Re: [PATCH 6.6.y] smb: client: support kvec iterators in async read path

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, Nov 21, 2025 at 02:31:20AM -0800, Bharath SM wrote:
> On Fri, Nov 21, 2025 at 2:02 AM Greg KH <gregkh@linuxfoundation.org> wrote:
> >
> > On Thu, Nov 06, 2025 at 06:02:39AM -0800, Bharath SM wrote:
> > > On Fri, Jul 11, 2025 at 9:01 AM Henrique Carvalho
> > > <henrique.carvalho@suse.com> wrote:
> > > >
> > > > On Fri, Jul 11, 2025 at 10:01:58AM +0100, David Howells wrote:
> > > > > Henrique Carvalho <henrique.carvalho@suse.com> wrote:
> > > > >
> > > > > > Add cifs_limit_kvec_subset() and select the appropriate limiter in
> > > > > > cifs_send_async_read() to handle kvec iterators in async read path,
> > > > > > fixing the EIO bug when running executables in cifs shares mounted
> > > > > > with nolease.
> > > > > >
> > > > > > This patch -- or equivalent patch, does not exist upstream, as the
> > > > > > upstream code has suffered considerable API changes. The affected path
> > > > > > is currently handled by netfs lib and located under netfs/direct_read.c.
> > > > >
> > > > > Are you saying that you do see this upstream too?
> > > > >
> > > >
> > > > No, the patch only targets the 6.6.y stable tree. Since version 6.8,
> > > > this path has moved into the netfs layer, so the original bug no longer
> > > > exists.
> > > >
> > > > The bug was fixed at least since the commit referred in the commit
> > > > message -- 3ee1a1fc3981. In this commit, the call to cifs_user_readv()
> > > > is replaced by a call to netfs_unbuffered_read_iter(), inside the
> > > > function cifs_strict_readv().
> > > >
> > > > netfs_unbuffered_read_iter() itself was introduced in commit
> > > > 016dc8516aec8, along with other netfs api changes, present in kernel
> > > > versions 6.8+.
> > > >
> > > > Backporting netfs directly would be non-trivial. Instead, I:
> > > >
> > > > - add cifs_limit_kvec_subset(), modeled on the existing
> > > >   cifs_limit_bvec_subset()
> > > > - choose between the kvec or bvec limiter function early in
> > > >   cifs_write_from_iter().
> > > >
> > > > The Fixes tag references d08089f649a0c, which implements
> > > > cifs_limit_bvec_subset() and uses it inside cifs_write_from_iter().
> > > >
> > > > > > Reproducer:
> > > > > >
> > > > > > $ mount.cifs //server/share /mnt -o nolease
> > > > > > $ cat - > /mnt/test.sh <<EOL
> > > > > > echo hallo
> > > > > > EOL
> > > > > > $ chmod +x /mnt/test.sh
> > > > > > $ /mnt/test.sh
> > > > > > bash: /mnt/test.sh: /bin/bash: Defekter Interpreter: Eingabe-/Ausgabefehler
> > > > > > $ rm -f /mnt/test.sh
> > > > >
> > > > > Is this what you are expecting to see when it works or when it fails?
> > > > >
> > > >
> > > > This is the reproducer for the observed bug. In english it reads "Bad
> > > > interpreter: Input/Output error".
> > > >
> > > > FYI: I tried to follow Option 3 of the stable-kernel rules for submission:
> > > > <https://www.kernel.org/doc/html/v6.15/process/stable-kernel-rules.html>
> > > > Please let me know if you'd prefer a different approach or any further
> > > > changes.
> > > Thanks Henrique.
> > >
> > > Hi Greg,
> > >
> > > We are observing the same issue with the 6.6 Kernel, Can you please
> > > help include this patch in the 6.6 stable kernel.?
> >
> > Pleas provide a working backport and we will be glad to imclude it.
> >
> This fix is not needed now in the stable kernels as "[PATCH] cifs: Fix
> uncached read into ITER_KVEC iterator" submitted
> in email thread "Request to backport data corruption fix to stable"
> fixes this issue.

I do not understand, what commit fixed this?  You attached a fix, but
that's not needed?

confused,

greg k-h