Re: [PATCH] kexec: use mmap instead of read for slurp_file()

From: Michael Holzheu <holzheu@linux.vnet.ibm.com>
To: Geoff Levand <geoff@infradead.org>
Cc: stefan.roscher@de.ibm.com, Simon Horman <horms@verge.net.au>,
	kexec@lists.infradead.org
Subject: Re: [PATCH] kexec: use mmap instead of read for slurp_file()
Date: Thu, 15 Oct 2015 14:31:38 +0200	[thread overview]
Message-ID: <20151015143138.1287fd6f@holzheu> (raw)
In-Reply-To: <1444867552.3929.7.camel@infradead.org>

On Wed, 14 Oct 2015 17:05:52 -0700
Geoff Levand <geoff@infradead.org> wrote:

[snip]

> >  		if (err < 0)
> >  > 	> 	> 	> die("Can not seek to the begin of file %s: %s\n",
> >  > 	> 	> 	> 	> 	> filename, strerror(errno));
> > +> 	> 	> buf = slurp_fd(fd, filename, size, &nread);
> >  > 	> } else {
> > -> 	> 	> size = stats.st_size;
> > +> 	> 	> size = nread = stats.st_size;
> > +> 	> 	> buf = mmap(NULL, size,
> 
> With this change the caller can't tell if buf was malloc'ed or mmaped.  The
> only safe thing it can do is to not call free() on the returned buf, this will
> lead to memory leakage for malloc'ed buffers.

I have read the code and have not found any free call. Therefore I assumed
that the kexec approach is to not free the buffer *explicitly* and leave to
the kernel to free it *automatically* at process exit.

@Simon: Was this assumption wrong?

Michael

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