Commit 07453245 authored by Xin Liu's avatar Xin Liu Committed by Alexei Starovoitov
Browse files

libbpf: fix errno is overwritten after being closed. 



In the ensure_good_fd function, if the fcntl function succeeds but
the close function fails, ensure_good_fd returns a normal fd and
sets errno, which may cause users to misunderstand. The close
failure is not a serious problem, and the correct FD has been
handed over to the upper-layer application. Let's restore errno here.

Signed-off-by: default avatarXin Liu <liuxin350@huawei.com>
Link: https://lore.kernel.org/r/20221223133618.10323-1-liuxin350@huawei.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 4633a006

tools/lib/bpf/libbpf_internal.h

+2 −3
Original line number Diff line number Diff line
@@ -543,10 +543,9 @@ static inline int ensure_good_fd(int fd) 
		fd = fcntl(fd, F_DUPFD_CLOEXEC, 3);

		saved_errno = errno;

		close(old_fd);

		if (fd < 0) {

			pr_warn("failed to dup FD %d to FD > 2: %d\n", old_fd, -saved_errno);

		errno = saved_errno;

		}

		if (fd < 0)

			pr_warn("failed to dup FD %d to FD > 2: %d\n", old_fd, -saved_errno);

	}

	return fd;

}