Linux toolchain unpack leaves bin/* without execute permission (644)

Summary

After rustup update / toolchain install on Linux, binaries under $RUSTUP_HOME/toolchains/*/bin/ can be installed with mode 644 (-rw-r--r--) instead of 755, causing immediate failures:

error: Permission denied (os error 13)

when invoking cargo, rustc, rustfmt, etc.

Environment

• OS: Linux x86_64 (ext4)
• rustup: 1.29.0 (28d1352db 2026-03-05)
• RUSTUP_HOME: ~/.rustup (default)
• umask: 022
• Reproduced: 2026-06-08 after rustup update stable

Steps to reproduce

rustup --version
rustup update stable   # or: rustup toolchain install stable

find "$RUSTUP_HOME/toolchains" -path '*/bin/*' -type f ! -perm -111 -print | head
stat -c '%a %n' "$RUSTUP_HOME/toolchains/stable-x86_64-unknown-linux-gnu/bin/cargo"

cargo --version   # may fail with os error 13 if 644

Expected behaviour

Toolchain binaries under toolchains/*/bin/ are executable (mode includes +x, typically 755 with umask 022).

Actual behaviour

Some or all toolchain bin/* files are 644. The rustup shim itself remains executable; only unpacked toolchain components are affected.

Impact

Breaks CI runners and automation that calls cargo/rustfmt immediately after a toolchain refresh.

Workaround

find "$RUSTUP_HOME/toolchains" -path '*/bin/*' -type f ! -perm -111 -exec chmod +x {} +

Additional notes

• Default ~/.rustup was used (no custom relocation).
• Historical toolchains on the same host also showed 644 on bin/*, suggesting unpack/install rather than backup restore.

Reproduce with rustup update stable or rustup toolchain install stable, then inspect $RUSTUP_HOME/toolchains/*/bin/* using find and stat as shown. Trace the toolchain install/unpack path to determine where executable permissions are lost; done means toolchain binaries retain execute permission and cargo --version works immediately after installation.