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Re: [Qemu-devel] [PATCH v2] qemu-sockets: do not test path with access()
From: |
Edgar E. Iglesias |
Subject: |
Re: [Qemu-devel] [PATCH v2] qemu-sockets: do not test path with access() before unlinking |
Date: |
Wed, 4 Nov 2015 15:15:46 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
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 <address@hidden>
Reviewed-by: Edgar E. Iglesias <address@hidden>
> ---
> 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
>
>