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dd incorrectly depends on fcntl syscall #12157

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dd incorrectly depends on fcntl syscall#12157
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U - dd

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@oech3
oech3
opened on May 5, 2026
$ strace -o /dev/null -e inject=fcntl:error=ENOSYS dd if=/etc/pacman.conf
dd: write error
$ strace -o /dev/null -e inject=fcntl:error=ENOSYS '/home/a/bin/gnu9.11/dd' if=/etc/pacman.conf # success

I guess this bug was introduced at #10235
@svlv @ChrisDryden

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  1. xtqqczze commented on May 5, 2026

    @xtqqczze
    xtqqczze
    on May 5, 2026
    Collaborator

    Could you explain a bit more about why it is incorrect?

  2. oech3 commented on May 5, 2026

    @oech3
    oech3
    on May 5, 2026
    ContributorAuthor

    Because GNU success with the provided command.

  3. oech3 commented on May 5, 2026

    @oech3
    oech3
    on May 5, 2026
    ContributorAuthor

    Is it easy to remove try_clone?
    But this is low priority since this would affect to very few containers.

    Rust std should really stop force-breaking stdout and signals by default...

  4. cakebaker
    added
    U - dd
    on May 6, 2026

  5. oech3 commented on May 7, 2026

    @oech3
    oech3
    on May 7, 2026
    ContributorAuthor

    I guess we cannot use rustix::stdio::stdout at here since dd requires seek.

  6. xtqqczze commented on May 7, 2026

    @xtqqczze
    xtqqczze
    on May 7, 2026
    Collaborator

    The usual pattern would be to use a "borrowed" File:

    let mut file = ManuallyDrop::new(unsafe { File::from_raw_fd(raw_fd) });
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