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linux-user: Use qemu_set_cloexec() to mark pidfd as FD_CLOEXEC

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In the linux-user do_fork() function we try to set the FD_CLOEXEC
flag on a pidfd like this:

    fcntl(pid_fd, F_SETFD, fcntl(pid_fd, F_GETFL) | FD_CLOEXEC);

This has two problems:
 (1) it doesn't check errors, which Coverity complains about
 (2) we use F_GETFL when we mean F_GETFD

Deal with both of these problems by using qemu_set_cloexec() instead.
That function will assert() if the fcntls fail, which is fine (we are
inside fork_start()/fork_end() so we know nothing can mess around
with our file descriptors here, and we just got this one from
pidfd_open()).

(As we are touching the if() statement here, we correct the
indentation.)

Coverity: CID 1508111
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20250711141217.1429412-1-peter.maydell@linaro.org>
This commit is contained in:
Peter Maydell
2025-07-11 15:12:17 +01:00
committed by Richard Henderson
parent c86da2b1dd
commit d6390204c6
1 changed files with 2 additions and 3 deletions
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5
linux-user/syscall.c
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@@ -6747,10 +6747,9 @@ static int do_fork(CPUArchState *env, unsigned int flags, abi_ulong newsp,
int pid_child = ret;
pid_fd = pidfd_open(pid_child, 0);
if (pid_fd >= 0) {
fcntl(pid_fd, F_SETFD, fcntl(pid_fd, F_GETFL)
| FD_CLOEXEC);
qemu_set_cloexec(pid_fd);
} else {
pid_fd = 0;
pid_fd = 0;
}
#endif
put_user_u32(pid_fd, parent_tidptr);