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

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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@cestc.cn>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/tencent_469D8AF32BD56816A29981BED06E96D22506@qq.com
This commit is contained in:
Rong Tao 2022-11-04 09:27:54 +08:00 committed by Andrii Nakryiko
parent 1baa7e3800
commit b3c09fdca1
3 changed files with 25 additions and 23 deletions
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19
tools/testing/selftests/bpf/bpf_util.h
View File

@ -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) \

3
tools/testing/selftests/bpf/cgroup_helpers.c
View File

@ -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);

26
tools/testing/selftests/bpf/xsk.c
View File

@ -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;