linux-kernel - Re: [PATCH 4.19] Revert "initramfs: free initrd memory if opening /initrd.image fails"

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Date:   Tue, 06 Aug 2019 14:36:45 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Sasha Levin <sashal@...nel.org>
Cc:     stable@...r.kernel.org, linux-kernel@...r.kernel.org,
        Steven Price <steven.price@....com>,
        Mark Rutland <mark.rutland@....com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH 4.19] Revert "initramfs: free initrd memory if opening /initrd.image fails"

Quoting Sasha Levin (2019-08-06 13:47:52)
> On Tue, Aug 06, 2019 at 10:59:40AM -0700, Stephen Boyd wrote:
> >This reverts commit 25511676362d8f7d4b8805730a3d29484ceab1ec in the 4.19
> >stable trees. From what I can tell this commit doesn't do anything to
> >improve the situation, mostly just reordering code to call free_initrd()
> >from one place instead of many. In doing that, it causes free_initrd()
> >to be called even in the case when there isn't an initrd present. That
> >leads to virtual memory bugs that manifest on arm64 devices.
> >
> >The fix has been merged upstream in commit 5d59aa8f9ce9 ("initramfs:
> >don't free a non-existent initrd"), but backporting that here is more
> >complicated because the patch is stacked upon this patch being reverted
> >along with more patches that rewrites the logic in this area.
> >
> >Let's just revert the patch from the stable tree instead of trying to
> >backport a collection of fixes to get the final fix from upstream.
> 
> The only dependency for taking the fix, 5d59aa8f9ce9, into 4.19 is
> 23091e28735 ("initramfs: cleanup initrd freeing") which is not too
> scary.
> 
> Is it the case that 25511676362d8 shouldn't have been backported to 4.19
> for some reason? If it fixes something on 4.19, I think it's better to
> take the dependency and the fix instead of reverting.
> 

Ah thanks for taking a second look. I missed that we call free_initrd()
in one more case when unpack_to_rootfs() fails and goes into the else
statement. I suppose bringing in 23091e28735 ("initramfs: cleanup initrd
freeing") in addition to 5d59aa8f9ce9 works just as well, but I'll defer
to the persons working in this area.