linux-kernel - Re: [PATCH][CFT] [coredump] don't use __kernel_write() on kmap_local

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Date:   Tue, 4 Oct 2022 00:37:16 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     "J. R. Okajima" <hooanon05g@...il.com>
Cc:     Ira Weiny <ira.weiny@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH][CFT] [coredump] don't use __kernel_write() on
 kmap_local_page()

On Tue, Oct 04, 2022 at 07:58:14AM +0900, J. R. Okajima wrote:
> Al Viro:
> > Argh....  Try this:
> >
> > fix coredump breakage caused by badly tested "[coredump] don't use __kernel_write() on kmap_local_page()"
> 
> Thanx, it passed my local test.
> 
> 
> > * fix for problem that occurs on rather uncommon setups (and hadn't
> > been observed in the wild) sent very late in the cycle.
> 
> If the commit was merged in RC versions, I guess someone found the
> problem earlier.

Most likely - the breakage is really not hard to trigger ;-/

	Linus, which way would you prefer to handle that?  It's
a brown paperbag stuff - the worst I had in quite a while.
Mea maxima culpa ;-/

One variant would be to revert the original patch, put its
(hopefully) fixed variant into -next and let it sit there for
a while.  Another is to put this incremental into -next and
merge it into mainline once it gets a sane amount of testing.

	Up to you...