diff options
| author | Song Liu <song@kernel.org> | 2022-09-26 17:41:46 -0700 |
|---|---|---|
| committer | Steven Rostedt (Google) <rostedt@goodmis.org> | 2022-09-27 14:48:27 -0400 |
| commit | 9d2ce78ddcee159eb6a97449e9c68b6d60b9cec4 (patch) | |
| tree | d70dad241dd143c0a4b5a4a58a63753d86de8bb7 /kernel/trace/ftrace.c | |
| parent | 0ce0638edf5ec83343302b884fa208179580700a (diff) | |
ftrace: Fix recursive locking direct_mutex in ftrace_modify_direct_caller
Naveen reported recursive locking of direct_mutex with sample
ftrace-direct-modify.ko:
[ 74.762406] WARNING: possible recursive locking detected
[ 74.762887] 6.0.0-rc6+ #33 Not tainted
[ 74.763216] --------------------------------------------
[ 74.763672] event-sample-fn/1084 is trying to acquire lock:
[ 74.764152] ffffffff86c9d6b0 (direct_mutex){+.+.}-{3:3}, at: \
register_ftrace_function+0x1f/0x180
[ 74.764922]
[ 74.764922] but task is already holding lock:
[ 74.765421] ffffffff86c9d6b0 (direct_mutex){+.+.}-{3:3}, at: \
modify_ftrace_direct+0x34/0x1f0
[ 74.766142]
[ 74.766142] other info that might help us debug this:
[ 74.766701] Possible unsafe locking scenario:
[ 74.766701]
[ 74.767216] CPU0
[ 74.767437] ----
[ 74.767656] lock(direct_mutex);
[ 74.767952] lock(direct_mutex);
[ 74.768245]
[ 74.768245] *** DEADLOCK ***
[ 74.768245]
[ 74.768750] May be due to missing lock nesting notation
[ 74.768750]
[ 74.769332] 1 lock held by event-sample-fn/1084:
[ 74.769731] #0: ffffffff86c9d6b0 (direct_mutex){+.+.}-{3:3}, at: \
modify_ftrace_direct+0x34/0x1f0
[ 74.770496]
[ 74.770496] stack backtrace:
[ 74.770884] CPU: 4 PID: 1084 Comm: event-sample-fn Not tainted ...
[ 74.771498] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), ...
[ 74.772474] Call Trace:
[ 74.772696] <TASK>
[ 74.772896] dump_stack_lvl+0x44/0x5b
[ 74.773223] __lock_acquire.cold.74+0xac/0x2b7
[ 74.773616] lock_acquire+0xd2/0x310
[ 74.773936] ? register_ftrace_function+0x1f/0x180
[ 74.774357] ? lock_is_held_type+0xd8/0x130
[ 74.774744] ? my_tramp2+0x11/0x11 [ftrace_direct_modify]
[ 74.775213] __mutex_lock+0x99/0x1010
[ 74.775536] ? register_ftrace_function+0x1f/0x180
[ 74.775954] ? slab_free_freelist_hook.isra.43+0x115/0x160
[ 74.776424] ? ftrace_set_hash+0x195/0x220
[ 74.776779] ? register_ftrace_function+0x1f/0x180
[ 74.777194] ? kfree+0x3e1/0x440
[ 74.777482] ? my_tramp2+0x11/0x11 [ftrace_direct_modify]
[ 74.777941] ? __schedule+0xb40/0xb40
[ 74.778258] ? register_ftrace_function+0x1f/0x180
[ 74.778672] ? my_tramp1+0xf/0xf [ftrace_direct_modify]
[ 74.779128] register_ftrace_function+0x1f/0x180
[ 74.779527] ? ftrace_set_filter_ip+0x33/0x70
[ 74.779910] ? __schedule+0xb40/0xb40
[ 74.780231] ? my_tramp1+0xf/0xf [ftrace_direct_modify]
[ 74.780678] ? my_tramp2+0x11/0x11 [ftrace_direct_modify]
[ 74.781147] ftrace_modify_direct_caller+0x5b/0x90
[ 74.781563] ? 0xffffffffa0201000
[ 74.781859] ? my_tramp1+0xf/0xf [ftrace_direct_modify]
[ 74.782309] modify_ftrace_direct+0x1b2/0x1f0
[ 74.782690] ? __schedule+0xb40/0xb40
[ 74.783014] ? simple_thread+0x2a/0xb0 [ftrace_direct_modify]
[ 74.783508] ? __schedule+0xb40/0xb40
[ 74.783832] ? my_tramp2+0x11/0x11 [ftrace_direct_modify]
[ 74.784294] simple_thread+0x76/0xb0 [ftrace_direct_modify]
[ 74.784766] kthread+0xf5/0x120
[ 74.785052] ? kthread_complete_and_exit+0x20/0x20
[ 74.785464] ret_from_fork+0x22/0x30
[ 74.785781] </TASK>
Fix this by using register_ftrace_function_nolock in
ftrace_modify_direct_caller.
Link: https://lkml.kernel.org/r/20220927004146.1215303-1-song@kernel.org
Fixes: 53cd885bc5c3 ("ftrace: Allow IPMODIFY and DIRECT ops on the same function")
Reported-and-tested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace/ftrace.c')
| -rw-r--r-- | kernel/trace/ftrace.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 5a1ec7e1af33..406d0597c409 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5427,6 +5427,8 @@ static struct ftrace_ops stub_ops = { * it is safe to modify the ftrace record, where it should be * currently calling @old_addr directly, to call @new_addr. * + * This is called with direct_mutex locked. + * * Safety checks should be made to make sure that the code at * @rec->ip is currently calling @old_addr. And this must * also update entry->direct to @new_addr. @@ -5439,6 +5441,8 @@ int __weak ftrace_modify_direct_caller(struct ftrace_func_entry *entry, unsigned long ip = rec->ip; int ret; + lockdep_assert_held(&direct_mutex); + /* * The ftrace_lock was used to determine if the record * had more than one registered user to it. If it did, @@ -5461,7 +5465,7 @@ int __weak ftrace_modify_direct_caller(struct ftrace_func_entry *entry, if (ret) goto out_lock; - ret = register_ftrace_function(&stub_ops); + ret = register_ftrace_function_nolock(&stub_ops); if (ret) { ftrace_set_filter_ip(&stub_ops, ip, 1, 0); goto out_lock; |