linux-kernel - Re: [PATCH v3] pipe: Fix memory leaks in create_pipe

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Message-ID: <20201001131659.GE3421308@ZenIV.linux.org.uk>
Date:   Thu, 1 Oct 2020 14:16:59 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Qian Cai <cai@...hat.com>
Cc:     David Howells <dhowells@...hat.com>, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] pipe: Fix memory leaks in create_pipe_files()

On Thu, Oct 01, 2020 at 08:50:55AM -0400, Qian Cai wrote:
> Calling pipe2() with O_NOTIFICATION_PIPE could results in memory leaks
> in an error path or CONFIG_WATCH_QUEUE=n. Plug them.

[snip the copy of bug report]

No objections on the patch itself, but commit message is just about
unreadable.  How about something along the lines of the following?

=======================
	Calling pipe2() with O_NOTIFICATION_PIPE could results in memory
leaks unless watch_queue_init() is successful.

	In case of watch_queue_init() failure in pipe2() we are left
with inode and pipe_inode_info instances that need to be freed.  That
failure exit has been introduced in commit c73be61cede5 ("pipe: Add
general notification queue support") and its handling should've been
identical to nearby treatment of alloc_file_pseudo() failures - it
is dealing with the same situation.  As it is, the mainline kernel
leaks in that case.

	Another problem is that CONFIG_WATCH_QUEUE and !CONFIG_WATCH_QUEUE 
cases are treated differently (and the former leaks just pipe_inode_info,
the latter - both pipe_inode_info and inode).

	Fixed by providing a dummy wath_queue_init() in !CONFIG_WATCH_QUEUE
case and by having failures of wath_queue_init() handled the same way
we handle alloc_file_pseudo() ones.

Fixes: c73be61cede5 ("pipe: Add general notification queue support")
Signed-off-by: Qian Cai <cai@...hat.com>
=======================