprjkt.my.id>
* Maybe there's much better solution than this.
This reverts commit 438bd5fd6dac74ba63ef627124f0d2f552b1cb31.
Signed-off-by: rsuntk <rsuntk@yukiprjkt.my.id>
get_policydb() uses rcu_dereference() to read pointers to selinux_state.policy.
But in the SELinux implementation, these pointers are assigned once during
initialization and never changed with rcu_assign_pointer(), rendering the
rcu_dereference() call in get_policydb() completely useless. This just adds
unwanted overhead and implies concurrency pattern that is not even present in
the kernel.
Therefore, read the pointers directly since it's safe.
* selinux_state.ss needs more context.
Signed-off-by: Tashfin Shakeer Rhythm <tashfinshakeerrhythm@gmail.com>
Currently, handle_sepolicy() holds an RCU read lock across the entire
function including calls to strncpy_from_user() which can sleep, which
is illegal in RCU semantics.
This triggers the following warning when the kernel is compiled with
CONFIG_DEBUG_ATOMIC_SLEEP enabled:
[ 8.526345] BUG: sleeping function called from invalid context at lib/strncpy_from_user.c:40
[ 8.526349] in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 683, name: ksud
[ 8.526351] preempt_count: 0, expected: 0
[ 8.526352] RCU nest depth: 1, expected: 0
[ 8.526354] 1 lock held by ksud/683:
[ 8.526355] #0: ffffffe013e1b970 (rcu_read_lock){....}, at: handle_sepolicy+0xe4/0xaa0
[ 8.526365] CPU: 6 PID: 683 Comm: ksud Tainted: G W 5.4.289-Scarlet-v2.2-beta2 #1
[ 8.526366] Hardware name: redwood based Qualcomm Technologies, Inc. SM7325 (DT)
[ 8.526367] Call trace:
[ 8.526371] dump_backtrace+0x0/0x1c0
[ 8.526374] dump_stack+0x90/0xcc
[ 8.526376] __might_sleep+0x1a0/0x200
[ 8.526378] __might_fault+0x28/0x40
[ 8.526381] strncpy_from_user+0xac/0x300
[ 8.526383] handle_sepolicy+0x588/0xaa0
[ 8.526385] ksu_handle_prctl+0x368/0xd60
[ 8.526386] ksu_task_prctl+0xc/0x20
[ 8.526389] security_task_prctl+0x5c/0xa0
[ 8.526391] __arm64_sys_prctl+0x58/0x7e0
[ 8.526393] do_el0_svc+0x68/0x120
[ 8.526394] el0_sync_handler+0x11c/0x1c0
[ 8.526395] el0_sync+0x140/0x180
To fix this, replace the rcu_read_lock() with the `ksu_rules` mutex_lock()
introduced with commit 9014c663d1eb4 ("kernel: selinux: rules: Fix illegal RCU
lock usage in apply_kernelsu_rules()") which allows sleeping.
This mutex_lock() ensures mutual exclusion between threads invoking dynamic
policy modifications via handle_sepolicy() and those applying KernelSU rules
via apply_kernelsu_rules(), both of which access the policydb structure through
get_policydb().
Signed-off-by: Tashfin Shakeer Rhythm <tashfinshakeerrhythm@gmail.com>
* We got a splat related to atomic sleep.
