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Subject[PATCH v2 0/9] kprobes: Fix and improve blacklist symbols
Date
Hi,

Here is the v2 series of kprobes blacklist bugfix and improvements mainly
on x86 (since I started testing on qemu-x86).

>From v1, I just removed stable-ml from Cc (but tagged [1/9]) and added
Steve's Ack.

This has been started from discussion about KPROBE_ENENTS_ON_NOTRACE
configuration. I tried to find notrace functions which can cause kernel
crash with kprobes using following script.

====
#!/bin/sh

i=0;
cat notrace_functions | while read f ; do
if echo p:event$i $f >> /sys/kernel/debug/tracing/kprobe_events; then
echo "Probing on $f"
echo 1 > /sys/kernel/debug/tracing/events/kprobes/event$i/enable
fi
i=$((i+1))
done
====

And I found several functions which must be blacklisted.
- optprobe template code, which is just a template code and
never be executed. Moreover, since it can be copied and
reused, if we probe it, it modifies the template code and
can cause a crash. ([1/9][2/9])
- functions which is called before kprobe_int3_handler()
handles kprobes. This can cause a breakpoint recursion. ([3/9])
- IRQ entry text, which should not be probed since register/pagetable
status has not been stable at that point. ([4/9])
- Suffixed symbols, like .constprop, .part etc. Those suffixed
symbols never be blacklisted even if the non-suffixed version
has been blacklisted. ([5/9])
- hardirq tracer also works before int3 handling. ([6/9])
- preempt_check debug function also is involved in int3 handling.
([7/9])
- RCU debug routine is also called before kprobe_int3_handler().
([8/9])
- Some lockdep functions are also involved in int3 handling.
([9/9])

Of course there still may be some functions which can be called
by configuration change, I'll continue to test it.

Thank you,

---

Masami Hiramatsu (9):
x86/kprobes: Prohibit probing on optprobe template code
x86/kprobes: Move trampoline code into RODATA
x86/kprobes: Prohibit probing on functions before kprobe_int3_handler()
x86/kprobes: Prohibit probing on IRQ handlers directly
kprobes: Search non-suffixed symbol in blacklist
kprobes: Prohibit probing on hardirq tracers
kprobes: Prohibit probing on preempt_check debug functions
kprobes: Prohibit probing on RCU debug routine
kprobes: Prohibit probing on lockdep functions


arch/x86/kernel/alternative.c | 3 ++-
arch/x86/kernel/ftrace.c | 3 ++-
arch/x86/kernel/kprobes/core.c | 7 +++++++
arch/x86/kernel/kprobes/opt.c | 4 ++--
arch/x86/kernel/traps.c | 1 +
kernel/kprobes.c | 21 ++++++++++++++++++++-
kernel/locking/lockdep.c | 7 ++++++-
kernel/rcu/tree.c | 2 ++
kernel/rcu/update.c | 2 ++
kernel/trace/trace_irqsoff.c | 9 +++++++--
kernel/trace/trace_preemptirq.c | 5 +++++
lib/smp_processor_id.c | 7 +++++--
12 files changed, 61 insertions(+), 10 deletions(-)

--
Masami Hiramatsu (Linaro) <mhiramat@kernel.org>

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