Make seccomp-bpf sandbox work on Linux/X32

Allow clock_gettime syscall with X32 bit masked off. Apparently
this is required for at least some kernel versions. bz#2142
Patch mostly by Colin Watson. ok dtucker@

1 files changed, 9 insertions, 1 deletions

diff --git a/sandbox-seccomp-filter.c b/sandbox-seccomp-filter.c
index 14006b99a..3a1aedce7 100644
--- a/sandbox-seccomp-filter.c
+++ b/sandbox-seccomp-filter.c
@@ -228,7 +228,15 @@ static const struct sock_filter preauth_insns[] = {
         SC_ALLOW_ARG(__NR_ioctl, 1, Z90STAT_STATUS_MASK),
         SC_ALLOW_ARG(__NR_ioctl, 1, ICARSAMODEXPO),
         SC_ALLOW_ARG(__NR_ioctl, 1, ICARSACRT),
-#endif /* defined(__NR_ioctl) && defined(__s390__) */
+#endif
+#if defined(__x86_64__) && defined(__ILP32__) && defined(__X32_SYSCALL_BIT)
+        /*
+         * On Linux x32, the clock_gettime VDSO falls back to the
+         * x86-64 syscall under some circumstances, e.g.
+         * https://bugs.debian.org/849923
+         */
+        SC_ALLOW(__NR_clock_gettime & ~__X32_SYSCALL_BIT);
+#endif
 
         /* Default deny */
         BPF_STMT(BPF_RET+BPF_K, SECCOMP_FILTER_FAIL),