Re: [PATCH] nfsd: fix leaked file lock with nfs exported overlayfs

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On Fri, 2018-07-13 at 17:22 +0300, Amir Goldstein wrote:
> nfsd and lockd call vfs_lock_file() to lock/unlock the inode
> returned by locks_inode(file).
> 
> Many places in nfsd/lockd code use the inode returned by
> file_inode(file) for lock manipulation. With Overlayfs, file_inode()
> (the underlying inode) is not the same object as locks_inode() (the
> overlay inode). This can result in "Leaked POSIX lock" messages
> and eventually to a kernel crash as reported by Eddie Horng:
> https://marc.info/?l=linux-unionfs&m=153086643202072&w=2
> 
> Fix all the call sites in nfsd/lockd that should use locks_inode().
> This is a correctness bug that manifested when overlayfs gained
> NFS export support in v4.16.
> 
> Reported-by: Eddie Horng <eddiehorng.tw@xxxxxxxxx>
> Tested-by: Eddie Horng <eddiehorng.tw@xxxxxxxxx>
> Cc: Jeff Layton <jlayton@xxxxxxxxxx>
> Fixes: 8383f1748829 ("ovl: wire up NFS export operations")
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> 
> Hi Bruce,
> 
> For the purpose of locks, nfsd/lockd should look at locks_inode()
> just like vfs lock functions.
> 
> Hopefully, Miklos's work on stacked overlayfs file operations will
> be merged soon and locks_inode() will become the same as file_inode(),
> but we will still need this fix for stable kernels v4.16 through v4.18.
> 
> Beyond testing by Eddie, I also verified no regressions when running
> nfstest with exported overlayfs.
> 
> Thanks,
> Amir.
> 
>  fs/lockd/clntlock.c         |  2 +-
>  fs/lockd/clntproc.c         |  2 +-
>  fs/lockd/svclock.c          | 16 ++++++++--------
>  fs/lockd/svcsubs.c          |  4 ++--
>  fs/nfsd/nfs4state.c         |  2 +-
>  include/linux/lockd/lockd.h |  4 ++--
>  6 files changed, 15 insertions(+), 15 deletions(-)
> 
> diff --git a/fs/lockd/clntlock.c b/fs/lockd/clntlock.c
> index 96c1d14c18f1..c2a128678e6e 100644
> --- a/fs/lockd/clntlock.c
> +++ b/fs/lockd/clntlock.c
> @@ -187,7 +187,7 @@ __be32 nlmclnt_grant(const struct sockaddr *addr, const struct nlm_lock *lock)
>  			continue;
>  		if (!rpc_cmp_addr(nlm_addr(block->b_host), addr))
>  			continue;
> -		if (nfs_compare_fh(NFS_FH(file_inode(fl_blocked->fl_file)) ,fh) != 0)
> +		if (nfs_compare_fh(NFS_FH(locks_inode(fl_blocked->fl_file)), fh) != 0)
>  			continue;
>  		/* Alright, we found a lock. Set the return status
>  		 * and wake up the caller
> diff --git a/fs/lockd/clntproc.c b/fs/lockd/clntproc.c
> index a2c0dfc6fdc0..d20b92f271c2 100644
> --- a/fs/lockd/clntproc.c
> +++ b/fs/lockd/clntproc.c
> @@ -128,7 +128,7 @@ static void nlmclnt_setlockargs(struct nlm_rqst *req, struct file_lock *fl)
>  	char *nodename = req->a_host->h_rpcclnt->cl_nodename;
>  
>  	nlmclnt_next_cookie(&argp->cookie);
> -	memcpy(&lock->fh, NFS_FH(file_inode(fl->fl_file)), sizeof(struct nfs_fh));
> +	memcpy(&lock->fh, NFS_FH(locks_inode(fl->fl_file)), sizeof(struct nfs_fh));
>  	lock->caller  = nodename;
>  	lock->oh.data = req->a_owner;
>  	lock->oh.len  = snprintf(req->a_owner, sizeof(req->a_owner), "%u@%s",
> diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
> index 3701bccab478..74330daeab71 100644
> --- a/fs/lockd/svclock.c
> +++ b/fs/lockd/svclock.c
> @@ -405,8 +405,8 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
>  	__be32			ret;
>  
>  	dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
> -				file_inode(file->f_file)->i_sb->s_id,
> -				file_inode(file->f_file)->i_ino,
> +				locks_inode(file->f_file)->i_sb->s_id,
> +				locks_inode(file->f_file)->i_ino,
>  				lock->fl.fl_type, lock->fl.fl_pid,
>  				(long long)lock->fl.fl_start,
>  				(long long)lock->fl.fl_end,
> @@ -511,8 +511,8 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
