Messages in this thread Patch in this message | | | From | Cheng Jui Wang <> | Subject | [PATCH] lockdep: Zap lock classes with debug_locks == false again | Date | Tue, 15 Mar 2022 19:25:21 +0800 |
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If a lock_class_key has been registered but lockdep_unregister_key() is called with debug_locks == false. The lockdep_unregister_key() will not unregister the key and just return without error. Users may assume lockdep_unregister_key() always succeed and free the lock_class_key even if it is still remained in lockdep structures.
Which lead to following crash when 'cat /proc/lockdep' after debug_locks == false:
================================================================== BUG: KASAN: invalid-access in string+0x50/0x10c Read at addr f2ffff81ac61c880 by ... Pointer tag: [f2], memory tag: [fb] ... Call trace: dump_backtrace.cfi_jt+0x0/0x8 show_stack+0x1c/0x2c dump_stack_lvl+0xd8/0x16c print_address_description+0x90/0x2e8 __kasan_report+0x144/0x224 kasan_report+0x50/0xa0 __do_kernel_fault+0xf4/0x2a8 do_bad_area+0x34/0xf8 do_tag_check_fault+0x24/0x38 do_mem_abort+0x68/0x168 el1_abort+0x4c/0x74 el1_sync_handler+0x4c/0x8c el1_sync+0x8c/0x140 string+0x50/0x10c vsnprintf+0x468/0x69c seq_printf+0x8c/0xd8 print_name+0x64/0xf4 l_show+0x1a8/0x278 seq_read_iter+0x3cc/0x5fc proc_reg_read_iter+0xdc/0x1d4 vfs_read+0x2e0/0x354 ksys_read+0x7c/0xec __arm64_sys_read+0x20/0x30 el0_svc_common.llvm.8008154191216078041+0xd8/0x20c do_el0_svc+0x28/0xa0 el0_svc+0x24/0x38 el0_sync_handler+0x88/0xec el0_sync+0x1b4/0x1c0
... ==================================================================
Allow lockdep_unregister_key to zap lock classes with debug_locks == false again. Remove the WARN_ON_ONCE(!found) and only zap lock classes when the key can be found.
Fixes: 8b39adbee805 ("locking/lockdep: Make lockdep_unregister_key() honor 'debug_locks' again") Signed-off-by: Cheng Jui Wang <cheng-jui.wang@mediatek.com> --- kernel/locking/lockdep.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index f8a0212189ca..90dadecb2577 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -6305,8 +6305,7 @@ void lockdep_unregister_key(struct lock_class_key *key) return; raw_local_irq_save(flags); - if (!graph_lock()) - goto out_irq; + lockdep_lock(); pf = get_pending_free(); hlist_for_each_entry_rcu(k, hash_head, hash_entry) { @@ -6316,11 +6315,11 @@ void lockdep_unregister_key(struct lock_class_key *key) break; } } - WARN_ON_ONCE(!found); - __lockdep_free_key_range(pf, key, 1); - call_rcu_zapped(pf); - graph_unlock(); -out_irq: + if (found) { + __lockdep_free_key_range(pf, key, 1); + call_rcu_zapped(pf); + } + lockdep_unlock(); raw_local_irq_restore(flags); /* Wait until is_dynamic_key() has finished accessing k->hash_entry. */ -- 2.18.0
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