Re: [PATCH v2] tracepoint: Do not fail unregistering a probe due to memory allocation
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2021-01-27 14:32:59
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On Wed, 27 Jan 2021 18:08:34 +1100 Alexey Kardashevskiy [off-list ref] wrote:
I am running syzkaller and the kernel keeps crashing in __traceiter_##_name. This patch makes these crashes happen lot less
I have another solution to the above issue. But I'm now concerned with what you write below.
quoted hunk ↗ jump to hunk
often (and so did the v1) but the kernel still crashes (examples below but the common thing is that they crash in tracepoints). Disasm points to __DO_TRACE_CALL(name) and this fixes it: ========================--- a/include/linux/tracepoint.h +++ b/include/linux/tracepoint.h@@ -313,6 +313,7 @@ static inline struct tracepoint*tracepoint_ptr_deref(tracepoint_ptr_t *p) \ it_func_ptr = \ rcu_dereference_raw((&__tracepoint_##_name)->funcs); \ + if (it_func_ptr) \
Looking at v2 of the patch, I found a bug that could make this happen. I'm looking at doing something else that doesn't affect the fast path nor does it bloat the kernel more than necessary. I'll see if I can get that patch out today. Thanks for the report. -- Steve