>  	__be32			ret;
>  
>  	dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
> -				file_inode(file->f_file)->i_sb->s_id,
> -				file_inode(file->f_file)->i_ino,
> +				locks_inode(file->f_file)->i_sb->s_id,
> +				locks_inode(file->f_file)->i_ino,
>  				lock->fl.fl_type,
>  				(long long)lock->fl.fl_start,
>  				(long long)lock->fl.fl_end);
> @@ -566,8 +566,8 @@ nlmsvc_unlock(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
>  	int	error;
>  
>  	dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
> -				file_inode(file->f_file)->i_sb->s_id,
> -				file_inode(file->f_file)->i_ino,
> +				locks_inode(file->f_file)->i_sb->s_id,
> +				locks_inode(file->f_file)->i_ino,
>  				lock->fl.fl_pid,
>  				(long long)lock->fl.fl_start,
>  				(long long)lock->fl.fl_end);
> @@ -595,8 +595,8 @@ nlmsvc_cancel_blocked(struct net *net, struct nlm_file *file, struct nlm_lock *l
>  	int status = 0;
>  
>  	dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
> -				file_inode(file->f_file)->i_sb->s_id,
> -				file_inode(file->f_file)->i_ino,
> +				locks_inode(file->f_file)->i_sb->s_id,
> +				locks_inode(file->f_file)->i_ino,
>  				lock->fl.fl_pid,
>  				(long long)lock->fl.fl_start,
>  				(long long)lock->fl.fl_end);
> diff --git a/fs/lockd/svcsubs.c b/fs/lockd/svcsubs.c
> index 4ec3d6e03e76..899360ba3b84 100644
> --- a/fs/lockd/svcsubs.c
> +++ b/fs/lockd/svcsubs.c
> @@ -44,7 +44,7 @@ static inline void nlm_debug_print_fh(char *msg, struct nfs_fh *f)
>  
>  static inline void nlm_debug_print_file(char *msg, struct nlm_file *file)
>  {
> -	struct inode *inode = file_inode(file->f_file);
> +	struct inode *inode = locks_inode(file->f_file);
>  
>  	dprintk("lockd: %s %s/%ld\n",
>  		msg, inode->i_sb->s_id, inode->i_ino);
> @@ -414,7 +414,7 @@ nlmsvc_match_sb(void *datap, struct nlm_file *file)
>  {
>  	struct super_block *sb = datap;
>  
> -	return sb == file_inode(file->f_file)->i_sb;
> +	return sb == locks_inode(file->f_file)->i_sb;
>  }
>  
>  /**
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 857141446d6b..4a17fad93411 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -6293,7 +6293,7 @@ check_for_locks(struct nfs4_file *fp, struct nfs4_lockowner *lowner)
>  		return status;
>  	}
>  
> -	inode = file_inode(filp);
> +	inode = locks_inode(filp);
>  	flctx = inode->i_flctx;
>  
>  	if (flctx && !list_empty_careful(&flctx->flc_posix)) {
> diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/lockd.h
> index 4fd95dbeb52f..b065ef406770 100644
> --- a/include/linux/lockd/lockd.h
> +++ b/include/linux/lockd/lockd.h
> @@ -299,7 +299,7 @@ int           nlmsvc_unlock_all_by_ip(struct sockaddr *server_addr);
>  
>  static inline struct inode *nlmsvc_file_inode(struct nlm_file *file)
>  {
> -	return file_inode(file->f_file);
> +	return locks_inode(file->f_file);
>  }
>  

fwiw, I think the above delta turns out to be the real fix here, as that
affects nlm_file_inuse.
 
>  static inline int __nlm_privileged_request4(const struct sockaddr *sap)
> @@ -359,7 +359,7 @@ static inline int nlm_privileged_requester(const struct svc_rqst *rqstp)
>  static inline int nlm_compare_locks(const struct file_lock *fl1,
>  				    const struct file_lock *fl2)
>  {
> -	return file_inode(fl1->fl_file) == file_inode(fl2->fl_file)
> +	return locks_inode(fl1->fl_file) == locks_inode(fl2->fl_file)
>  	     && fl1->fl_pid   == fl2->fl_pid
>  	     && fl1->fl_owner == fl2->fl_owner
>  	     && fl1->fl_start == fl2->fl_start

I think this looks OK. I was a bit hesitant as I wasn't sure whether
this would change the filehandles presented by the nfsd, but I don't
think it will.

Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
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