* [Qemu-devel] [PATCH v2] qemu-sockets: do not test path with access() before unlinking
@ 2015-11-04 13:48 Paolo Bonzini
2015-11-04 14:08 ` Markus Armbruster
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Paolo Bonzini @ 2015-11-04 13:48 UTC (permalink / raw)
To: qemu-devel; +Cc: qemu-trivial, armbru, crobinso
Using access() is a time-of-check/time-of-use race condition. It is
okay to use them to provide better error messages, but that is pretty
much it.
This is not one such case; on the other hand, access() *will* skip
unlink() for a non-existent path, so ignore ENOENT return values from
the unlink() system call.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
util/qemu-sockets.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c
index 9142917..de9145a 100644
--- a/util/qemu-sockets.c
+++ b/util/qemu-sockets.c
@@ -751,8 +751,7 @@ int unix_listen_opts(QemuOpts *opts, Error **errp)
qemu_opt_set(opts, "path", un.sun_path, &error_abort);
}
- if ((access(un.sun_path, F_OK) == 0) &&
- unlink(un.sun_path) < 0) {
+ if (unlink(un.sun_path) < 0 && errno != ENOENT) {
error_setg_errno(errp, errno,
"Failed to unlink socket %s", un.sun_path);
goto err;
--
2.5.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [Qemu-devel] [PATCH v2] qemu-sockets: do not test path with access() before unlinking
2015-11-04 13:48 [Qemu-devel] [PATCH v2] qemu-sockets: do not test path with access() before unlinking Paolo Bonzini
@ 2015-11-04 14:08 ` Markus Armbruster
2015-11-04 14:15 ` Edgar E. Iglesias
2015-11-06 8:05 ` Michael Tokarev
2 siblings, 0 replies; 4+ messages in thread
From: Markus Armbruster @ 2015-11-04 14:08 UTC (permalink / raw)
To: Paolo Bonzini; +Cc: qemu-trivial, qemu-devel, crobinso
Paolo Bonzini <pbonzini@redhat.com> writes:
> Using access() is a time-of-check/time-of-use race condition. It is
> okay to use them to provide better error messages, but that is pretty
> much it.
>
> This is not one such case; on the other hand, access() *will* skip
> unlink() for a non-existent path, so ignore ENOENT return values from
> the unlink() system call.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> util/qemu-sockets.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c
> index 9142917..de9145a 100644
> --- a/util/qemu-sockets.c
> +++ b/util/qemu-sockets.c
> @@ -751,8 +751,7 @@ int unix_listen_opts(QemuOpts *opts, Error **errp)
> qemu_opt_set(opts, "path", un.sun_path, &error_abort);
> }
>
> - if ((access(un.sun_path, F_OK) == 0) &&
> - unlink(un.sun_path) < 0) {
> + if (unlink(un.sun_path) < 0 && errno != ENOENT) {
> error_setg_errno(errp, errno,
> "Failed to unlink socket %s", un.sun_path);
> goto err;
Reviewed-by: Markus Armbruster <armbru@redhat.com>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [Qemu-devel] [PATCH v2] qemu-sockets: do not test path with access() before unlinking
2015-11-04 13:48 [Qemu-devel] [PATCH v2] qemu-sockets: do not test path with access() before unlinking Paolo Bonzini
2015-11-04 14:08 ` Markus Armbruster
@ 2015-11-04 14:15 ` Edgar E. Iglesias
2015-11-06 8:05 ` Michael Tokarev
2 siblings, 0 replies; 4+ messages in thread
From: Edgar E. Iglesias @ 2015-11-04 14:15 UTC (permalink / raw)
To: Paolo Bonzini; +Cc: qemu-trivial, crobinso, qemu-devel, armbru
On Wed, Nov 04, 2015 at 02:48:47PM +0100, Paolo Bonzini wrote:
> Using access() is a time-of-check/time-of-use race condition. It is
> okay to use them to provide better error messages, but that is pretty
> much it.
>
> This is not one such case; on the other hand, access() *will* skip
> unlink() for a non-existent path, so ignore ENOENT return values from
> the unlink() system call.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
> ---
> util/qemu-sockets.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c
> index 9142917..de9145a 100644
> --- a/util/qemu-sockets.c
> +++ b/util/qemu-sockets.c
> @@ -751,8 +751,7 @@ int unix_listen_opts(QemuOpts *opts, Error **errp)
> qemu_opt_set(opts, "path", un.sun_path, &error_abort);
> }
>
> - if ((access(un.sun_path, F_OK) == 0) &&
> - unlink(un.sun_path) < 0) {
> + if (unlink(un.sun_path) < 0 && errno != ENOENT) {
> error_setg_errno(errp, errno,
> "Failed to unlink socket %s", un.sun_path);
> goto err;
> --
> 2.5.0
>
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [Qemu-devel] [PATCH v2] qemu-sockets: do not test path with access() before unlinking
2015-11-04 13:48 [Qemu-devel] [PATCH v2] qemu-sockets: do not test path with access() before unlinking Paolo Bonzini
2015-11-04 14:08 ` Markus Armbruster
2015-11-04 14:15 ` Edgar E. Iglesias
@ 2015-11-06 8:05 ` Michael Tokarev
2 siblings, 0 replies; 4+ messages in thread
From: Michael Tokarev @ 2015-11-06 8:05 UTC (permalink / raw)
To: Paolo Bonzini, qemu-devel; +Cc: qemu-trivial, armbru, crobinso
04.11.2015 16:48, Paolo Bonzini wrote:
> Using access() is a time-of-check/time-of-use race condition. It is
> okay to use them to provide better error messages, but that is pretty
> much it.
Applied to -trivial, thanks!
/mjt
^ permalink raw reply [flat|nested] 4+ messages in thread
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2015-11-04 13:48 [Qemu-devel] [PATCH v2] qemu-sockets: do not test path with access() before unlinking Paolo Bonzini
2015-11-04 14:08 ` Markus Armbruster
2015-11-04 14:15 ` Edgar E. Iglesias
2015-11-06 8:05 ` Michael Tokarev
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