Re: [PATCH 5/8] Keep read and write fds with each nlm_file

Bruce Fields
2021-08-23T20:44:03Z

Subject: [PATCH v4] Keep read and write fds with each nlm_file

We shouldn't really be using a read-only file descriptor to take a write
lock.

Most filesystems will put up with it. But NFS, for example, won't.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
---
fs/lockd/svc4proc.c | 4 +-
fs/lockd/svclock.c | 25 ++++++---
fs/lockd/svcproc.c | 4 +-
fs/lockd/svcsubs.c | 102 +++++++++++++++++++++++++-----------
fs/nfsd/lockd.c | 8 ++-
include/linux/lockd/bind.h | 3 +-
include/linux/lockd/lockd.h | 9 +++-
7 files changed, 111 insertions(+), 44 deletions(-)

diff --git a/fs/lockd/svc4proc.c b/fs/lockd/svc4proc.c
index bc496bbd696b..e10ae2c41279 100644
--- a/fs/lockd/svc4proc.c
+++ b/fs/lockd/svc4proc.c
@@ -40,13 +40,15 @@ nlm4svc_retrieve_args(struct svc_rqst *rqstp, struct nlm_args *argp,

/* Obtain file pointer. Not used by FREE_ALL call. */
if (filp != NULL) {
+ int mode = lock_to_openmode(&lock->fl);
+
error = nlm_lookup_file(rqstp, &file, lock);
if (error)
goto no_locks;
*filp = file;

/* Set up the missing parts of the file_lock structure */
- lock->fl.fl_file = file->f_file;
+ lock->fl.fl_file = file->f_file[mode];
lock->fl.fl_pid = current->tgid;
lock->fl.fl_lmops = &nlmsvc_lock_operations;
nlmsvc_locks_init_private(&lock->fl, host, (pid_t)lock->svid);
diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
index bc1cf31f3cce..6abbc92b88e3 100644
--- a/fs/lockd/svclock.c
+++ b/fs/lockd/svclock.c
@@ -471,6 +471,7 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
{
struct nlm_block *block = NULL;
int error;
+ int mode;
__be32 ret;

dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
@@ -524,7 +525,8 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,

if (!wait)
lock->fl.fl_flags &= ~FL_SLEEP;
- error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
+ mode = lock_to_openmode(&lock->fl);
+ error = vfs_lock_file(file->f_file[mode], F_SETLK, &lock->fl, NULL);
lock->fl.fl_flags &= ~FL_SLEEP;

dprintk("lockd: vfs_lock_file returned %d\n", error);
@@ -577,6 +579,7 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
struct nlm_lock *conflock, struct nlm_cookie *cookie)
{
int error;
+ int mode;
__be32 ret;
struct nlm_lockowner *test_owner;

@@ -595,7 +598,8 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
/* If there's a conflicting lock, remember to clean up the test lock */
test_owner = (struct nlm_lockowner *)lock->fl.fl_owner;

- error = vfs_test_lock(file->f_file, &lock->fl);
+ mode = lock_to_openmode(&lock->fl);
+ error = vfs_test_lock(file->f_file[mode], &lock->fl);
if (error) {
/* We can't currently deal with deferred test requests */
if (error == FILE_LOCK_DEFERRED)
@@ -641,7 +645,7 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
__be32
nlmsvc_unlock(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
{
- int error;
+ int error = 0;

dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
nlmsvc_file_inode(file)->i_sb->s_id,
@@ -654,7 +658,12 @@ nlmsvc_unlock(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
nlmsvc_cancel_blocked(net, file, lock);

lock->fl.fl_type = F_UNLCK;
- error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
+ if (file->f_file[O_RDONLY])
+ error = vfs_lock_file(file->f_file[O_RDONLY], F_SETLK,
+ &lock->fl, NULL);
+ if (file->f_file[O_WRONLY])
+ error = vfs_lock_file(file->f_file[O_WRONLY], F_SETLK,
+ &lock->fl, NULL);

return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
}
@@ -671,6 +680,7 @@ nlmsvc_cancel_blocked(struct net *net, struct nlm_file *file, struct nlm_lock *l
{
struct nlm_block *block;
int status = 0;
+ int mode;

dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
nlmsvc_file_inode(file)->i_sb->s_id,
@@ -686,7 +696,8 @@ nlmsvc_cancel_blocked(struct net *net, struct nlm_file *file, struct nlm_lock *l
block = nlmsvc_lookup_block(file, lock);
mutex_unlock(&file->f_mutex);
if (block != NULL) {
- vfs_cancel_lock(block->b_file->f_file,
+ mode = lock_to_openmode(&lock->fl);
+ vfs_cancel_lock(block->b_file->f_file[mode],
&block->b_call->a_args.lock.fl);
status = nlmsvc_unlink_block(block);
nlmsvc_release_block(block);
@@ -803,6 +814,7 @@ nlmsvc_grant_blocked(struct nlm_block *block)
{
struct nlm_file *file = block->b_file;
struct nlm_lock *lock = &block->b_call->a_args.lock;
+ int mode;
int error;
loff_t fl_start, fl_end;

@@ -828,7 +840,8 @@ nlmsvc_grant_blocked(struct nlm_block *block)
lock->fl.fl_flags |= FL_SLEEP;
fl_start = lock->fl.fl_start;
fl_end = lock->fl.fl_end;
- error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
+ mode = lock_to_openmode(&lock->fl);
+ error = vfs_lock_file(file->f_file[mode], F_SETLK, &lock->fl, NULL);
lock->fl.fl_flags &= ~FL_SLEEP;
lock->fl.fl_start = fl_start;
lock->fl.fl_end = fl_end;
diff --git a/fs/lockd/svcproc.c b/fs/lockd/svcproc.c
index f4e5e0eb30fd..99696d3f6dd6 100644
--- a/fs/lockd/svcproc.c
+++ b/fs/lockd/svcproc.c
@@ -55,6 +55,7 @@ nlmsvc_retrieve_args(struct svc_rqst *rqstp, struct nlm_args *argp,
struct nlm_host *host = NULL;
struct nlm_file *file = NULL;
struct nlm_lock *lock = &argp->lock;
+ int mode;
__be32 error = 0;

/* nfsd callbacks must have been installed for this procedure */
@@ -75,7 +76,8 @@ nlmsvc_retrieve_args(struct svc_rqst *rqstp, struct nlm_args *argp,
*filp = file;

/* Set up the missing parts of the file_lock structure */
- lock->fl.fl_file = file->f_file;
+ mode = lock_to_openmode(&lock->fl);
+ lock->fl.fl_file = file->f_file[mode];
lock->fl.fl_pid = current->tgid;
lock->fl.fl_lmops = &nlmsvc_lock_operations;
nlmsvc_locks_init_private(&lock->fl, host, (pid_t)lock->svid);
diff --git a/fs/lockd/svcsubs.c b/fs/lockd/svcsubs.c
index 13e6ffc219ec..cb3a7512c33e 100644
--- a/fs/lockd/svcsubs.c
+++ b/fs/lockd/svcsubs.c
@@ -71,14 +71,35 @@ static inline unsigned int file_hash(struct nfs_fh *f)
return tmp & (FILE_NRHASH - 1);
}

+int lock_to_openmode(struct file_lock *lock)
+{
+ return (lock->fl_type == F_WRLCK) ? O_WRONLY : O_RDONLY;
+}
+
+/*
+ * Open the file. Note that if we're reexporting, for example,
+ * this could block the lockd thread for a while.
+ *
+ * We have to make sure we have the right credential to open
+ * the file.
+ */
+static __be32 nlm_do_fopen(struct svc_rqst *rqstp,
+ struct nlm_file *file, int mode)
+{
+ struct file **fp = &file->f_file[mode];
+ __be32 nfserr;
+
+ if (*fp)
+ return 0;
+ nfserr = nlmsvc_ops->fopen(rqstp, &file->f_handle, fp, mode);
+ if (nfserr)
+ dprintk("lockd: open failed (error %d)\n", nfserr);
+ return nfserr;
+}
+
/*
* Lookup file info. If it doesn't exist, create a file info struct
* and open a (VFS) file for the given inode.
- *
- * FIXME:
- * Note that we open the file O_RDONLY even when creating write locks.
- * This is not quite right, but for now, we assume the client performs
- * the proper R/W checking.
*/
__be32
nlm_lookup_file(struct svc_rqst *rqstp, struct nlm_file **result,
@@ -87,42 +108,38 @@ nlm_lookup_file(struct svc_rqst *rqstp, struct nlm_file **result,
struct nlm_file *file;
unsigned int hash;
__be32 nfserr;
+ int mode;

nlm_debug_print_fh("nlm_lookup_file", &lock->fh);

hash = file_hash(&lock->fh);
+ mode = lock_to_openmode(&lock->fl);

