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Date: Fri, 4 Nov 2022 09:27:54 +0800
From: Rong Tao <rtoax@...mail.com>
To: andrii.nakryiko@...il.com
Cc: andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org,
daniel@...earbox.net, david.laight@...lab.com, haoluo@...gle.com,
john.fastabend@...il.com, jolsa@...nel.org, kpsingh@...nel.org,
linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
martin.lau@...ux.dev, mykolal@...com, rongtao@...tc.cn,
rtoax@...mail.com, sdf@...gle.com, shuah@...nel.org,
song@...nel.org, yhs@...com
Subject: [PATCH bpf-next] selftests/bpf: cgroup_helpers.c: Fix strncpy() fortify warning
From: Rong Tao <rongtao@...tc.cn>
Copy libbpf_strlcpy() from libbpf_internal.h to bpf_util.h, and rename it
to bpf_strlcpy(), then replace selftests strncpy()/libbpf_strlcpy() with
bpf_strlcpy(), fix compile warning.
The libbpf_internal.h header cannot be used directly here, because
references to cgroup_helpers.c in samples/bpf will generate compilation
errors. We also can't add libbpf_strlcpy() directly to bpf_util.h,
because the definition of libbpf_strlcpy() in libbpf_internal.h is
duplicated. In order not to modify the libbpf code, add a new function
bpf_strlcpy() to selftests bpf_util.h.
How to reproduce this compilation warning:
$ make -C samples/bpf
cgroup_helpers.c: In function ‘__enable_controllers’:
cgroup_helpers.c:80:17: warning: ‘strncpy’ specified bound 4097 equals destination size [-Wstringop-truncation]
80 | strncpy(enable, controllers, sizeof(enable));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Signed-off-by: Rong Tao <rongtao@...tc.cn>
---
tools/testing/selftests/bpf/bpf_util.h | 19 ++++++++++++++
tools/testing/selftests/bpf/cgroup_helpers.c | 3 ++-
tools/testing/selftests/bpf/xsk.c | 26 +++-----------------
3 files changed, 25 insertions(+), 23 deletions(-)
diff --git a/tools/testing/selftests/bpf/bpf_util.h b/tools/testing/selftests/bpf/bpf_util.h
index a3352a64c067..10587a29b967 100644
--- a/tools/testing/selftests/bpf/bpf_util.h
+++ b/tools/testing/selftests/bpf/bpf_util.h
@@ -20,6 +20,25 @@ static inline unsigned int bpf_num_possible_cpus(void)
return possible_cpus;
}
+/* Copy up to sz - 1 bytes from zero-terminated src string and ensure that dst
+ * is zero-terminated string no matter what (unless sz == 0, in which case
+ * it's a no-op). It's conceptually close to FreeBSD's strlcpy(), but differs
+ * in what is returned. Given this is internal helper, it's trivial to extend
+ * this, when necessary. Use this instead of strncpy inside libbpf source code.
+ */
+static inline void bpf_strlcpy(char *dst, const char *src, size_t sz)
+{
+ size_t i;
+
+ if (sz == 0)
+ return;
+
+ sz--;
+ for (i = 0; i < sz && src[i]; i++)
+ dst[i] = src[i];
+ dst[i] = '\0';
+}
+
#define __bpf_percpu_val_align __attribute__((__aligned__(8)))
#define BPF_DECLARE_PERCPU(type, name) \
diff --git a/tools/testing/selftests/bpf/cgroup_helpers.c b/tools/testing/selftests/bpf/cgroup_helpers.c
index e914cc45b766..dd1aa5afcf5a 100644
--- a/tools/testing/selftests/bpf/cgroup_helpers.c
+++ b/tools/testing/selftests/bpf/cgroup_helpers.c
@@ -13,6 +13,7 @@
#include <ftw.h>
#include "cgroup_helpers.h"
+#include "bpf_util.h"
/*
* To avoid relying on the system setup, when setup_cgroup_env is called
@@ -77,7 +78,7 @@ static int __enable_controllers(const char *cgroup_path, const char *controllers
enable[len] = 0;
close(fd);
} else {
- strncpy(enable, controllers, sizeof(enable));
+ bpf_strlcpy(enable, controllers, sizeof(enable));
}
snprintf(path, sizeof(path), "%s/cgroup.subtree_control", cgroup_path);
diff --git a/tools/testing/selftests/bpf/xsk.c b/tools/testing/selftests/bpf/xsk.c
index 0b3ff49c740d..39d349509ba4 100644
--- a/tools/testing/selftests/bpf/xsk.c
+++ b/tools/testing/selftests/bpf/xsk.c
@@ -33,6 +33,7 @@
#include <bpf/bpf.h>
#include <bpf/libbpf.h>
#include "xsk.h"
+#include "bpf_util.h"
#ifndef SOL_XDP
#define SOL_XDP 283
@@ -521,25 +522,6 @@ static int xsk_create_bpf_link(struct xsk_socket *xsk)
return 0;
}
-/* Copy up to sz - 1 bytes from zero-terminated src string and ensure that dst
- * is zero-terminated string no matter what (unless sz == 0, in which case
- * it's a no-op). It's conceptually close to FreeBSD's strlcpy(), but differs
- * in what is returned. Given this is internal helper, it's trivial to extend
- * this, when necessary. Use this instead of strncpy inside libbpf source code.
- */
-static inline void libbpf_strlcpy(char *dst, const char *src, size_t sz)
-{
- size_t i;
-
- if (sz == 0)
- return;
-
- sz--;
- for (i = 0; i < sz && src[i]; i++)
- dst[i] = src[i];
- dst[i] = '\0';
-}
-
static int xsk_get_max_queues(struct xsk_socket *xsk)
{
struct ethtool_channels channels = { .cmd = ETHTOOL_GCHANNELS };
@@ -552,7 +534,7 @@ static int xsk_get_max_queues(struct xsk_socket *xsk)
return -errno;
ifr.ifr_data = (void *)&channels;
- libbpf_strlcpy(ifr.ifr_name, ctx->ifname, IFNAMSIZ);
+ bpf_strlcpy(ifr.ifr_name, ctx->ifname, IFNAMSIZ);
err = ioctl(fd, SIOCETHTOOL, &ifr);
if (err && errno != EOPNOTSUPP) {
ret = -errno;
@@ -771,7 +753,7 @@ static int xsk_create_xsk_struct(int ifindex, struct xsk_socket *xsk)
}
ctx->ifindex = ifindex;
- libbpf_strlcpy(ctx->ifname, ifname, IFNAMSIZ);
+ bpf_strlcpy(ctx->ifname, ifname, IFNAMSIZ);
xsk->ctx = ctx;
xsk->ctx->has_bpf_link = xsk_probe_bpf_link();
@@ -958,7 +940,7 @@ static struct xsk_ctx *xsk_create_ctx(struct xsk_socket *xsk,
ctx->refcount = 1;
ctx->umem = umem;
ctx->queue_id = queue_id;
- libbpf_strlcpy(ctx->ifname, ifname, IFNAMSIZ);
+ bpf_strlcpy(ctx->ifname, ifname, IFNAMSIZ);
ctx->fill = fill;
ctx->comp = comp;
--
2.31.1
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