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Date:   Sun, 16 Oct 2022 21:17:45 -0700
From:   Kees Cook <>
To:     Bagas Sanjaya <>
Cc:     Dave Jones <>,
        Linux Kernel Mailing List <>,,,
        Trond Myklebust <>,
        Scott Mayhew <>,
        Anna Schumaker <>,
        Linus Torvalds <>
Subject: Re: 6.1rc1: NFS memcpy warning on mount

On Mon, Oct 17, 2022 at 10:58:55AM +0700, Bagas Sanjaya wrote:
> On Sun, Oct 16, 2022 at 10:58:21PM -0400, Dave Jones wrote:
> > Started getting this during mount on a 6.1rc1 kernel..
> > not sure which mount it's complaining about, but they're all v3 tcp
> > mounts on that machine.
> > 
> > [   19.617475] memcpy: detected field-spanning write (size 28) of single field "" at fs/nfs/super.c:857 (size 18446744073709551615)
> [...]
> Hmm, the blamed line in the warning is introduced by 38465f5d1af932 ("NFS:
> rename nfs_fs_context pointer arg in a few functions"). Cc: the commit
> author. Also Cc: Kees for authoring the patch [1] that have fixed
> similar warning.

The warning is from commit 54d9469bc515 ("fortify: Add run-time WARN
for cross-field memcpy()")

> Also, does v6.0 have this warning? If so, you need to bisect in the range
> of v6.0..v6.1-rc1.

No need for bisection -- this is almost certainly a false positive (as
detailed in the above commit: we're working on purging all of these
cases from the kernel).

> [1]:

Yeah, I have a v2 of this patch, which should also fix this
issue. Sending shortly...

Kees Cook

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