tee -p (Linux) ensure_stdout_not_broken Can Hang Forever on Pipes

[sylvestre]

Component

tee

Description

On Linux, uutils tee -p calls ensure_stdout_not_broken() which does an infinite poll() on stdout using only POLLRDBAND. On normal pipelines this event never fires, so tee blocks before it starts copying stdin. GNU tee uses iopoll() (stdin + stdout) and does not hang.

Test / Reproduction Steps

echo "test data" | ./target/release/coreutils tee -p /tmp/output.txt | cat

• GNU: test data
• uutils: hangs

Impact

DoS via pipeline deadlock for any Linux workflow using tee -p in pipes (logging pipelines, service wrappers, CI scripts).

[ChrisDryden]

I was unable to replicate this and I was able to find that this PR: #9585 fixed the issue described in the test / reproduction steps