oslib-posix: Ignore fcntl("/dev/null", F_SETFL, O_NONBLOCK) failure
Previous to OpenBSD 6.3 [1], fcntl(F_SETFL) is not permitted on
memory devices.
Trying this call sets errno to ENODEV ("not a memory device"):
19 ENODEV Operation not supported by device.
An attempt was made to apply an inappropriate function to a device,
for example, trying to read a write-only device such as a printer.
Do not assert fcntl failures in this specific case (errno set to ENODEV)
on OpenBSD. This fixes:
$ lm32-softmmu/qemu-system-lm32
assertion "f != -1" failed: file "util/oslib-posix.c", line 247, function "qemu_set_nonblock"
Abort trap (core dumped)
[1] The fix seems https://github.com/openbsd/src/commit/c2a35b387f9d3c
"fcntl(F_SETFL) invokes the FIONBIO and FIOASYNC ioctls internally, so
the memory devices (/dev/null, /dev/zero, etc) need to permit them."
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20190307142822.8531-2-philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 37c5854..326d92d 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -244,7 +244,19 @@
f = fcntl(fd, F_GETFL);
assert(f != -1);
f = fcntl(fd, F_SETFL, f | O_NONBLOCK);
+#ifdef __OpenBSD__
+ if (f == -1) {
+ /*
+ * Previous to OpenBSD 6.3, fcntl(F_SETFL) is not permitted on
+ * memory devices and sets errno to ENODEV.
+ * It's OK if we fail to set O_NONBLOCK on devices like /dev/null,
+ * because they will never block anyway.
+ */
+ assert(errno == ENODEV);
+ }
+#else
assert(f != -1);
+#endif
}
int socket_set_fast_reuse(int fd)
