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[Qemu-devel] [PATCH v3 1/2] oslib-posix: Ignore fcntl("/dev/null", F_SET
From: |
Philippe Mathieu-Daudé |
Subject: |
[Qemu-devel] [PATCH v3 1/2] oslib-posix: Ignore fcntl("/dev/null", F_SETFL, O_NONBLOCK) failure |
Date: |
Thu, 7 Mar 2019 15:28:21 +0100 |
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 <address@hidden>
Reviewed-by: Michael S. Tsirkin <address@hidden>
Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
---
util/oslib-posix.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 37c5854b9c..326d92dcd2 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -244,7 +244,19 @@ void qemu_set_nonblock(int fd)
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)
--
2.20.1