rseq: Reject unknown flags on rseq unregister

It is preferrable to reject unknown flags within rseq unregistration
rather than to ignore them. It is an oversight caused by the fact that
the check for unknown flags is after the rseq unregister flag check.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191211161713.4490-2-mathieu.desnoyers@efficios.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/rseq.c b/kernel/rseq.c
index 27c48eb7de4025f94653c86878652ad57e660427..a4f86a9d6937cdfa2f13d1dcc9be863c1943d06f 100644 (file)
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -310,6 +310,8 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len,
        int ret;
 
        if (flags & RSEQ_FLAG_UNREGISTER) {
+               if (flags & ~RSEQ_FLAG_UNREGISTER)
+                       return -EINVAL;
                /* Unregister rseq for current thread. */
                if (current->rseq != rseq || !current->rseq)
                        return -EINVAL;