diff mbox series

[RFC,v2,13/18] oslib-posix: Ignore fcntl("/dev/null", F_SETFL, O_NONBLOCK) failure

Message ID 20190129175403.18017-14-philmd@redhat.com
State New
Headers show
Series OpenBSD: Enable qtesting | expand

Commit Message

Philippe Mathieu-Daudé Jan. 29, 2019, 5:53 p.m. UTC 
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."

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 util/oslib-posix.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

Comments

Peter Maydell Feb. 5, 2019, 1:22 p.m. UTC | #1 
On Tue, 29 Jan 2019 at 17:59, Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
>
> 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."
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  util/oslib-posix.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/util/oslib-posix.c b/util/oslib-posix.c
> index 4ce1ba9ca4..2f0f27e6d9 100644
> --- a/util/oslib-posix.c
> +++ b/util/oslib-posix.c
> @@ -244,7 +244,17 @@ 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.
> +         */
> +        assert(errno == ENODEV);
> +    }
> +#else
>      assert(f != -1);
> +#endif

You might also add "It's OK if we fail to set O_NONBLOCK on devices
like /dev/null, because they will never block anyway."

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM
Philippe Mathieu-Daudé Feb. 5, 2019, 1:43 p.m. UTC | #2 
On 2/5/19 2:22 PM, Peter Maydell wrote:
> On Tue, 29 Jan 2019 at 17:59, Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
>>
>> 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."
>>
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>> ---
>>  util/oslib-posix.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/util/oslib-posix.c b/util/oslib-posix.c
>> index 4ce1ba9ca4..2f0f27e6d9 100644
>> --- a/util/oslib-posix.c
>> +++ b/util/oslib-posix.c
>> @@ -244,7 +244,17 @@ 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.
>> +         */
>> +        assert(errno == ENODEV);
>> +    }
>> +#else
>>      assert(f != -1);
>> +#endif
> 
> You might also add "It's OK if we fail to set O_NONBLOCK on devices
> like /dev/null, because they will never block anyway."

OK!

> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

Thanks for reviewing this series :)

> 
> thanks
> -- PMM
>
Michael S. Tsirkin Feb. 5, 2019, 5:40 p.m. UTC | #3 
On Tue, Jan 29, 2019 at 06:53:58PM +0100, Philippe Mathieu-Daudé wrote:
> 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."
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

> ---
>  util/oslib-posix.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/util/oslib-posix.c b/util/oslib-posix.c
> index 4ce1ba9ca4..2f0f27e6d9 100644
> --- a/util/oslib-posix.c
> +++ b/util/oslib-posix.c
> @@ -244,7 +244,17 @@ 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.
> +         */
> +        assert(errno == ENODEV);
> +    }
> +#else
>      assert(f != -1);
> +#endif
>  }
>  
>  int socket_set_fast_reuse(int fd)
> -- 
> 2.20.1
diff mbox series

Patch

diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 4ce1ba9ca4..2f0f27e6d9 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -244,7 +244,17 @@  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.
+         */
+        assert(errno == ENODEV);
+    }
+#else
     assert(f != -1);
+#endif
 }
 
 int socket_set_fast_reuse(int fd)