Commit b3c09fdc authored by Rong Tao's avatar Rong Tao Committed by Andrii Nakryiko
Browse files

selftests/bpf: cgroup_helpers.c: Fix strncpy() fortify warning 



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: default avatarRong Tao <rongtao@cestc.cn>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/tencent_469D8AF32BD56816A29981BED06E96D22506@qq.com
parent 1baa7e38

tools/testing/selftests/bpf/bpf_util.h

+19 −0
Original line number Diff line number Diff line
@@ -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)				\

tools/testing/selftests/bpf/cgroup_helpers.c

+2 −1
Original line number Diff line number Diff line
@@ -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);

tools/testing/selftests/bpf/xsk.c

+4 −22
Original line number Diff line number Diff line
@@ -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;