From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by passt.top (Postfix) with ESMTP id 190325A0265 for ; Thu, 13 Oct 2022 04:17:28 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1665627447; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=8OEBeFIx5rkX4fj4fLGtV6wBVTeyn4EV5XgXnziFZp8=; b=Gb7gLTQeJFIbXgSMO0AulI4IrCrTKvI4uB/MvFt+0YG9b17A8/B9OF1PALqW16YlWlHAxr EKT5iwZ6fP9Zsx9c6cDiJ0NecjisRcw4hkU084eQEkZJ+Xuc8FI4EiH7bvprYND7YscN9n 902+XsiOtHaScGUvb8wWoZH0qB8WTQY= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-101-pRtVh44GMHy2HYynnz6CbA-1; Wed, 12 Oct 2022 22:17:23 -0400 X-MC-Unique: pRtVh44GMHy2HYynnz6CbA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 5E70229AB3F2; Thu, 13 Oct 2022 02:17:23 +0000 (UTC) Received: from maya.cloud.tilaa.com (ovpn-208-3.brq.redhat.com [10.40.208.3]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 99614208746C; Thu, 13 Oct 2022 02:17:14 +0000 (UTC) Date: Thu, 13 Oct 2022 04:17:09 +0200 From: Stefano Brivio To: David Gibson Subject: Re: [PATCH 06/10] Replace FWRITE with a function Message-ID: <20221013041709.316ec052@elisabeth> In-Reply-To: <20221011054018.1449506-7-david@gibson.dropbear.id.au> References: <20221011054018.1449506-1-david@gibson.dropbear.id.au> <20221011054018.1449506-7-david@gibson.dropbear.id.au> Organization: Red Hat MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-ID-Hash: SXUTO6Q3XEEUPNWH6ZJKAIY6PVC2MXGN X-Message-ID-Hash: SXUTO6Q3XEEUPNWH6ZJKAIY6PVC2MXGN X-MailFrom: sbrivio@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-dev@passt.top X-Mailman-Version: 3.3.3 Precedence: list List-Id: Development discussion and patches for passt Archived-At: <> Archived-At: List-Archive: <> List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Tue, 11 Oct 2022 16:40:14 +1100 David Gibson wrote: > In a few places we use the FWRITE() macro to open a file, replace it's > contents with a given string and close it again. There's no real > reason this needs to be a macro rather than just a function though. Well, there's a bit of a reason: it gives more descriptive messages in isolate_user() with the same LoCs. On the other hand I would also prefer a function here, probably better than the alternative I'm not sure why this series needs this by the way. > Turn it into a function 'write_file()' and make some ancillary > cleanups while we're there: > - Add a return code so the caller can handle giving a useful error message > - Handle the case of short write()s (unlikely, but possible) > - Add O_TRUNC, to make sure we replace the existing contents entirely > > Signed-off-by: David Gibson > --- > isolation.c | 17 +++++++++-------- > pasta.c | 4 ++-- > util.c | 33 +++++++++++++++++++++++++++++++++ > util.h | 13 +------------ > 4 files changed, 45 insertions(+), 22 deletions(-) > > diff --git a/isolation.c b/isolation.c > index 10cef05..4aa75e6 100644 > --- a/isolation.c > +++ b/isolation.c > @@ -129,7 +129,8 @@ void isolate_initial(void) > */ > void isolate_user(uid_t uid, gid_t gid, bool use_userns, const char *userns) > { > - char nsmap[BUFSIZ]; > + char uidmap[BUFSIZ]; > + char gidmap[BUFSIZ]; > > /* First set our UID & GID in the original namespace */ > if (setgroups(0, NULL)) { > @@ -184,14 +185,14 @@ void isolate_user(uid_t uid, gid_t gid, bool use_userns, const char *userns) > } > > /* Configure user and group mappings */ > - snprintf(nsmap, BUFSIZ, "0 %u 1", uid); > - FWRITE("/proc/self/uid_map", nsmap, "Cannot set uid_map in namespace"); > + snprintf(uidmap, BUFSIZ, "0 %u 1", uid); > + snprintf(gidmap, BUFSIZ, "0 %u 1", gid); > > - FWRITE("/proc/self/setgroups", "deny", > - "Cannot write to setgroups in namespace"); > - > - snprintf(nsmap, BUFSIZ, "0 %u 1", gid); > - FWRITE("/proc/self/gid_map", nsmap, "Cannot set gid_map in namespace"); > + if (write_file("/proc/self/uid_map", uidmap) || > + write_file("/proc/self/setgroups", "deny") || > + write_file("/proc/self/gid_map", gidmap)) { > + warn("Couldn't configure user namespace"); It's unlikely that we can write to uid_map but not to setgroups. Still, having separate messages, as we had them, could help investigating some issues. > + } > } > > /** > diff --git a/pasta.c b/pasta.c > index 4ff322c..0ab2fe4 100644 > --- a/pasta.c > +++ b/pasta.c > @@ -167,8 +167,8 @@ static int pasta_setup_ns(void *arg) > const struct pasta_setup_ns_arg *a > = (const struct pasta_setup_ns_arg *)arg; > > - FWRITE("/proc/sys/net/ipv4/ping_group_range", "0 0", > - "Cannot set ping_group_range, ICMP requests might fail"); > + if (write_file("/proc/sys/net/ipv4/ping_group_range", "0 0")) > + warn("Cannot set ping_group_range, ICMP requests might fail"); > > execvp(a->exe, a->argv); > > diff --git a/util.c b/util.c > index 6b86ead..93b93b1 100644 > --- a/util.c > +++ b/util.c > @@ -547,3 +547,36 @@ int fls(unsigned long x) > > return y; > } > + > +/** > + * write_file() - Replace contents of file with a string > + * @path: File to write > + * @buf: String to write > + * > + * Return: 0 on success, -1 on any error > + */ > +int write_file(const char *path, const char *buf) We could also use this for the PID file by optionally taking a file number, but I haven't tried how it looks like. > +{ > + int fd = open(path, O_WRONLY | O_TRUNC | O_CLOEXEC); > + size_t len = strlen(buf); > + > + if (fd < 0) { > + warn("Could not open %s: %s", path, strerror(errno)); > + return -1; > + } > + > + while (len) { > + ssize_t rc = write(fd, buf, len); > + > + if (rc < 0) { I would change this to <= 0. Not that it matters with write(), but should we ever change that another function, we run the (absolutely not critical) risk of forgetting to adjust this and get stuck in a loop here. > + warn("Couldn't write to %s: %s", path, strerror(errno)); > + break; > + } > + > + buf += rc; > + len -= rc; > + } > + > + close(fd); > + return len == 0 ? 0 : -1; > +} > diff --git a/util.h b/util.h > index 0c06e34..f957522 100644 > --- a/util.h > +++ b/util.h > @@ -58,18 +58,6 @@ void trace_init(int enable); > #define TMPDIR "/tmp" > #endif > > -#define FWRITE(path, buf, str) \ > - do { \ > - int flags = O_WRONLY | O_CLOEXEC; \ > - int fd = open(path, flags); \ > - \ > - if (fd < 0 || \ > - write(fd, buf, strlen(buf)) != (int)strlen(buf)) \ > - warn(str); \ > - if (fd >= 0) \ > - close(fd); \ > - } while (0) > - > #define V4 0 > #define V6 1 > #define IP_VERSIONS 2 > @@ -215,5 +203,6 @@ int ns_enter(const struct ctx *c); > void write_pidfile(int fd, pid_t pid); > int __daemon(int pidfile_fd, int devnull_fd); > int fls(unsigned long x); > +int write_file(const char *path, const char *buf); > > #endif /* UTIL_H */ -- Stefano