Re: [PATCH] uprobes: prevent mutex_lock() under rcu_read_lock()
On Mon, 20 May 2024 22:30:17 -0700
Andrii Nakryiko wrote:
> Recent changes made uprobe_cpu_buffer preparation lazy, and moved it
> deeper into __uprobe_trace_func(). This is problematic because
> __uprobe_trace_func() is called inside rcu_read_lock()/rcu_read_unlock()
> block, which then calls prepare_uprobe_buffer() -> uprobe_buffer_get() ->
> mutex_lock(>mutex), leading to a splat about using mutex under
> non-sleepable RCU:
>
> BUG: sleeping function called from invalid context at
> kernel/locking/mutex.c:585
>in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 98231, name:
> stress-ng-sigq
>preempt_count: 0, expected: 0
>RCU nest depth: 1, expected: 0
>...
>Call Trace:
>
> dump_stack_lvl+0x3d/0xe0
> __might_resched+0x24c/0x270
> ? prepare_uprobe_buffer+0xd5/0x1d0
> __mutex_lock+0x41/0x820
> ? ___perf_sw_event+0x206/0x290
> ? __perf_event_task_sched_in+0x54/0x660
> ? __perf_event_task_sched_in+0x54/0x660
> prepare_uprobe_buffer+0xd5/0x1d0
> __uprobe_trace_func+0x4a/0x140
> uprobe_dispatcher+0x135/0x280
> ? uprobe_dispatcher+0x94/0x280
> uprobe_notify_resume+0x650/0xec0
> ? atomic_notifier_call_chain+0x21/0x110
> ? atomic_notifier_call_chain+0xf8/0x110
> irqentry_exit_to_user_mode+0xe2/0x1e0
> asm_exc_int3+0x35/0x40
>RIP: 0033:0x7f7e1d4da390
>Code: 33 04 00 0f 1f 80 00 00 00 00 f3 0f 1e fa b9 01 00 00 00 e9 b2 fc ff
> ff 66 90 f3 0f 1e fa 31 c9 e9 a5 fc ff ff 0f 1f 44 00 00 0f 1e fa b8 27
> 00 00 00 0f 05 c3 0f 1f 40 00 f3 0f 1e fa b8 6e
>RSP: 002b:7ffd2abc3608 EFLAGS: 0246
>RAX: RBX: 76d325f1 RCX:
>RDX: 76d325f1 RSI: 000a RDI: 7ffd2abc3690
>RBP: 000a R08: 00017fb7 R09: 00017fb7
>R10: 00017fb7 R11: 0246 R12: 00017ff2
>R13: 7ffd2abc3610 R14: R15: 7ffd2abc3780
>
>
> Luckily, it's easy to fix by moving prepare_uprobe_buffer() to be called
> slightly earlier: into uprobe_trace_func() and uretprobe_trace_func(), outside
> of RCU locked section. This still keeps this buffer preparation lazy and helps
> avoid the overhead when it's not needed. E.g., if there is only BPF uprobe
> handler installed on a given uprobe, buffer won't be initialized.
>
> Note, the other user of prepare_uprobe_buffer(), __uprobe_perf_func(), is not
> affected, as it doesn't prepare buffer under RCU read lock.
>
Oops, good catch! This looks good to me. Let me pick it.
Let me add a simple uprobe test in ftracetest so that this error can
detect in selftests. (I could reproduced it.)
Thank you,
> Fixes: 1b8f85defbc8 ("uprobes: prepare uprobe args buffer lazily")
> Reported-by: Breno Leitao
> Signed-off-by: Andrii Nakryiko
> ---
> kernel/trace/trace_uprobe.c | 14 +-
> 1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> index 8541fa1494ae..c98e3b3386ba 100644
> --- a/kernel/trace/trace_uprobe.c
> +++ b/kernel/trace/trace_uprobe.c
> @@ -970,19 +970,17 @@ static struct uprobe_cpu_buffer
> *prepare_uprobe_buffer(struct trace_uprobe *tu,
>
> static void __uprobe_trace_func(struct trace_uprobe *tu,
> unsigned long func, struct pt_regs *regs,
> - struct uprobe_cpu_buffer **ucbp,
> + struct uprobe_cpu_buffer *ucb,
> struct trace_event_file *trace_file)
> {
> struct uprobe_trace_entry_head *entry;
> struct trace_event_buffer fbuffer;
> - struct uprobe_cpu_buffer *ucb;
> void *data;
> int size, esize;
> struct trace_event_call *call = trace_probe_event_call(>tp);
>
> WARN_ON(call != trace_file->event_call);
>
> - ucb = prepare_uprobe_buffer(tu, regs, ucbp);
> if (WARN_ON_ONCE(ucb->dsize > PAGE_SIZE))
> return;
>
> @@ -1014,13 +1012,16 @@ static int uprobe_trace_func(struct trace_uprobe *tu,
> struct pt_regs *regs,
>struct uprobe_cpu_buffer **ucbp)
> {
> struct event_file_link *link;
> + struct uprobe_cpu_buffer *ucb;
>
> if (is_ret_probe(tu))
> return 0;
>
> + ucb = prepare_uprobe_buffer(tu, regs, ucbp);
> +
> rcu_read_lock();
> trace_probe_for_each_link_rcu(link, >tp)
