From c9883ee9d110703ccb3dfe2ca13e0b7a01351077 Mon Sep 17 00:00:00 2001 From: Xin Liu Date: Sat, 10 Dec 2022 16:20:45 +0800 Subject: [PATCH] libbpf: Optimized return value in libbpf_strerror when errno is libbpf errno This is a small improvement in libbpf_strerror. When libbpf_strerror is used to obtain the system error description, if the length of the buf is insufficient, libbpf_sterror returns ERANGE and sets errno to ERANGE. However, this processing is not performed when the error code customized by libbpf is obtained. Make some minor improvements here, return -ERANGE and set errno to ERANGE when buf is not enough for custom description. Signed-off-by: Xin Liu Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20221210082045.233697-1-liuxin350@huawei.com --- tools/lib/bpf/libbpf_errno.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/tools/lib/bpf/libbpf_errno.c b/tools/lib/bpf/libbpf_errno.c index 96f67a772a1b..6b180172ec6b 100644 --- a/tools/lib/bpf/libbpf_errno.c +++ b/tools/lib/bpf/libbpf_errno.c @@ -39,14 +39,14 @@ static const char *libbpf_strerror_table[NR_ERRNO] = { int libbpf_strerror(int err, char *buf, size_t size) { + int ret; + if (!buf || !size) return libbpf_err(-EINVAL); err = err > 0 ? err : -err; if (err < __LIBBPF_ERRNO__START) { - int ret; - ret = strerror_r(err, buf, size); buf[size - 1] = '\0'; return libbpf_err_errno(ret); @@ -56,12 +56,20 @@ int libbpf_strerror(int err, char *buf, size_t size) const char *msg; msg = libbpf_strerror_table[ERRNO_OFFSET(err)]; - snprintf(buf, size, "%s", msg); + ret = snprintf(buf, size, "%s", msg); buf[size - 1] = '\0'; + /* The length of the buf and msg is positive. + * A negative number may be returned only when the + * size exceeds INT_MAX. Not likely to appear. + */ + if (ret >= size) + return libbpf_err(-ERANGE); return 0; } - snprintf(buf, size, "Unknown libbpf error %d", err); + ret = snprintf(buf, size, "Unknown libbpf error %d", err); buf[size - 1] = '\0'; + if (ret >= size) + return libbpf_err(-ERANGE); return libbpf_err(-ENOENT); } -- 2.11.0