linux-kernel - Re: [PATCH] nfsd: make a copy of struct iattr before calling notify

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Date:   Fri, 19 May 2023 06:10:01 -0400
From:   Jeff Layton <jlayton@...nel.org>
To:     Chuck Lever <chuck.lever@...cle.com>
Cc:     Zhi Li <yieli@...hat.com>, linux-nfs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nfsd: make a copy of struct iattr before calling
 notify_change

On Wed, 2023-05-17 at 12:26 -0400, Jeff Layton wrote:
> notify_change can modify the iattr structure. In particular it can can
> end up setting ATTR_MODE when ATTR_KILL_SUID is already set, causing a
> BUG() if the same iattr is passed to notify_change more than once.
> 
> Make a copy of the struct iattr before calling notify_change.
> 
> Fixes: 34b91dda7124 NFSD: Make nfsd4_setattr() wait before returning NFS4ERR_DELAY
> Link: https://bugzilla.redhat.com/show_bug.cgi?id=2207969
> Reported-by: Zhi Li <yieli@...hat.com>
> Signed-off-by: Jeff Layton <jlayton@...nel.org>
> ---
>  fs/nfsd/vfs.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index c4ef24c5ffd0..ad0c5cd900b1 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -538,7 +538,9 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp,
>  
>  	inode_lock(inode);
>  	for (retries = 1;;) {
> -		host_err = __nfsd_setattr(dentry, iap);
> +		struct iattr attrs = *iap;
> +
> +		host_err = __nfsd_setattr(dentry, &attrs);
>  		if (host_err != -EAGAIN || !retries--)
>  			break;
>  		if (!nfsd_wait_for_delegreturn(rqstp, inode))

Zhi Li tested the test kernel for this today and this seems to have
fixed the issue. I think you can add:

Tested-by: Zhi Li <yieli@...hat.com>

Cheers,
Jeff