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fs: using -EBADF as a dirfd argument #1187

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cyphar opened this issue Oct 17, 2024 · 1 comment · Fixed by #1189
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fs: using -EBADF as a dirfd argument #1187

cyphar opened this issue Oct 17, 2024 · 1 comment · Fixed by #1189

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@cyphar
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cyphar commented Oct 17, 2024 •
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Some programs want to ensure that no paths are resolved relative to the current directory, and so use -EBADF as a file descriptor argument so that an error is returned if the path is not absolute. This is a fairly common pattern, but unfortunately rustix does not allow it:

thread 'utils::fd::tests::metadata_badfd' panicked at /home/cyphar/.cargo/registry/src/index.crates.io-6f17d22bba15001f/rustix-0.38.37/src/backend/linux_raw/conv.rs:165:5:
assertion failed: fd == crate::fs::CWD.as_raw_fd() || fd >= 0
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

The one-line patch for this is fairly straightforward (only disallow -1 since that's an invalid BorrowedFd value) but I wanted to make sure that there wasn't a nicer solution (maybe we should just define a new CWD-like constant akin to no_fd so users can just re-use that).
@cyphar cyphar mentioned this issue Oct 17, 2024
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sunfishcode added a commit that referenced this issue Oct 17, 2024
@sunfishcode
Add a rustix::fs::ABS constant.
1f44e35 
Add a `rustix::fs::ABS` constant, which corresponds to the undocumented
but commonly used convention of using `-EBADF` as the file descriptor in
`openat` and similar calls. This makes them fail if the path is not
absolute.

Fixes #1187.
@sunfishcode sunfishcode mentioned this issue Oct 17, 2024
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@sunfishcode
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sunfishcode commented Oct 17, 2024 •
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Interesting, I hadn't heard of that convention before. I think defining a new CWD-like constant sounds good. I've now posted #1189 with a patch for this.

sunfishcode added a commit that referenced this issue Oct 18, 2024
@sunfishcode
Add a rustix::fs::ABS constant. (#1189)
873bac5 
Add a `rustix::fs::ABS` constant, which corresponds to the undocumented
but commonly used convention of using `-EBADF` as the file descriptor in
`openat` and similar calls. This makes them fail if the path is not
absolute.

Fixes #1187.
sunfishcode added a commit that referenced this issue Oct 27, 2024
@sunfishcode
Add a rustix::fs::ABS constant. (#1189)
e2cbb9f 
Add a `rustix::fs::ABS` constant, which corresponds to the undocumented
but commonly used convention of using `-EBADF` as the file descriptor in
`openat` and similar calls. This makes them fail if the path is not
absolute.

Fixes #1187.
sunfishcode added a commit that referenced this issue Oct 27, 2024
@sunfishcode
Add a rustix::fs::ABS constant. (#1189)
ec78479 
Add a `rustix::fs::ABS` constant, which corresponds to the undocumented
but commonly used convention of using `-EBADF` as the file descriptor in
`openat` and similar calls. This makes them fail if the path is not
absolute.

Fixes #1187.
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Add a rustix::fs::ABS constant. bytecodealliance/rustix
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@cyphar @sunfishcode