• Dave Jones's avatar
    selinux: conditionally reschedule in mls_convert_context while loading selinux policy · 9a591f39
    Dave Jones authored
    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: default avatarDave Jones <davej@redhat.com>
    Acked-by: default avatarStephen Smalley <sds@tycho.nsa.gov>
    Signed-off-by: default avatarPaul Moore <pmoore@redhat.com>
    9a591f39
mls.c 15.7 KB