Make sure to preserve and/or enforce FD_CLOEXEC flag on duped FDs.
Use dup3() with O_CLOEXEC flag for that.
Without this fix libbpf effectively clears FD_CLOEXEC flag on each of BPF
map/prog FD, which is definitely not the right or expected behavior.
Reported-by: Lennart Poettering <lennart@xxxxxxxxxxxxxx>
Fixes: bc308d011ab8 ("libbpf: call dup2() syscall directly")
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
tools/lib/bpf/libbpf_internal.h | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index a0dcfb82e455..7e7e686008c6 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -597,13 +597,9 @@ static inline int ensure_good_fd(int fd)
return fd;
}
-static inline int sys_dup2(int oldfd, int newfd)
+static inline int sys_dup3(int oldfd, int newfd, int flags)
{
-#ifdef __NR_dup2
- return syscall(__NR_dup2, oldfd, newfd);
-#else
- return syscall(__NR_dup3, oldfd, newfd, 0);
-#endif
+ return syscall(__NR_dup3, oldfd, newfd, flags);
}
/* Point *fixed_fd* to the same file that *tmp_fd* points to.
@@ -614,7 +610,7 @@ static inline int reuse_fd(int fixed_fd, int tmp_fd)
{
int err;
- err = sys_dup2(tmp_fd, fixed_fd);
+ err = sys_dup3(tmp_fd, fixed_fd, O_CLOEXEC);
err = err < 0 ? -errno : 0;
close(tmp_fd); /* clean up temporary FD */
return err;
--
2.43.0