/* Lock file table */
mutex_lock(&nlm_file_mutex);

hlist_for_each_entry(file, &nlm_files[hash], f_list)
- if (!nfs_compare_fh(&file->f_handle, &lock->fh))
+ if (!nfs_compare_fh(&file->f_handle, &lock->fh)) {
+ mutex_lock(&file->f_mutex);
+ nfserr = nlm_do_fopen(rqstp, file, mode);
+ mutex_unlock(&file->f_mutex);
goto found;
-
+ }
nlm_debug_print_fh("creating file for", &lock->fh);

nfserr = nlm_lck_denied_nolocks;
file = kzalloc(sizeof(*file), GFP_KERNEL);
if (!file)
- goto out_unlock;
+ goto out_free;

memcpy(&file->f_handle, &lock->fh, sizeof(struct nfs_fh));
mutex_init(&file->f_mutex);
INIT_HLIST_NODE(&file->f_list);
INIT_LIST_HEAD(&file->f_blocks);

- /*
- * Open the file. Note that if we're reexporting, for example,
- * this could block the lockd thread for a while.
- *
- * We have to make sure we have the right credential to open
- * the file.
- */
- nfserr = nlmsvc_ops->fopen(rqstp, &lock->fh, &file->f_file);
- if (nfserr) {
- dprintk("lockd: open failed (error %d)\n", nfserr);
- goto out_free;
- }
+ nfserr = nlm_do_fopen(rqstp, file, mode);
+ if (nfserr)
+ goto out_unlock;

hlist_add_head(&file->f_list, &nlm_files[hash]);

@@ -130,7 +147,6 @@ nlm_lookup_file(struct svc_rqst *rqstp, struct nlm_file **result,
dprintk("lockd: found file %p (count %d)\n", file, file->f_count);
*result = file;
file->f_count++;
- nfserr = 0;

out_unlock:
mutex_unlock(&nlm_file_mutex);
@@ -150,13 +166,34 @@ nlm_delete_file(struct nlm_file *file)
nlm_debug_print_file("closing file", file);
if (!hlist_unhashed(&file->f_list)) {
hlist_del(&file->f_list);
- nlmsvc_ops->fclose(file->f_file);
+ if (file->f_file[O_RDONLY])
+ nlmsvc_ops->fclose(file->f_file[O_RDONLY]);
+ if (file->f_file[O_WRONLY])
+ nlmsvc_ops->fclose(file->f_file[O_WRONLY]);
kfree(file);
} else {
printk(KERN_WARNING "lockd: attempt to release unknown file!\n");
}
}

+static int nlm_unlock_files(struct nlm_file *file)
+{
+ struct file_lock lock;
+ struct file *f;
+
+ lock.fl_type = F_UNLCK;
+ lock.fl_start = 0;
+ lock.fl_end = OFFSET_MAX;
+ for (f = file->f_file[0]; f <= file->f_file[1]; f++) {
+ if (f && vfs_lock_file(f, F_SETLK, &lock, NULL) < 0) {
+ pr_warn("lockd: unlock failure in %s:%d\n",
+ __FILE__, __LINE__);
+ return 1;
+ }
+ }
+ return 0;
+}
+
/*
* Loop over all locks on the given file and perform the specified
* action.
@@ -184,17 +221,10 @@ nlm_traverse_locks(struct nlm_host *host, struct nlm_file *file,

lockhost = ((struct nlm_lockowner *)fl->fl_owner)->host;
if (match(lockhost, host)) {
- struct file_lock lock = *fl;

spin_unlock(&flctx->flc_lock);
- lock.fl_type = F_UNLCK;
- lock.fl_start = 0;
- lock.fl_end = OFFSET_MAX;
- if (vfs_lock_file(file->f_file, F_SETLK, &lock, NULL) < 0) {
- printk("lockd: unlock failure in %s:%d\n",
- __FILE__, __LINE__);
+ if (nlm_unlock_files(file))
return 1;
- }
goto again;
}
}
@@ -248,6 +278,15 @@ nlm_file_inuse(struct nlm_file *file)
return 0;
}

