CIFS: Do not permit write to a range mandatory locked with a read lock

We don't need to permit a write to the area locked with a read lock
by any process including the process that issues the write.

Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <smfrench@gmail.com>

diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 15a8cb66a07bf7ad3625bf06f32514b0287321ea..a152f3645b09abe7f7fd13dbb106ca27fd2b75f7 100644 (file)
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -186,7 +186,7 @@ extern void cifs_mark_open_files_invalid(struct cifs_tcon *tcon);
 extern bool cifs_find_lock_conflict(struct cifsFileInfo *cfile, __u64 offset,
                                    __u64 length, __u8 type,
                                    struct cifsLockInfo **conf_lock,
-                                   bool rw_check);
+                                   int rw_check);
 extern void cifs_add_pending_open(struct cifs_fid *fid,
                                  struct tcon_link *tlink,
                                  struct cifs_pending_open *open);

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index bceffa8c034eb55dba9d0be7ec53086ea5c2a2a9..ebebbb2bc1fb811eb68aeb6c65d08e23e7e76e90 100644 (file)
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -759,10 +759,15 @@ cifs_del_lock_waiters(struct cifsLockInfo *lock)
        }
 }
 
+#define CIFS_LOCK_OP   0
+#define CIFS_READ_OP   1
+#define CIFS_WRITE_OP  2
+
+/* @rw_check : 0 - no op, 1 - read, 2 - write */
 static bool
 cifs_find_fid_lock_conflict(struct cifs_fid_locks *fdlocks, __u64 offset,
                            __u64 length, __u8 type, struct cifsFileInfo *cfile,
-                           struct cifsLockInfo **conf_lock, bool rw_check)
+                           struct cifsLockInfo **conf_lock, int rw_check)
 {
        struct cifsLockInfo *li;
        struct cifsFileInfo *cur_cfile = fdlocks->cfile;
@@ -772,9 +777,13 @@ cifs_find_fid_lock_conflict(struct cifs_fid_locks *fdlocks, __u64 offset,
                if (offset + length <= li->offset ||
                    offset >= li->offset + li->length)
                        continue;
-               if (rw_check && server->ops->compare_fids(cfile, cur_cfile) &&
-                   current->tgid == li->pid)
-                       continue;
+               if (rw_check != CIFS_LOCK_OP && current->tgid == li->pid &&
+                   server->ops->compare_fids(cfile, cur_cfile)) {
+                       /* shared lock prevents write op through the same fid */
+                       if (!(li->type & server->vals->shared_lock_type) ||
+                           rw_check != CIFS_WRITE_OP)
+                               continue;
+               }
                if ((type & server->vals->shared_lock_type) &&
                    ((server->ops->compare_fids(cfile, cur_cfile) &&
                     current->tgid == li->pid) || type == li->type))
@@ -789,7 +798,7 @@ cifs_find_fid_lock_conflict(struct cifs_fid_locks *fdlocks, __u64 offset,
 bool
 cifs_find_lock_conflict(struct cifsFileInfo *cfile, __u64 offset, __u64 length,
                        __u8 type, struct cifsLockInfo **conf_lock,
-                       bool rw_check)
+                       int rw_check)
 {
        bool rc = false;
        struct cifs_fid_locks *cur;
@@ -825,7 +834,7 @@ cifs_lock_test(struct cifsFileInfo *cfile, __u64 offset, __u64 length,
        down_read(&cinode->lock_sem);
 
        exist = cifs_find_lock_conflict(cfile, offset, length, type,
-                                       &conf_lock, false);
+                                       &conf_lock, CIFS_LOCK_OP);
        if (exist) {
                flock->fl_start = conf_lock->offset;
                flock->fl_end = conf_lock->offset + conf_lock->length - 1;
@@ -872,7 +881,7 @@ try_again:
        down_write(&cinode->lock_sem);
 
        exist = cifs_find_lock_conflict(cfile, lock->offset, lock->length,
-                                       lock->type, &conf_lock, false);
+                                       lock->type, &conf_lock, CIFS_LOCK_OP);
        if (!exist && cinode->can_cache_brlcks) {
                list_add_tail(&lock->llist, &cfile->llist->locks);
                up_write(&cinode->lock_sem);
@@ -2466,7 +2475,7 @@ cifs_writev(struct kiocb *iocb, const struct iovec *iov,
        down_read(&cinode->lock_sem);
        if (!cifs_find_lock_conflict(cfile, pos, iov_length(iov, nr_segs),
                                     server->vals->exclusive_lock_type, NULL,
-                                    true)) {
+                                    CIFS_WRITE_OP)) {
                mutex_lock(&inode->i_mutex);
                rc = __generic_file_aio_write(iocb, iov, nr_segs,
                                               &iocb->ki_pos);
@@ -2901,7 +2910,7 @@ cifs_strict_readv(struct kiocb *iocb, const struct iovec *iov,
        down_read(&cinode->lock_sem);
        if (!cifs_find_lock_conflict(cfile, pos, iov_length(iov, nr_segs),
                                     tcon->ses->server->vals->shared_lock_type,
-                                    NULL, true))
+                                    NULL, CIFS_READ_OP))
                rc = generic_file_aio_read(iocb, iov, nr_segs, pos);
        up_read(&cinode->lock_sem);
        return rc;