From: Greg KH <gregkh@linuxfoundation.org>
To: Yichong Chen <chenyichong@uniontech.com>
Cc: jirislaby@kernel.org, viro@zeniv.linux.org.uk,
willy@infradead.org, kees@kernel.org,
linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] devpts: fix pty count limit off by one
Date: Tue, 4 Aug 2026 10:40:26 +0200 [thread overview]
Message-ID: <2026080419-chatting-curve-e49c@gregkh> (raw)
In-Reply-To: <20260804082321.884880-1-chenyichong@uniontech.com>
On Tue, Aug 04, 2026 at 04:23:21PM +0800, Yichong Chen wrote:
> devpts_new_index() increments the global pty count before checking it
> against the effective global limit. The check currently rejects a new pty
> when the incremented count is equal to the limit.
>
> This makes kernel.pty.max allow only max - 1 ptys. For example, if
> kernel.pty.nr is 3 and kernel.pty.max is set to 4, opening /dev/ptmx
> fails with -ENOSPC even though one more pty should be allowed.
>
> Allow the incremented count to be equal to the effective limit and reject
> only counts above it.
>
> Fixes: 0f0a0e54a2a1 ("devpts: Convert to new IDA API")
As this is a user-visible change, what is now going to break because of
this? It's been this way for a very long time now.
thanks,
greg k-h
next prev parent reply other threads:[~2026-08-04 8:40 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-04 8:23 Yichong Chen
2026-08-04 8:40 ` Greg KH [this message]
2026-08-04 9:52 ` Yichong Chen
2026-08-04 10:06 ` Greg KH
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