* The trace is from strncpy_from_user and might_fault
Same case:
e47115e009
Signed-off-by: rsuntk <rsuntk@yukiprjkt.my.id>
When kernel is compiled with CONFIG_DEBUG_ATOMIC_SLEEP enabled, it prints
the following splat in dmesg during post boot:
[ 6.739169] init: Opening SELinux policy
[ 6.751520] init: Loading SELinux policy
[ 6.894684] SELinux: policy capability network_peer_controls=1
[ 6.894688] SELinux: policy capability open_perms=1
[ 6.894690] SELinux: policy capability extended_socket_class=1
[ 6.894691] SELinux: policy capability always_check_network=0
[ 6.894693] SELinux: policy capability cgroup_seclabel=0
[ 6.894695] SELinux: policy capability nnp_nosuid_transition=1
[ 7.214323] selinux: SELinux: Loaded file context from:
[ 7.214332] selinux: /system/etc/selinux/plat_file_contexts
[ 7.214339] selinux: /system_ext/etc/selinux/system_ext_file_contexts
[ 7.214345] selinux: /product/etc/selinux/product_file_contexts
[ 7.214350] selinux: /vendor/etc/selinux/vendor_file_contexts
[ 7.214356] selinux: /odm/etc/selinux/odm_file_contexts
[ 7.216398] KernelSU: /system/bin/init argc: 2
[ 7.216401] KernelSU: /system/bin/init first arg: second_stage
[ 7.216403] KernelSU: /system/bin/init second_stage executed
[ 7.216506] BUG: sleeping function called from invalid context at security/selinux/ss/hashtab.c:47
[ 7.216512] in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 1, name: init
[ 7.216516] preempt_count: 0, expected: 0
[ 7.216518] RCU nest depth: 1, expected: 0
[ 7.216524] CPU: 6 PID: 1 Comm: init Not tainted 5.4.289-Scarlet-v2.0-beta3 #1
[ 7.216526] Hardware name: redwood based Qualcomm Technologies, Inc. SM7325 (DT)
[ 7.216528] Call trace:
[ 7.216536] dump_backtrace+0x0/0x210
[ 7.216539] show_stack+0x14/0x20
[ 7.216544] dump_stack+0x9c/0xec
[ 7.216548] __might_resched+0x1f0/0x210
[ 7.216552] hashtab_insert+0x38/0x230
[ 7.216557] add_type+0xd4/0x2e0
[ 7.216559] ksu_type+0x24/0x60
[ 7.216562] apply_kernelsu_rules+0xa8/0x650
[ 7.216565] ksu_handle_execveat_ksud+0x2a8/0x460
[ 7.216568] ksu_handle_execveat+0x2c/0x60
[ 7.216571] __arm64_sys_execve+0xe8/0xf0
[ 7.216574] el0_svc_common+0xf4/0x1a0
[ 7.216577] do_el0_svc+0x2c/0x40
[ 7.216579] el0_sync_handler+0x18c/0x200
[ 7.216582] el0_sync+0x140/0x180
This is because apply_kernelsu_rules() uses rcu_read_lock() to protect
SELinux policy modifications. However, cond_resched() from
hashtab_insert() at security/selinux/ss/hashtab.c is internally called
and it sleeps which is illegal under an RCU read-side critical section.
While replacing it with a spinlock would suppress the warning, this is
fundamentally incorrect because sleeping is illegal while holding a
spinlock and spinlock would turn off preemption which isn't an ideal
solution since it intentionally turns off rescheduling, and can lead
to deadlocks.
Instead, replace the RCU lock with a mutex lock. Mutex lock allows
sleeping when necessary, which is appropriate here because
apply_kernelsu_rules() runs in process context, not in atomic or
interrupt context. As apply_kernelsu_rules() is invoked only once during
post boot (SYSTEM_RUNNING), the mutex lock does not introduce any major
runtime performance regression and provides correct synchronization.
Fixes: tiann#2637
Signed-off-by: Tashfin Shakeer Rhythm <tashfinshakeerrhythm@gmail.com>
This checks `selinux_state` and `current_sid` supports in a raw way.
Feels more reliable than the version checks.
Supersedes #401, fixes#280, fixes#400.
4.9's last release aka 4.9.337 still needs the same fallbacks as 4.9.212
and breaks otherwise, upgrade this to fix compilation
Tested and working on POCO F1, 4.9.337
_selinux_state_ is backported to 4.9 kernel with the 4.9.212 release,
use it to fix the build.
many thanks to @reallysnow for figuring this out.
inspired by
d7c2c5f02a
