linux-kernel - [patch 3/5] lib/vdso/32: Provide legacy syscall fallbacks

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Message-Id: <20190728131648.786513965@linutronix.de>
Date:   Sun, 28 Jul 2019 15:12:54 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Andy Lutomirski <luto@...nel.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Kees Cook <keescook@...omium.org>,
        Paul Bolle <pebolle@...cali.nl>, Will Deacon <will@...nel.org>
Subject: [patch 3/5] lib/vdso/32: Provide legacy syscall fallbacks

To address the regression which causes seccomp to deny applications the
access to clock_gettime64() and clock_getres64() syscalls because they
are not enabled in the existing filters.

That trips over the fact that 32bit VDSOs use the new clock_gettime64() and
clock_getres64() syscalls in the fallback path.

Implement a __cvdso_clock_get*time32() variants which invokes the legacy
32bit syscalls when the architecture requests it.

The conditional can go away once all architectures are converted.

Fixes: 00b26474c2f1 ("lib/vdso: Provide generic VDSO implementation")
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 lib/vdso/gettimeofday.c |   46 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 45 insertions(+), 1 deletion(-)

--- a/lib/vdso/gettimeofday.c
+++ b/lib/vdso/gettimeofday.c
@@ -117,6 +117,8 @@ static __maybe_unused int
 	return 0;
 }
 
+#ifndef VDSO_HAS_32BIT_FALLBACK
+
 static __maybe_unused int
 __cvdso_clock_gettime32(clockid_t clock, struct old_timespec32 *res)
 {
@@ -132,10 +134,29 @@ static __maybe_unused int
 		res->tv_sec = ts.tv_sec;
 		res->tv_nsec = ts.tv_nsec;
 	}
-
 	return ret;
 }
 
+#else
+
+static __maybe_unused int
+__cvdso_clock_gettime32(clockid_t clock, struct old_timespec32 *res)
+{
+	struct __kernel_timespec ts;
+	int ret;
+
+	ret = __cvdso_clock_gettime_common(clock, &ts);
+
+	if (likely(!ret)) {
+		res->tv_sec = ts.tv_sec;
+		res->tv_nsec = ts.tv_nsec;
+		return 0;
+	}
+	return clock_gettime32_fallback(clock, res);
+}
+
+#endif
+
 static __maybe_unused int
 __cvdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
 {
@@ -225,6 +246,8 @@ int __cvdso_clock_getres(clockid_t clock
 	return 0;
 }
 
+#ifndef VDSO_HAS_32BIT_FALLBACK
+
 static __maybe_unused int
 __cvdso_clock_getres_time32(clockid_t clock, struct old_timespec32 *res)
 {
@@ -241,4 +264,25 @@ static __maybe_unused int
 	}
 	return ret;
 }
+
+#else
+
+static __maybe_unused int
+__cvdso_clock_getres_time32(clockid_t clock, struct old_timespec32 *res)
+{
+	struct __kernel_timespec ts;
+	int ret;
+
+	ret = __cvdso_clock_getres_common(clock, &ts);
+
+	if (likely(!ret)) {
+		res->tv_sec = ts.tv_sec;
+		res->tv_nsec = ts.tv_nsec;
+		return 0;
+	}
+
+	return clock_getres32_fallback(clock, res);
+}
+#endif
+
 #endif /* VDSO_HAS_CLOCK_GETRES */