2023-06-01 09:57:45

by sunliming

Subject: [PATCH] tracing/user_events: Fix the incorrect trace record for null arguments events

The user_events support events that has null arguments. But the trace event
is discard and not really committed when the arguments is null, fix this
problem.

Signed-off-by: sunliming <[email protected]>
---
kernel/trace/trace_events_user.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index 0d91dac206ff..296bdfa674cb 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -1399,7 +1399,7 @@ static void user_event_ftrace(struct user_event *user, struct iov_iter *i,
if (unlikely(!entry))
return;

- if (unlikely(!copy_nofault(entry + 1, i->count, i)))
+ if (unlikely(i->count && !copy_nofault(entry + 1, i->count, i)))
goto discard;

if (!list_empty(&user->validators) &&
@@ -1440,7 +1440,7 @@ static void user_event_perf(struct user_event *user, struct iov_iter *i,

perf_fetch_caller_regs(regs);

- if (unlikely(!copy_nofault(perf_entry + 1, i->count, i)))
+ if (unlikely(i->count && !copy_nofault(perf_entry + 1, i->count, i)))
goto discard;

if (!list_empty(&user->validators) &&
--
2.25.1

2023-06-01 15:46:00

by Beau Belgrave

Subject: Re: [PATCH] tracing/user_events: Fix the incorrect trace record for null arguments events

On Thu, Jun 01, 2023 at 05:41:58PM +0800, sunliming wrote:
> The user_events support events that has null arguments. But the trace event
> is discard and not really committed when the arguments is null, fix this
> problem.
>

Thanks for the patch, this is a good catch! Can you reword this a bit?
"fix this problem" could be reworded to "Fix this by not attempting to
copy in non-zero data".

Would you mind adding this case to either the perf or ftrace self-test?
It's a really good edge case.

Thanks,
-Beau

> Signed-off-by: sunliming <[email protected]>
> ---
> kernel/trace/trace_events_user.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
> index 0d91dac206ff..296bdfa674cb 100644
> --- a/kernel/trace/trace_events_user.c
> +++ b/kernel/trace/trace_events_user.c
> @@ -1399,7 +1399,7 @@ static void user_event_ftrace(struct user_event *user, struct iov_iter *i,
> if (unlikely(!entry))
> return;
>
> - if (unlikely(!copy_nofault(entry + 1, i->count, i)))
> + if (unlikely(i->count && !copy_nofault(entry + 1, i->count, i)))
> goto discard;
>
> if (!list_empty(&user->validators) &&
> @@ -1440,7 +1440,7 @@ static void user_event_perf(struct user_event *user, struct iov_iter *i,
>
> perf_fetch_caller_regs(regs);
>
> - if (unlikely(!copy_nofault(perf_entry + 1, i->count, i)))
> + if (unlikely(i->count && !copy_nofault(perf_entry + 1, i->count, i)))
> goto discard;
>
> if (!list_empty(&user->validators) &&
> --
> 2.25.1