> On Jun 13, 2022, at 9:40 AM, Benjamin Coddington <bcodding@xxxxxxxxxx> wrote:
>
> Instead of trusting that struct file_lock returns completely unchanged
> after vfs_test_lock() when there's no conflicting lock, stash away our
> nlm_lockowner reference so we can properly release it for all cases.
>
> This defends against another file_lock implementation overwriting fl_owner
> when the return type is F_UNLCK.
>
> Reported-by: Roberto Bergantinos Corpas <rbergant@xxxxxxxxxx>
> Tested-by: Roberto Bergantinos Corpas <rbergant@xxxxxxxxxx>
> Signed-off-by: Benjamin Coddington <bcodding@xxxxxxxxxx>
LGTM. Applied internally for more testing. Comment period
still open.
> ---
> fs/lockd/svc4proc.c | 4 +++-
> fs/lockd/svclock.c | 10 +---------
> fs/lockd/svcproc.c | 5 ++++-
> include/linux/lockd/lockd.h | 1 +
> 4 files changed, 9 insertions(+), 11 deletions(-)
>
> diff --git a/fs/lockd/svc4proc.c b/fs/lockd/svc4proc.c
> index 176b468a61c7..4f247ab8be61 100644
> --- a/fs/lockd/svc4proc.c
> +++ b/fs/lockd/svc4proc.c
> @@ -87,6 +87,7 @@ __nlm4svc_proc_test(struct svc_rqst *rqstp, struct nlm_res *resp)
> struct nlm_args *argp = rqstp->rq_argp;
> struct nlm_host *host;
> struct nlm_file *file;
> + struct nlm_lockowner *test_owner;
> __be32 rc = rpc_success;
>
> dprintk("lockd: TEST4 called\n");
> @@ -96,6 +97,7 @@ __nlm4svc_proc_test(struct svc_rqst *rqstp, struct nlm_res *resp)
> if ((resp->status = nlm4svc_retrieve_args(rqstp, argp, &host, &file)))
> return resp->status == nlm_drop_reply ? rpc_drop_reply :rpc_success;
>
> + test_owner = argp->lock.fl.fl_owner;
> /* Now check for conflicting locks */
> resp->status = nlmsvc_testlock(rqstp, file, host, &argp->lock, &resp->lock, &resp->cookie);
> if (resp->status == nlm_drop_reply)
> @@ -103,7 +105,7 @@ __nlm4svc_proc_test(struct svc_rqst *rqstp, struct nlm_res *resp)
> else
> dprintk("lockd: TEST4 status %d\n", ntohl(resp->status));
>
> - nlmsvc_release_lockowner(&argp->lock);
> + nlmsvc_put_lockowner(test_owner);
> nlmsvc_release_host(host);
> nlm_release_file(file);
> return rc;
> diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
> index cb3658ab9b7a..9c1aa75441e1 100644
> --- a/fs/lockd/svclock.c
> +++ b/fs/lockd/svclock.c
> @@ -340,7 +340,7 @@ nlmsvc_get_lockowner(struct nlm_lockowner *lockowner)
> return lockowner;
> }
>
> -static void nlmsvc_put_lockowner(struct nlm_lockowner *lockowner)
> +void nlmsvc_put_lockowner(struct nlm_lockowner *lockowner)
> {
> if (!refcount_dec_and_lock(&lockowner->count, &lockowner->host->h_lock))
> return;
> @@ -590,7 +590,6 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
> int error;
> int mode;
> __be32 ret;
> - struct nlm_lockowner *test_owner;
>
> dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
> nlmsvc_file_inode(file)->i_sb->s_id,
> @@ -604,9 +603,6 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
> goto out;
> }
>
> - /* If there's a conflicting lock, remember to clean up the test lock */
> - test_owner = (struct nlm_lockowner *)lock->fl.fl_owner;
> -
> mode = lock_to_openmode(&lock->fl);
> error = vfs_test_lock(file->f_file[mode], &lock->fl);
> if (error) {
> @@ -635,10 +631,6 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
> conflock->fl.fl_end = lock->fl.fl_end;
> locks_release_private(&lock->fl);
>
> - /* Clean up the test lock */
> - lock->fl.fl_owner = NULL;
> - nlmsvc_put_lockowner(test_owner);
> -
> ret = nlm_lck_denied;
> out:
> return ret;
> diff --git a/fs/lockd/svcproc.c b/fs/lockd/svcproc.c
> index 4dc1b40a489a..b09ca35b527c 100644
> --- a/fs/lockd/svcproc.c
> +++ b/fs/lockd/svcproc.c
> @@ -116,6 +116,7 @@ __nlmsvc_proc_test(struct svc_rqst *rqstp, struct nlm_res *resp)
> struct nlm_args *argp = rqstp->rq_argp;
> struct nlm_host *host;
> struct nlm_file *file;
> + struct nlm_lockowner *test_owner;
> __be32 rc = rpc_success;
>
> dprintk("lockd: TEST called\n");
> @@ -125,6 +126,8 @@ __nlmsvc_proc_test(struct svc_rqst *rqstp, struct nlm_res *resp)
> if ((resp->status = nlmsvc_retrieve_args(rqstp, argp, &host, &file)))
> return resp->status == nlm_drop_reply ? rpc_drop_reply :rpc_success;
>
> + test_owner = argp->lock.fl.fl_owner;
> +
> /* Now check for conflicting locks */
> resp->status = cast_status(nlmsvc_testlock(rqstp, file, host, &argp->lock, &resp->lock, &resp->cookie));
> if (resp->status == nlm_drop_reply)
> @@ -133,7 +136,7 @@ __nlmsvc_proc_test(struct svc_rqst *rqstp, struct nlm_res *resp)
> dprintk("lockd: TEST status %d vers %d\n",
> ntohl(resp->status), rqstp->rq_vers);
>
> - nlmsvc_release_lockowner(&argp->lock);
> + nlmsvc_put_lockowner(test_owner);
> nlmsvc_release_host(host);
> nlm_release_file(file);
> return rc;
> diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/lockd.h
> index fcef192e5e45..70ce419e2709 100644
> --- a/include/linux/lockd/lockd.h
> +++ b/include/linux/lockd/lockd.h
> @@ -292,6 +292,7 @@ void nlmsvc_locks_init_private(struct file_lock *, struct nlm_host *, pid_t);
> __be32 nlm_lookup_file(struct svc_rqst *, struct nlm_file **,
> struct nlm_lock *);
> void nlm_release_file(struct nlm_file *);
> +void nlmsvc_put_lockowner(struct nlm_lockowner *);
> void nlmsvc_release_lockowner(struct nlm_lock *);
> void nlmsvc_mark_resources(struct net *);
> void nlmsvc_free_host_resources(struct nlm_host *);
> --
> 2.31.1
>
--
Chuck Lever
