[Bug 1813873] [NEW] Userspace break as a result of missing patch backport

Public bug reported:

Hi,

The most recent set of Ubuntu kernels applied a variety of tty patches
including:
https://github.com/torvalds/linux/commit/c96cf923a98d1b094df9f0cf97a83e118817e31b

But have not applied the more recent
https://github.com/torvalds/linux/commit/d3736d82e8169768218ee0ef68718875918091a0
patch.

This second patch is required to prevent a rather serious regression
where userspace applications reading from stdin can receive EAGAIN when
they should not.

I will try to link correspondence from the mailing list archives once
they are available, but for now if you have access to the linux-console
mailing list you can find discussion under the thread "Userspace break?
read from STDIN returns EAGAIN if tty is "touched"".

I would appreciate it if this could be examined soon as it is a
regression on userspace.

Thanks
Michael


Good:
4.15.0-43-generic #46-Ubuntu SMP Thu Dec 6 14:45:28 UTC 2018


Bad:
4.15.0-44-generic #47-Ubuntu SMP Mon Jan 14 11:26:59 UTC 2019

** Affects: linux (Ubuntu)
Importance: Undecided
Status: Confirmed

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https://bugs.launchpad.net/bugs/1813873

Title:
Userspace break as a result of missing patch backport

Status in linux package in Ubuntu:
Confirmed

Bug description:
Hi,

The most recent set of Ubuntu kernels applied a variety of tty patches
including:
https://github.com/torvalds/linux/commit/c96cf923a98d1b094df9f0cf97a83e118817e31b

But have not applied the more recent
https://github.com/torvalds/linux/commit/d3736d82e8169768218ee0ef68718875918091a0
patch.

This second patch is required to prevent a rather serious regression
where userspace applications reading from stdin can receive EAGAIN
when they should not.

I will try to link correspondence from the mailing list archives once
they are available, but for now if you have access to the linux-
console mailing list you can find discussion under the thread
"Userspace break? read from STDIN returns EAGAIN if tty is "touched"".

I would appreciate it if this could be examined soon as it is a
regression on userspace.

Thanks
Michael


Good:
4.15.0-43-generic #46-Ubuntu SMP Thu Dec 6 14:45:28 UTC 2018


Bad:
4.15.0-44-generic #47-Ubuntu SMP Mon Jan 14 11:26:59 UTC 2019

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