bug: sleep in atomic context

[Alban Browaeys]

mutex_lock in app_new_null_profile called by:
  profile_transition
    apparmor_bprm_set_creds
is with preempt disabled thus in atomic context. This as it is in between get_buffers and put_buffers in apparmor_bprm_set_creds.

I am dubious about switching to spinlock to fix this issue. The aim of commit 4227c333f65cddc6c2 which switched this code to get_buffers was to limit failure and improve performance.

Cheers
Alban

nov. 14 14:09:09 cyclope audit[7152]: AVC apparmor="ALLOWED" operation="exec" profile="/usr/sbin/sssd" name="/usr/sbin/adcli" pid=7152 comm="sssd_be" requested_mask="x" denied_mask="x" fsuid=0 ouid=0 target="/usr/sbin/sssd//null-/usr/sbin/adcli"
nov. 14 14:09:09 cyclope kernel: BUG: sleeping function called from invalid context at kernel/locking/mutex.c:747
nov. 14 14:09:09 cyclope kernel: in_atomic(): 1, irqs_disabled(): 0, pid: 7152, name: sssd_be
nov. 14 14:09:09 cyclope kernel: 1 lock held by sssd_be/7152:
nov. 14 14:09:09 cyclope kernel: #0: (&sig->cred_guard_mutex){....}, at: [<ffffffff8182d53e>] prepare_bprm_creds+0x4e/0x100
nov. 14 14:09:09 cyclope kernel: CPU: 3 PID: 7152 Comm: sssd_be Not tainted 4.14.0prahal+intel #150
nov. 14 14:09:09 cyclope kernel: Hardware name: LENOVO 20CDCTO1WW/20CDCTO1WW, BIOS GQET53WW (1.33 ) 09/15/2017
nov. 14 14:09:09 cyclope kernel: Call Trace:
nov. 14 14:09:09 cyclope kernel: dump_stack+0xb0/0x135
nov. 14 14:09:09 cyclope kernel: ? _atomic_dec_and_lock+0x15b/0x15b
nov. 14 14:09:09 cyclope kernel: ? lockdep_print_held_locks+0xc4/0x130
nov. 14 14:09:09 cyclope kernel: ___might_sleep+0x29c/0x320
nov. 14 14:09:09 cyclope kernel: ? rq_clock+0xf0/0xf0
nov. 14 14:09:09 cyclope kernel: ? __kernel_text_address+0xd/0x40
nov. 14 14:09:09 cyclope kernel: __might_sleep+0x95/0x190
nov. 14 14:09:09 cyclope kernel: ? aa_new_null_profile+0x50a/0x960
nov. 14 14:09:09 cyclope kernel: __mutex_lock+0x13e/0x1a20
nov. 14 14:09:09 cyclope kernel: ? aa_new_null_profile+0x50a/0x960
nov. 14 14:09:09 cyclope kernel: ? save_stack+0x43/0xd0
nov. 14 14:09:09 cyclope kernel: ? kmem_cache_alloc_trace+0x13f/0x290
nov. 14 14:09:09 cyclope kernel: ? mutex_lock_io_nested+0x1880/0x1880
nov. 14 14:09:09 cyclope kernel: ? profile_transition+0x932/0x2d40
nov. 14 14:09:09 cyclope kernel: ? apparmor_bprm_set_creds+0x1479/0x1f70
nov. 14 14:09:09 cyclope kernel: ? security_bprm_set_creds+0x5a/0x80
nov. 14 14:09:09 cyclope kernel: ? prepare_binprm+0x366/0x980
nov. 14 14:09:09 cyclope kernel: ? do_execveat_common.isra.30+0x12a9/0x2350
nov. 14 14:09:09 cyclope kernel: ? SyS_execve+0x2c/0x40
nov. 14 14:09:09 cyclope kernel: ? do_syscall_64+0x228/0x650
nov. 14 14:09:09 cyclope kernel: ? entry_SYSCALL64_slow_path+0x25/0x25
nov. 14 14:09:09 cyclope kernel: ? deactivate_slab.isra.62+0x49d/0x5e0
nov. 14 14:09:09 cyclope kernel: ? save_stack_trace+0x16/0x20
nov. 14 14:09:09 cyclope kernel: ? init_object+0x88/0x90
nov. 14 14:09:09 cyclope kernel: ? ___slab_alloc+0x520/0x590
nov. 14 14:09:09 cyclope kernel: ? ___slab_alloc+0x520/0x590
nov. 14 14:09:09 cyclope kernel: ? aa_alloc_proxy+0xab/0x200
