Commit 5f843ed4 authored Apr 15, 2019 by Masami Hiramatsu Committed by Ingo Molnar Apr 16, 2019

kprobes: Fix error check when reusing optimized probes



The following commit introduced a bug in one of our error paths:

  819319fc ("kprobes: Return error if we fail to reuse kprobe instead of BUG_ON()")

it missed to handle the return value of kprobe_optready() as
error-value. In reality, the kprobe_optready() returns a bool
result, so "true" case must be passed instead of 0.

This causes some errors on kprobe boot-time selftests on ARM:

 [   ] Beginning kprobe tests...
 [   ] Probe ARM code
 [   ]     kprobe
 [   ]     kretprobe
 [   ] ARM instruction simulation
 [   ]     Check decoding tables
 [   ]     Run test cases
 [   ] FAIL: test_case_handler not run
 [   ] FAIL: Test andge	r10, r11, r14, asr r7
 [   ] FAIL: Scenario 11
 ...
 [   ] FAIL: Scenario 7
 [   ] Total instruction simulation tests=1631, pass=1433 fail=198
 [   ] kprobe tests failed

This can happen if an optimized probe is unregistered and next
kprobe is registered on same address until the previous probe
is not reclaimed.

If this happens, a hidden aggregated probe may be kept in memory,
and no new kprobe can probe same address. Also, in that case
register_kprobe() will return "1" instead of minus error value,
which can mislead caller logic.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: David S . Miller <davem@davemloft.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Naveen N . Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org # v5.0+
Fixes: 819319fc ("kprobes: Return error if we fail to reuse kprobe instead of BUG_ON()")
Link: http://lkml.kernel.org/r/155530808559.32517.539898325433642204.stgit@devnote2


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 618d919c

kernel/kprobes.c

+2 −4

Original line number	Original line	Diff line number	Diff line
	@@ -709,7 +709,6 @@ static void unoptimize_kprobe(struct kprobe *p, bool force)
	static int reuse_unused_kprobe(struct kprobe *ap)		static int reuse_unused_kprobe(struct kprobe *ap)
	{		{
	struct optimized_kprobe *op;		struct optimized_kprobe *op;
	int ret;

	/*		/*
	* Unused kprobe MUST be on the way of delayed unoptimizing (means		* Unused kprobe MUST be on the way of delayed unoptimizing (means
	@@ -720,9 +719,8 @@ static int reuse_unused_kprobe(struct kprobe *ap)
	/* Enable the probe again */		/* Enable the probe again */
	ap->flags &= ~KPROBE_FLAG_DISABLED;		ap->flags &= ~KPROBE_FLAG_DISABLED;
	/* Optimize it again (remove from op->list) */		/* Optimize it again (remove from op->list) */
	ret = kprobe_optready(ap);		if (!kprobe_optready(ap))
	if (ret)		return -EINVAL;
	return ret;

	optimize_kprobe(ap);		optimize_kprobe(ap);
	return 0;		return 0;

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