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libbpf: keep FD_CLOEXEC flag when dup()'ing FD

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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: bc308d011a ("libbpf: call dup2() syscall directly")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20240529223239.504241-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2024-05-29 15:32:39 -07:00 committed by Alexei Starovoitov
parent 3f8fde3195
commit 531876c800
1 changed files with 3 additions and 7 deletions
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10
tools/lib/bpf/libbpf_internal.h
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@ -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;