nov. 14 14:09:09 cyclope kernel: ? lock_downgrade+0x7e0/0x7e0
nov. 14 14:09:09 cyclope kernel: ? memcg_kmem_get_cache+0x970/0x970
nov. 14 14:09:09 cyclope kernel: ? kasan_unpoison_shadow+0x35/0x50
nov. 14 14:09:09 cyclope kernel: ? kasan_unpoison_shadow+0x35/0x50
nov. 14 14:09:09 cyclope kernel: ? kasan_kmalloc+0xad/0xe0
nov. 14 14:09:09 cyclope kernel: ? aa_alloc_proxy+0xab/0x200
nov. 14 14:09:09 cyclope kernel: ? kmem_cache_alloc_trace+0x13f/0x290
nov. 14 14:09:09 cyclope kernel: ? aa_alloc_proxy+0xab/0x200
nov. 14 14:09:09 cyclope kernel: ? aa_alloc_proxy+0xab/0x200
nov. 14 14:09:09 cyclope kernel: ? _raw_spin_unlock+0x22/0x30
nov. 14 14:09:09 cyclope kernel: ? vec_find+0xa0/0xa0
nov. 14 14:09:09 cyclope kernel: ? aa_label_init+0x6f/0x230
nov. 14 14:09:09 cyclope kernel: ? __label_insert+0x3e0/0x3e0
nov. 14 14:09:09 cyclope kernel: ? kmem_cache_alloc_trace+0x13f/0x290
nov. 14 14:09:09 cyclope kernel: ? aa_alloc_profile+0x58/0x200
nov. 14 14:09:09 cyclope kernel: mutex_lock_nested+0x16/0x20
nov. 14 14:09:09 cyclope kernel: ? mutex_lock_nested+0x16/0x20
nov. 14 14:09:09 cyclope kernel: aa_new_null_profile+0x50a/0x960
nov. 14 14:09:09 cyclope kernel: ? aa_fqlookupn_profile+0xdc0/0xdc0
nov. 14 14:09:09 cyclope kernel: ? aa_compute_fperms+0x4b5/0x640
nov. 14 14:09:09 cyclope kernel: ? disconnect.isra.2+0x1b0/0x1b0
nov. 14 14:09:09 cyclope kernel: ? aa_str_perms+0x8d/0xe0
nov. 14 14:09:09 cyclope kernel: profile_transition+0x932/0x2d40
nov. 14 14:09:09 cyclope kernel: ? up_read+0x1a/0x40
nov. 14 14:09:09 cyclope kernel: ? ext4_xattr_get+0x15c/0xaf0 [ext4]
nov. 14 14:09:09 cyclope kernel: ? x_table_lookup+0x190/0x190
nov. 14 14:09:09 cyclope kernel: ? ext4_xattr_ibody_get+0x590/0x590 [ext4]
nov. 14 14:09:09 cyclope kernel: ? sched_clock+0x9/0x10
nov. 14 14:09:09 cyclope kernel: ? sched_clock+0x9/0x10
nov. 14 14:09:09 cyclope kernel: ? ext4_xattr_security_get+0x1a/0x20 [ext4]
nov. 14 14:09:09 cyclope kernel: ? __vfs_getxattr+0x6d/0xa0
nov. 14 14:09:09 cyclope kernel: ? get_vfs_caps_from_disk+0x114/0x720
nov. 14 14:09:09 cyclope kernel: ? sched_clock+0x9/0x10
nov. 14 14:09:09 cyclope kernel: ? sched_clock+0x9/0x10
nov. 14 14:09:09 cyclope kernel: ? tsc_resume+0x10/0x10
nov. 14 14:09:09 cyclope kernel: ? get_vfs_caps_from_disk+0x720/0x720
nov. 14 14:09:09 cyclope kernel: ? native_sched_clock_from_tsc+0x201/0x2b0
nov. 14 14:09:09 cyclope kernel: ? sched_clock+0x9/0x10
nov. 14 14:09:09 cyclope kernel: ? sched_clock_cpu+0x1b/0x170
nov. 14 14:09:09 cyclope kernel: ? find_held_lock+0x3c/0x1e0
nov. 14 14:09:09 cyclope kernel: ? rb_insert_color_cached+0x1660/0x1660
nov. 14 14:09:09 cyclope kernel: apparmor_bprm_set_creds+0x1479/0x1f70
nov. 14 14:09:09 cyclope kernel: ? sched_clock+0x9/0x10
nov. 14 14:09:09 cyclope kernel: ? handle_onexec+0x31d0/0x31d0
nov. 14 14:09:09 cyclope kernel: ? tsc_resume+0x10/0x10
nov. 14 14:09:09 cyclope kernel: ? graph_lock+0xd0/0xd0
nov. 14 14:09:09 cyclope kernel: ? tsc_resume+0x10/0x10
nov. 14 14:09:09 cyclope kernel: ? sched_clock_cpu+0x1b/0x170
