[PATCH bpf-next 1/2] libbpf: ensure libbpf always opens files with O_CLOEXEC

[Andrii Nakryiko <andrii@xxxxxxxxxx>]

Make sure that libbpf code always gets FD with O_CLOEXEC flag set,
regardless if file is open through open() or fopen(). For the latter
this means to add "e" to mode string, which is supported since pretty
ancient glibc v2.7.

I also dropped outdated TODO comment in usdt.c, which was already completed.

Suggested-by: Lennart Poettering <lennart@xxxxxxxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
 tools/lib/bpf/btf.c           | 2 +-
 tools/lib/bpf/libbpf.c        | 6 +++---
 tools/lib/bpf/libbpf_probes.c | 2 +-
 tools/lib/bpf/usdt.c          | 5 ++---
 4 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 0a2c079244b6..8484b563b53d 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1064,7 +1064,7 @@ static struct btf *btf_parse_raw(const char *path, struct btf *base_btf)
 	int err = 0;
 	long sz;
 
-	f = fopen(path, "rb");
+	f = fopen(path, "rbe");
 	if (!f) {
 		err = -errno;
 		goto err_out;
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 1ceb3a97dadc..60ef4c5e3bee 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4351,7 +4351,7 @@ static int bpf_get_map_info_from_fdinfo(int fd, struct bpf_map_info *info)
 	snprintf(file, sizeof(file), "/proc/%d/fdinfo/%d", getpid(), fd);
 	memset(info, 0, sizeof(*info));
 
-	fp = fopen(file, "r");
+	fp = fopen(file, "re");
 	if (!fp) {
 		err = -errno;
 		pr_warn("failed to open %s: %d. No procfs support?\n", file,
@@ -7455,7 +7455,7 @@ int libbpf_kallsyms_parse(kallsyms_cb_t cb, void *ctx)
 	int ret, err = 0;
 	FILE *f;
 
-	f = fopen("/proc/kallsyms", "r");
+	f = fopen("/proc/kallsyms", "re");
 	if (!f) {
 		err = -errno;
 		pr_warn("failed to open /proc/kallsyms: %d\n", err);
@@ -10075,7 +10075,7 @@ static int parse_uint_from_file(const char *file, const char *fmt)
 	int err, ret;
 	FILE *f;
 
-	f = fopen(file, "r");
+	f = fopen(file, "re");
 	if (!f) {
 		err = -errno;
 		pr_debug("failed to open '%s': %s\n", file,
diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
index 6065f408a59c..5f78a023b474 100644
--- a/tools/lib/bpf/libbpf_probes.c
+++ b/tools/lib/bpf/libbpf_probes.c
@@ -38,7 +38,7 @@ static __u32 get_ubuntu_kernel_version(void)
 	if (faccessat(AT_FDCWD, ubuntu_kver_file, R_OK, AT_EACCESS) != 0)
 		return 0;
 
-	f = fopen(ubuntu_kver_file, "r");
+	f = fopen(ubuntu_kver_file, "re");
 	if (!f)
 		return 0;
 
diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c
index 086eef355ab3..f1a141555f08 100644
--- a/tools/lib/bpf/usdt.c
+++ b/tools/lib/bpf/usdt.c
@@ -466,7 +466,7 @@ static int parse_vma_segs(int pid, const char *lib_path, struct elf_seg **segs,
 
 proceed:
 	sprintf(line, "/proc/%d/maps", pid);
-	f = fopen(line, "r");
+	f = fopen(line, "re");
 	if (!f) {
 		err = -errno;
 		pr_warn("usdt: failed to open '%s' to get base addr of '%s': %d\n",
@@ -954,8 +954,7 @@ struct bpf_link *usdt_manager_attach_usdt(struct usdt_manager *man, const struct
 	spec_map_fd = bpf_map__fd(man->specs_map);
 	ip_map_fd = bpf_map__fd(man->ip_to_spec_id_map);
 
-	/* TODO: perform path resolution similar to uprobe's */
-	fd = open(path, O_RDONLY);
+	fd = open(path, O_RDONLY | O_CLOEXEC);
 	if (fd < 0) {
 		err = -errno;
 		pr_warn("usdt: failed to open ELF binary '%s': %d\n", path, err);
-- 
2.34.1