Re: FAILED: patch "[PATCH] lib/crypto: arm64: Fix lost Poly1305 carry when resuming NEON" failed to apply to 6.12-stable tree

[Eric Biggers <ebiggers@kernel.org>]

On Wed, Oct 21, 2026 at 08:48:08AM -0700, Eric Biggers wrote:
> [+Cc linux-crypto@vger.kernel.org]
> 
> On Wed, Oct 21, 2026 at 04:40:37PM +0200, gregkh@linuxfoundation.org wrote:
> > 
> > The patch below does not apply to the 6.12-stable tree.
> > If someone wants it applied there, or to any other stable or longterm
> > tree, then please email the backport, including the original git commit
> > id to <stable@vger.kernel.org>.
> 
> It's a clean cherry-pick, as git detects the rename of
> poly1305-armv8.pl.  So there should be no need to require this to be
> resent.  Also, missing Cc to linux-crypto.
> 
> Same for 6.12, 6.6, 6.1, 5.15, and 5.10.

As I've said before, the reason this keeps happening is that Greg's
stable scripts perform a cherry-pick by first formatting the commit as a
patch file with the default 3 lines of context, then applying it with
'patch' using the default fuzz of 2.

(The second step seems to occur in the 'apply_it' script, which isn't
public.  But based on the observed behavior, it must be what it does.)

This process is buggy compared to simply using 'git cherry-pick':

- It has no rename detection.  Any file rename, like what happened for
  this commit where poly1305-armv8.pl is in different locations in
  different branches, results in FAILED.  This happens regularly.

- Incorrect backports due to only *one* line of context being
  considered (since 3 - 2 = 1).  For examples of this, see
  https://lore.kernel.org/all/20260512173933.811124271@linuxfoundation.org/
  and
  https://lore.kernel.org/all/20260515154719.961677988@linuxfoundation.org/

  This is easily reproducible.  For example for the first one:

  git checkout -d v6.12.87
  git cherry-pick 2909f0d4994fb4306bf116df5ccee797791fce2c
  git show # correct backport

  git checkout -d v6.12.87
  git format-patch -1 --no-base 2909f0d4994fb4306bf116df5ccee797791fce2c
  patch -p1 < 0001-usb-typec-tcpm-reset-internal-port-states-on-soft-re.patch
  git diff # incorrect backport that was actually sent out

  The second example is even worse, as there the incorrect backport was
  actually released.

Just using 'git cherry-pick', as contributors are already being asked to
do in the FAILED emails themselves, avoids these problems.

Can this please be fixed?  This outdated cherry-pick process is reducing
the quality of the stable releases.

- Eric