> - __uprobe_trace_func(tu, 0, regs, ucbp, link->file);
> + __uprobe_trace_func(tu, 0, regs, ucb, link->file);
> rcu_read_unlock();
>
> return 0;
> @@ -1031,10 +1032,13 @@ static void uretprobe_trace_func(struct trace_uprobe
> *tu, unsigned long func,
>struct uprobe_cpu_buffer **ucbp)
> {
> struct event_file_link *link;
> + struct uprobe_cpu_buffer *ucb;
> +
> + ucb = prepare_uprobe_buffer(tu, regs, ucbp);
>
> rcu_read_lock();
>
Re: [PATCH] uprobes: prevent mutex_lock() under rcu_read_lock()
On Mon, May 20, 2024 at 10:30:17PM -0700, Andrii Nakryiko wrote:
> Recent changes made uprobe_cpu_buffer preparation lazy, and moved it
> deeper into __uprobe_trace_func(). This is problematic because
> __uprobe_trace_func() is called inside rcu_read_lock()/rcu_read_unlock()
> block, which then calls prepare_uprobe_buffer() -> uprobe_buffer_get() ->
> mutex_lock(>mutex), leading to a splat about using mutex under
> non-sleepable RCU:
>
> BUG: sleeping function called from invalid context at
> kernel/locking/mutex.c:585
>in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 98231, name:
> stress-ng-sigq
>preempt_count: 0, expected: 0
>RCU nest depth: 1, expected: 0
>...
>Call Trace:
>
> dump_stack_lvl+0x3d/0xe0
> __might_resched+0x24c/0x270
> ? prepare_uprobe_buffer+0xd5/0x1d0
> __mutex_lock+0x41/0x820
> ? ___perf_sw_event+0x206/0x290
> ? __perf_event_task_sched_in+0x54/0x660
> ? __perf_event_task_sched_in+0x54/0x660
> prepare_uprobe_buffer+0xd5/0x1d0
> __uprobe_trace_func+0x4a/0x140
> uprobe_dispatcher+0x135/0x280
> ? uprobe_dispatcher+0x94/0x280
> uprobe_notify_resume+0x650/0xec0
> ? atomic_notifier_call_chain+0x21/0x110
> ? atomic_notifier_call_chain+0xf8/0x110
> irqentry_exit_to_user_mode+0xe2/0x1e0
> asm_exc_int3+0x35/0x40
>RIP: 0033:0x7f7e1d4da390
>Code: 33 04 00 0f 1f 80 00 00 00 00 f3 0f 1e fa b9 01 00 00 00 e9 b2 fc ff
> ff 66 90 f3 0f 1e fa 31 c9 e9 a5 fc ff ff 0f 1f 44 00 00 0f 1e fa b8 27
> 00 00 00 0f 05 c3 0f 1f 40 00 f3 0f 1e fa b8 6e
>RSP: 002b:7ffd2abc3608 EFLAGS: 0246
>RAX: RBX: 76d325f1 RCX:
>RDX: 76d325f1 RSI: 000a RDI: 7ffd2abc3690
>RBP: 000a R08: 00017fb7 R09: 00017fb7
>R10: 00017fb7 R11: 0246 R12: 00017ff2
>R13: 7ffd2abc3610 R14: R15: 7ffd2abc3780
>
>
> Luckily, it's easy to fix by moving prepare_uprobe_buffer() to be called
> slightly earlier: into uprobe_trace_func() and uretprobe_trace_func(), outside
> of RCU locked section. This still keeps this buffer preparation lazy and helps
> avoid the overhead when it's not needed. E.g., if there is only BPF uprobe
> handler installed on a given uprobe, buffer won't be initialized.
>
> Note, the other user of prepare_uprobe_buffer(), __uprobe_perf_func(), is not
> affected, as it doesn't prepare buffer under RCU read lock.
>
> Fixes: 1b8f85defbc8 ("uprobes: prepare uprobe args buffer lazily")
> Reported-by: Breno Leitao
> Signed-off-by: Andrii Nakryiko
Tested-by: Breno Leitao
Re: [PATCH] uprobes: prevent mutex_lock() under rcu_read_lock()
On 05/20, Andrii Nakryiko wrote:
>
> Fixes: 1b8f85defbc8 ("uprobes: prepare uprobe args buffer lazily")
> Reported-by: Breno Leitao
> Signed-off-by: Andrii Nakryiko
> ---
> kernel/trace/trace_uprobe.c | 14 +-
> 1 file changed, 9 insertions(+), 5 deletions(-)
Reviewed-by: Oleg Nesterov
[PATCH] uprobes: prevent mutex_lock() under rcu_read_lock()
Recent changes made uprobe_cpu_buffer preparation lazy, and moved it
deeper into __uprobe_trace_func(). This is problematic because
__uprobe_trace_func() is called inside rcu_read_lock()/rcu_read_unlock()
block, which then calls prepare_uprobe_buffer() -> uprobe_buffer_get() ->
mutex_lock(>mutex), leading to a splat about using mutex under
non-sleepable RCU:
BUG: sleeping function called from invalid context at
kernel/locking/mutex.c:585
in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 98231, name:
stress-ng-sigq
preempt_count: 0, expected: 0
RCU nest depth: 1, expected: 0
...