+static void nlm_close_files(struct nlm_file *file)
+{
+ struct file *f;
+
+ for (f = file->f_file[0]; f <= file->f_file[1]; f++)
+ if (f)
+ nlmsvc_ops->fclose(f);
+}
+
/*
* Loop over all files in the file table.
*/
@@ -278,7 +317,7 @@ nlm_traverse_files(void *data, nlm_host_match_fn_t match,
if (list_empty(&file->f_blocks) && !file->f_locks
&& !file->f_shares && !file->f_count) {
hlist_del(&file->f_list);
- nlmsvc_ops->fclose(file->f_file);
+ nlm_close_files(file);
kfree(file);
}
}
@@ -412,6 +451,7 @@ nlmsvc_invalidate_all(void)
nlm_traverse_files(NULL, nlmsvc_is_client, NULL);
}

+
static int
nlmsvc_match_sb(void *datap, struct nlm_file *file)
{
diff --git a/fs/nfsd/lockd.c b/fs/nfsd/lockd.c
index 3f5b3d7b62b7..606fa155c28a 100644
--- a/fs/nfsd/lockd.c
+++ b/fs/nfsd/lockd.c
@@ -25,9 +25,11 @@
* Note: we hold the dentry use count while the file is open.
*/
static __be32
-nlm_fopen(struct svc_rqst *rqstp, struct nfs_fh *f, struct file **filp)
+nlm_fopen(struct svc_rqst *rqstp, struct nfs_fh *f, struct file **filp,
+ int mode)
{
__be32 nfserr;
+ int access;
struct svc_fh fh;

/* must initialize before using! but maxsize doesn't matter */
@@ -36,7 +38,9 @@ nlm_fopen(struct svc_rqst *rqstp, struct nfs_fh *f, struct file **filp)
memcpy((char*)&fh.fh_handle.fh_base, f->data, f->size);
fh.fh_export = NULL;

- nfserr = nfsd_open(rqstp, &fh, S_IFREG, NFSD_MAY_LOCK, filp);
+ access = (mode == O_WRONLY) ? NFSD_MAY_WRITE : NFSD_MAY_READ;
+ access |= NFSD_MAY_LOCK;
+ nfserr = nfsd_open(rqstp, &fh, S_IFREG, access, filp);
fh_put(&fh);
/* We return nlm error codes as nlm doesn't know
* about nfsd, but nfsd does know about nlm..
diff --git a/include/linux/lockd/bind.h b/include/linux/lockd/bind.h
index 0520c0cd73f4..3bc9f7410e21 100644
--- a/include/linux/lockd/bind.h
+++ b/include/linux/lockd/bind.h
@@ -27,7 +27,8 @@ struct rpc_task;
struct nlmsvc_binding {
__be32 (*fopen)(struct svc_rqst *,
struct nfs_fh *,
- struct file **);
+ struct file **,
+ int mode);
void (*fclose)(struct file *);
};

diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/lockd.h
index 81b71ad2040a..da319de7e557 100644
--- a/include/linux/lockd/lockd.h
+++ b/include/linux/lockd/lockd.h
@@ -10,6 +10,8 @@
#ifndef LINUX_LOCKD_LOCKD_H
#define LINUX_LOCKD_LOCKD_H

+/* XXX: a lot of this should really be under fs/lockd. */
+
#include <linux/in.h>
#include <linux/in6.h>
#include <net/ipv6.h>
@@ -154,7 +156,8 @@ struct nlm_rqst {
struct nlm_file {
struct hlist_node f_list; /* linked list */
struct nfs_fh f_handle; /* NFS file handle */
- struct file * f_file; /* VFS file pointer */
+ struct file * f_file[2]; /* VFS file pointers,
+ indexed by O_ flags */
struct nlm_share * f_shares; /* DOS shares */
struct list_head f_blocks; /* blocked locks */
unsigned int f_locks; /* guesstimate # of locks */
@@ -267,6 +270,7 @@ typedef int (*nlm_host_match_fn_t)(void *cur, struct nlm_host *ref);
/*
* Server-side lock handling
*/
+int lock_to_openmode(struct file_lock *);
__be32 nlmsvc_lock(struct svc_rqst *, struct nlm_file *,
struct nlm_host *, struct nlm_lock *, int,
struct nlm_cookie *, int);
@@ -301,7 +305,8 @@ int nlmsvc_unlock_all_by_ip(struct sockaddr *server_addr);

static inline struct inode *nlmsvc_file_inode(struct nlm_file *file)
{
- return locks_inode(file->f_file);
+ return locks_inode(file->f_file[0] ?
+ file->f_file[0] : file->f_file[1]);
}

static inline int __nlm_privileged_request4(const struct sockaddr *sap)
--
2.31.1