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libbpf: fix errno is overwritten after being closed.

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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: Xin Liu <liuxin350@huawei.com>
Link: https://lore.kernel.org/r/20221223133618.10323-1-liuxin350@huawei.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Xin Liu 2022-12-23 21:36:18 +08:00 committed by Alexei Starovoitov
parent 4633a00682
commit 0745324562
1 changed files with 2 additions and 3 deletions
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5
tools/lib/bpf/libbpf_internal.h
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@ -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) {
errno = saved_errno;
if (fd < 0)
pr_warn("failed to dup FD %d to FD > 2: %d\n", old_fd, -saved_errno);
errno = saved_errno;
}
}
return fd;
}