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cfff75d897
linux/security
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Ondrej Mosnacek cfff75d897 selinux: reorder hooks to make runtime disable less broken 
Commit b1d9e6b064 ("LSM: Switch to lists of hooks") switched the LSM
infrastructure to use per-hook lists, which meant that removing the
hooks for a given module was no longer atomic. Even though the commit
clearly documents that modules implementing runtime revmoval of hooks
(only SELinux attempts this madness) need to take special precautions to
avoid race conditions, SELinux has never addressed this.

By inserting an artificial delay between the loop iterations of
security_delete_hooks() (I used 100 ms), booting to a state where
SELinux is enabled, but policy is not yet loaded, and running these
commands:

    while true; do ping -c 1 <some IP>; done &
    echo -n 1 >/sys/fs/selinux/disable
    kill %1
    wait

...I was able to trigger NULL pointer dereferences in various places. I
also have a report of someone getting panics on a stock RHEL-8 kernel
after setting SELINUX=disabled in /etc/selinux/config and rebooting
(without adding "selinux=0" to kernel command-line).

Reordering the SELinux hooks such that those that allocate structures
are removed last seems to prevent these panics. It is very much possible
that this doesn't make the runtime disable completely race-free, but at
least it makes the operation much less fragile.

Cc: stable@vger.kernel.org
Fixes: b1d9e6b064 ("LSM: Switch to lists of hooks")
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Reviewed-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
2020-01-10 15:26:55 -05:00
..
apparmor + Features 2019-12-03 12:51:35 -08:00
integrity x86/efi: remove unused variables 2019-11-29 22:23:46 +11:00
keys KEYS: trusted: Remove set but not used variable 'keyhndl' 2019-11-12 21:45:37 +02:00
loadpin proc/sysctl: add shared variables for range check 2019-07-18 17:08:07 -07:00
lockdown security,lockdown,selinux: implement SELinux lockdown 2019-12-09 17:53:58 -05:00
safesetid security/safesetid: Replace rcu_swap_protected() with rcu_replace_pointer() 2019-10-30 08:45:57 -07:00
selinux selinux: reorder hooks to make runtime disable less broken 2020-01-10 15:26:55 -05:00
smack pipe: Reduce #inclusion of pipe_fs_i.h 2019-10-23 17:02:34 +01:00
tomoyo treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
yama proc/sysctl: add shared variables for range check 2019-07-18 17:08:07 -07:00
commoncap.c Merge branch 'next-lsm' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2019-07-09 12:24:21 -07:00
device_cgroup.c device_cgroup: Export devcgroup_check_permission 2019-10-07 15:11:38 -05:00
inode.c Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
Kconfig Merge branch 'next-lockdown' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2019-09-28 08:14:15 -07:00
Kconfig.hardening meminit fix 2019-07-28 12:33:15 -07:00
lsm_audit.c security,lockdown,selinux: implement SELinux lockdown 2019-12-09 17:53:58 -05:00
Makefile security: only build lsm_audit if CONFIG_SECURITY=y 2019-12-10 13:51:42 -05:00
min_addr.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
security.c security,lockdown,selinux: implement SELinux lockdown 2019-12-09 17:53:58 -05:00