tracepoint: Fix race between tracing and removing tracepoint

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/[email protected]

Cc: [email protected]
Fixes: d25e37d89dd2f ("tracepoint: Optimize using static_call()")
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Alexey Kardashevskiy <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>

0 files changed, 0 insertions, 0 deletions