From: Andrii Nakryiko <andrii@kernel.org>
To: bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net,
	martin.lau@kernel.org
Cc: andrii@kernel.org, kernel-team@meta.com,
	Lennart Poettering <lennart@poettering.net>
Subject: [PATCH bpf-next] libbpf: keep FD_CLOEXEC flag when dup()'ing FD
Date: Wed, 29 May 2024 15:32:39 -0700	[thread overview]
Message-ID: <20240529223239.504241-1-andrii@kernel.org> (raw)

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@poettering.net>
Fixes: bc308d011ab8 ("libbpf: call dup2() syscall directly")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 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

next             reply	other threads:[~2024-05-29 22:32 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-05-29 22:32 Andrii Nakryiko [this message]
2024-05-30  7:12 ` [PATCH bpf-next] libbpf: keep FD_CLOEXEC flag when dup()'ing FD Jiri Olsa
2024-05-30  8:56 ` Lennart Poettering
2024-06-03 21:16   ` Andrii Nakryiko
2024-06-01  3:40 ` patchwork-bot+netdevbpf

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