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612c353178
linux/security/selinux/ss
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Dave Jones 612c353178 selinux: conditionally reschedule in mls_convert_context while loading selinux policy 
On a slow machine (with debugging enabled), upgrading selinux policy may take
a considerable amount of time. Long enough that the softlockup detector
gets triggered.

The backtrace looks like this..

 > BUG: soft lockup - CPU#2 stuck for 23s! [load_policy:19045]
 > Call Trace:
 >  [<ffffffff81221ddf>] symcmp+0xf/0x20
 >  [<ffffffff81221c27>] hashtab_search+0x47/0x80
 >  [<ffffffff8122e96c>] mls_convert_context+0xdc/0x1c0
 >  [<ffffffff812294e8>] convert_context+0x378/0x460
 >  [<ffffffff81229170>] ? security_context_to_sid_core+0x240/0x240
 >  [<ffffffff812221b5>] sidtab_map+0x45/0x80
 >  [<ffffffff8122bb9f>] security_load_policy+0x3ff/0x580
 >  [<ffffffff810788a8>] ? sched_clock_cpu+0xa8/0x100
 >  [<ffffffff810786dd>] ? sched_clock_local+0x1d/0x80
 >  [<ffffffff810788a8>] ? sched_clock_cpu+0xa8/0x100
 >  [<ffffffff8103096a>] ? __change_page_attr_set_clr+0x82a/0xa50
 >  [<ffffffff810786dd>] ? sched_clock_local+0x1d/0x80
 >  [<ffffffff810788a8>] ? sched_clock_cpu+0xa8/0x100
 >  [<ffffffff8103096a>] ? __change_page_attr_set_clr+0x82a/0xa50
 >  [<ffffffff810788a8>] ? sched_clock_cpu+0xa8/0x100
 >  [<ffffffff81534ddc>] ? retint_restore_args+0xe/0xe
 >  [<ffffffff8109c82d>] ? trace_hardirqs_on_caller+0xfd/0x1c0
 >  [<ffffffff81279a2e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
 >  [<ffffffff810d28a8>] ? rcu_irq_exit+0x68/0xb0
 >  [<ffffffff81534ddc>] ? retint_restore_args+0xe/0xe
 >  [<ffffffff8121e947>] sel_write_load+0xa7/0x770
 >  [<ffffffff81139633>] ? vfs_write+0x1c3/0x200
 >  [<ffffffff81210e8e>] ? security_file_permission+0x1e/0xa0
 >  [<ffffffff8113952b>] vfs_write+0xbb/0x200
 >  [<ffffffff811581c7>] ? fget_light+0x397/0x4b0
 >  [<ffffffff81139c27>] SyS_write+0x47/0xa0
 >  [<ffffffff8153bde4>] tracesys+0xdd/0xe2

Stephen Smalley suggested:

 > Maybe put a cond_resched() within the ebitmap_for_each_positive_bit()
 > loop in mls_convert_context()?

That seems to do the trick. Tested by downgrading and re-upgrading selinux-policy-targeted.

Signed-off-by: Dave Jones <davej@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <pmoore@redhat.com>
2014-05-15 17:06:14 -04:00
..
avtab.c SELinux: allow userspace to read policy back out of the kernel 2010-10-21 10:12:58 +11:00
avtab.h SELinux: Use dentry name in new object labeling 2011-02-01 11:12:30 -05:00
conditional.c selinux: Casting (void *) value returned by kmalloc is useless 2011-12-19 11:23:56 +11:00
conditional.h selinux: sparse fix: fix several warnings in the security server code 2011-09-09 16:56:32 -07:00
constraint.h SELinux: Update policy version to support constraints info 2013-11-19 17:34:23 -05:00
context.h SELinux: allow default source/target selectors for user/role/range 2012-04-09 12:22:47 -04:00
ebitmap.c SELinux: Reduce overhead of mls_level_isvalid() function call 2013-07-25 13:02:18 -04:00
ebitmap.h SELinux: Increase ebitmap_node size for 64-bit configuration 2013-07-25 13:02:31 -04:00
hashtab.c
hashtab.h
mls_types.h SELinux: Reduce overhead of mls_level_isvalid() function call 2013-07-25 13:02:18 -04:00
mls.c selinux: conditionally reschedule in mls_convert_context while loading selinux policy 2014-05-15 17:06:14 -04:00
mls.h doc: Update the email address for Paul Moore in various source files 2011-08-01 17:58:33 -07:00
policydb.c SELinux: bigendian problems with filename trans rules 2014-02-20 12:07:58 -05:00
policydb.h SELinux: Update policy version to support constraints info 2013-11-19 17:34:23 -05:00
services.c selinux: add gfp argument to security_xfrm_policy_alloc and fix callers 2014-03-10 08:30:02 +01:00
services.h
sidtab.c selinux: cache sidtab_context_to_sid results 2010-12-07 16:44:01 -05:00
sidtab.h selinux: cache sidtab_context_to_sid results 2010-12-07 16:44:01 -05:00
status.c selinux: fix up style problem on /selinux/status 2010-10-21 10:12:41 +11:00
symtab.c
symtab.h