Commit 448dca8c authored by Mathieu Desnoyers's avatar Mathieu Desnoyers Committed by Peter Zijlstra
Browse files

rseq: Use pr_warn_once() when deprecated/unknown ABI flags are encountered 



These commits use WARN_ON_ONCE() and kill the offending processes when
deprecated and unknown flags are encountered:

commit c17a6ff9 ("rseq: Kill process when unknown flags are encountered in ABI structures")
commit 0190e419 ("rseq: Deprecate RSEQ_CS_FLAG_NO_RESTART_ON_* flags")

The WARN_ON_ONCE() triggered by userspace input prevents use of
Syzkaller to fuzz the rseq system call.

Replace this WARN_ON_ONCE() by pr_warn_once() messages which contain
actually useful information.

Reported-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Link: https://lkml.kernel.org/r/20221102130635.7379-1-mathieu.desnoyers@efficios.com
parent 094226ad

kernel/rseq.c

+17 −2
Original line number Diff line number Diff line
@@ -171,12 +171,27 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs) 
	return 0;

}



static bool rseq_warn_flags(const char *str, u32 flags)

{

	u32 test_flags;



	if (!flags)

		return false;

	test_flags = flags & RSEQ_CS_NO_RESTART_FLAGS;

	if (test_flags)

		pr_warn_once("Deprecated flags (%u) in %s ABI structure", test_flags, str);

	test_flags = flags & ~RSEQ_CS_NO_RESTART_FLAGS;

	if (test_flags)

		pr_warn_once("Unknown flags (%u) in %s ABI structure", test_flags, str);

	return true;

}



static int rseq_need_restart(struct task_struct *t, u32 cs_flags)

{

	u32 flags, event_mask;

	int ret;



	if (WARN_ON_ONCE(cs_flags & RSEQ_CS_NO_RESTART_FLAGS) || cs_flags)

	if (rseq_warn_flags("rseq_cs", cs_flags))

		return -EINVAL;



	/* Get thread flags. */
@@ -184,7 +199,7 @@ static int rseq_need_restart(struct task_struct *t, u32 cs_flags) 
	if (ret)

		return ret;



	if (WARN_ON_ONCE(flags & RSEQ_CS_NO_RESTART_FLAGS) || flags)

	if (rseq_warn_flags("rseq", flags))

		return -EINVAL;



	/*