nov. 14 14:09:09 cyclope kernel: ? sched_clock+0x9/0x10
nov. 14 14:09:09 cyclope kernel: ? sched_clock+0x9/0x10
nov. 14 14:09:09 cyclope kernel: ? sched_clock_cpu+0x1b/0x170
nov. 14 14:09:09 cyclope kernel: ? find_held_lock+0x3c/0x1e0
nov. 14 14:09:09 cyclope kernel: security_bprm_set_creds+0x5a/0x80
nov. 14 14:09:09 cyclope kernel: prepare_binprm+0x366/0x980
nov. 14 14:09:09 cyclope kernel: ? install_exec_creds+0x150/0x150
nov. 14 14:09:09 cyclope kernel: ? __might_fault+0x89/0xb0
nov. 14 14:09:09 cyclope kernel: ? up_read+0x40/0x40
nov. 14 14:09:09 cyclope kernel: ? get_user_arg_ptr.isra.18+0x2c/0x70
nov. 14 14:09:09 cyclope kernel: ? count.isra.20.constprop.32+0x7c/0xf0
nov. 14 14:09:09 cyclope kernel: do_execveat_common.isra.30+0x12a9/0x2350
nov. 14 14:09:09 cyclope kernel: ? prepare_bprm_creds+0x100/0x100
nov. 14 14:09:09 cyclope kernel: ? _raw_spin_unlock+0x22/0x30
nov. 14 14:09:09 cyclope kernel: ? deactivate_slab.isra.62+0x49d/0x5e0
nov. 14 14:09:09 cyclope kernel: ? save_stack_trace+0x16/0x20
nov. 14 14:09:09 cyclope kernel: ? init_object+0x88/0x90
nov. 14 14:09:09 cyclope kernel: ? ___slab_alloc+0x520/0x590
nov. 14 14:09:09 cyclope kernel: ? ___slab_alloc+0x520/0x590
nov. 14 14:09:09 cyclope kernel: ? kasan_check_write+0x14/0x20
nov. 14 14:09:09 cyclope kernel: ? memcg_kmem_get_cache+0x970/0x970
nov. 14 14:09:09 cyclope kernel: ? kasan_unpoison_shadow+0x35/0x50
nov. 14 14:09:09 cyclope kernel: ? glob_match+0x730/0x730
nov. 14 14:09:09 cyclope kernel: ? kmem_cache_alloc+0x225/0x280
nov. 14 14:09:09 cyclope kernel: ? getname_flags+0xb8/0x510
nov. 14 14:09:09 cyclope kernel: ? mm_fault_error+0x2e0/0x2e0
nov. 14 14:09:09 cyclope kernel: ? getname_flags+0xf6/0x510
nov. 14 14:09:09 cyclope kernel: ? ptregs_sys_vfork+0x10/0x10
nov. 14 14:09:09 cyclope kernel: SyS_execve+0x2c/0x40
nov. 14 14:09:09 cyclope kernel: do_syscall_64+0x228/0x650
nov. 14 14:09:09 cyclope kernel: ? syscall_return_slowpath+0x2f0/0x2f0
nov. 14 14:09:09 cyclope kernel: ? syscall_return_slowpath+0x167/0x2f0
nov. 14 14:09:09 cyclope kernel: ? prepare_exit_to_usermode+0x220/0x220
nov. 14 14:09:09 cyclope kernel: ? prepare_exit_to_usermode+0xda/0x220
nov. 14 14:09:09 cyclope kernel: ? perf_trace_sys_enter+0x1060/0x1060
nov. 14 14:09:09 cyclope kernel: ? __put_user_4+0x1c/0x30
nov. 14 14:09:09 cyclope kernel: entry_SYSCALL64_slow_path+0x25/0x25
nov. 14 14:09:09 cyclope kernel: RIP: 0033:0x7f9320f23637
nov. 14 14:09:09 cyclope kernel: RSP: 002b:00007fff783be338 EFLAGS: 00000202 ORIG_RAX: 000000000000003b
nov. 14 14:09:09 cyclope kernel: RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f9320f23637
nov. 14 14:09:09 cyclope kernel: RDX: 0000558c35002a70 RSI: 0000558c3505bd10 RDI: 0000558c35018b90
nov. 14 14:09:09 cyclope kernel: RBP: 0000558c34b63ae8 R08: 0000558c3505bd10 R09: 0000000000000080
nov. 14 14:09:09 cyclope kernel: R10: 0000000000000095 R11: 0000000000000202 R12: 0000000000000001
nov. 14 14:09:09 cyclope kernel: R13: 0000558c35018b90 R14: 0000558c3505bd18 R15: 0000558c3505bd10

[Seth Arnold (seth-arnold)]

Hi Alban, nice find, thanks for reporting this bug to us.