Call Trace:
dump_stack_lvl+0x3d/0xe0
__might_resched+0x24c/0x270
? prepare_uprobe_buffer+0xd5/0x1d0
__mutex_lock+0x41/0x820
? ___perf_sw_event+0x206/0x290
? __perf_event_task_sched_in+0x54/0x660
? __perf_event_task_sched_in+0x54/0x660
prepare_uprobe_buffer+0xd5/0x1d0
__uprobe_trace_func+0x4a/0x140
uprobe_dispatcher+0x135/0x280
? uprobe_dispatcher+0x94/0x280
uprobe_notify_resume+0x650/0xec0
? atomic_notifier_call_chain+0x21/0x110
? atomic_notifier_call_chain+0xf8/0x110
irqentry_exit_to_user_mode+0xe2/0x1e0
asm_exc_int3+0x35/0x40
RIP: 0033:0x7f7e1d4da390
Code: 33 04 00 0f 1f 80 00 00 00 00 f3 0f 1e fa b9 01 00 00 00 e9 b2 fc ff
ff 66 90 f3 0f 1e fa 31 c9 e9 a5 fc ff ff 0f 1f 44 00 00 0f 1e fa b8 27 00
00 00 0f 05 c3 0f 1f 40 00 f3 0f 1e fa b8 6e
RSP: 002b:7ffd2abc3608 EFLAGS: 0246
RAX: RBX: 76d325f1 RCX:
RDX: 76d325f1 RSI: 000a RDI: 7ffd2abc3690
RBP: 000a R08: 00017fb7 R09: 00017fb7
R10: 00017fb7 R11: 0246 R12: 00017ff2
R13: 7ffd2abc3610 R14: R15: 7ffd2abc3780
Luckily, it's easy to fix by moving prepare_uprobe_buffer() to be called
slightly earlier: into uprobe_trace_func() and uretprobe_trace_func(), outside
of RCU locked section. This still keeps this buffer preparation lazy and helps
avoid the overhead when it's not needed. E.g., if there is only BPF uprobe
handler installed on a given uprobe, buffer won't be initialized.
Note, the other user of prepare_uprobe_buffer(), __uprobe_perf_func(), is not
affected, as it doesn't prepare buffer under RCU read lock.
Fixes: 1b8f85defbc8 ("uprobes: prepare uprobe args buffer lazily")
Reported-by: Breno Leitao
Signed-off-by: Andrii Nakryiko
---
kernel/trace/trace_uprobe.c | 14 +-
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 8541fa1494ae..c98e3b3386ba 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -970,19 +970,17 @@ static struct uprobe_cpu_buffer
*prepare_uprobe_buffer(struct trace_uprobe *tu,
static void __uprobe_trace_func(struct trace_uprobe *tu,
unsigned long func, struct pt_regs *regs,
- struct uprobe_cpu_buffer **ucbp,
+ struct uprobe_cpu_buffer *ucb,
struct trace_event_file *trace_file)
{
struct uprobe_trace_entry_head *entry;
struct trace_event_buffer fbuffer;
- struct uprobe_cpu_buffer *ucb;
void *data;
int size, esize;
struct trace_event_call *call = trace_probe_event_call(>tp);
WARN_ON(call != trace_file->event_call);
- ucb = prepare_uprobe_buffer(tu, regs, ucbp);
if (WARN_ON_ONCE(ucb->dsize > PAGE_SIZE))
return;
@@ -1014,13 +1012,16 @@ static int uprobe_trace_func(struct trace_uprobe *tu,
struct pt_regs *regs,
struct uprobe_cpu_buffer **ucbp)
{
struct event_file_link *link;
+ struct uprobe_cpu_buffer *ucb;
if (is_ret_probe(tu))
return 0;
+ ucb = prepare_uprobe_buffer(tu, regs, ucbp);
+
rcu_read_lock();
trace_probe_for_each_link_rcu(link, >tp)
- __uprobe_trace_func(tu, 0, regs, ucbp, link->file);
+ __uprobe_trace_func(tu, 0, regs, ucb, link->file);
rcu_read_unlock();
return 0;
@@ -1031,10 +1032,13 @@ static void uretprobe_trace_func(struct trace_uprobe
*tu, unsigned long func,
struct uprobe_cpu_buffer **ucbp)
{
struct event_file_link *link;
+ struct uprobe_cpu_buffer *ucb;
+
+ ucb = prepare_uprobe_buffer(tu, regs, ucbp);
rcu_read_lock();
trace_probe_for_each_link_rcu(link, >tp)
- __uprobe_trace_func(tu, func, regs, ucbp, link->file);
+ __uprobe_trace_func(tu, func, regs, ucb, link->file);
rcu_read_unlock();
}
--
2.43.0
