linux-kernel - Re: [PATCH] fs: Use a cleanup attribute in copy

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Message-ID: <20251005090152.GE2441659@ZenIV>
Date: Sun, 5 Oct 2025 10:01:52 +0100
From: Al Viro <viro@...iv.linux.org.uk>
To: Miquel Sabaté Solà <mssola@...ola.com>
Cc: linux-fsdevel@...r.kernel.org, brauner@...nel.org,
	linux-kernel@...r.kernel.org, jack@...e.cz
Subject: Re: [PATCH] fs: Use a cleanup attribute in copy_fdtable()

On Sun, Oct 05, 2025 at 07:37:50AM +0200, Miquel Sabaté Solà wrote:
> Al Viro @ 2025-10-04 22:19 +01:
> 
> > On Sat, Oct 04, 2025 at 11:03:40PM +0200, Miquel Sabaté Solà wrote:
> >> This is a small cleanup in which by using the __free(kfree) cleanup
> >> attribute we can avoid three labels to go to, and the code turns to be
> >> more concise and easier to follow.
> >
> > Have you tried to build and boot that?
> 
> Yes, and it worked on my machine...

Unfortunately, it ends up calling that kfree() on success as well as on failure.
Idiomatic way to avoid that would be
	return no_free_ptr(fdt);
but you've left bare
	return fdt;
in there, ending up with returning dangling pointers to the caller.  So as
soon as you get more than BITS_PER_LONG descriptors used by a process,
you'll get trouble.  In particular, bash(1) running as an interactive shell
would hit that - it has descriptor 255 opened...