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tracepoint: Fix race between tracing and removing tracepoint

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commit c8b186a8d54d7e12d28e9f9686cb00ff18fc2ab2 upstream.

When executing a tracepoint, the tracepoint's func is dereferenced twice -
in __DO_TRACE() (where the returned pointer is checked) and later on in
__traceiter_##_name where the returned pointer is dereferenced without
checking which leads to races against tracepoint_removal_sync() and
crashes.

This adds a check before referencing the pointer in tracepoint_ptr_deref.

Link: https://lkml.kernel.org/r/20210202072326.120557-1-aik@ozlabs.ru

Cc: stable@vger.kernel.org
Fixes: d25e37d89d ("tracepoint: Optimize using static_call()")
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alexey Kardashevskiy 2021-02-02 18:23:26 +11:00 committed by Greg Kroah-Hartman
parent 9e4a668f4f
commit 059e68da31
1 changed files with 7 additions and 5 deletions
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12
include/linux/tracepoint.h
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@ -307,11 +307,13 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
\
it_func_ptr = \
rcu_dereference_raw((&__tracepoint_##_name)->funcs); \
do { \
it_func = (it_func_ptr)->func; \
__data = (it_func_ptr)->data; \
((void(*)(void *, proto))(it_func))(__data, args); \
} while ((++it_func_ptr)->func); \
if (it_func_ptr) { \
do { \
it_func = (it_func_ptr)->func; \
__data = (it_func_ptr)->data; \
((void(*)(void *, proto))(it_func))(__data, args); \
} while ((++it_func_ptr)->func); \
} \
return 0; \
} \
DEFINE_STATIC_CALL(tp_func_##_name, __traceiter_##_name);