cifs: have find_readable/writable_file filter by fsuid

When we implement multiuser mounts, we'll need to filter filehandles
by fsuid. Add a flag for multiuser mounts and code to filter by
fsuid when it's set.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 25 insertions, 8 deletions

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 24332d437150..80856f180711 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -1168,9 +1168,15 @@ static ssize_t cifs_write(struct file *file, const char *write_data,
 }
 
 #ifdef CONFIG_CIFS_EXPERIMENTAL
-struct cifsFileInfo *find_readable_file(struct cifsInodeInfo *cifs_inode)
+struct cifsFileInfo *find_readable_file(struct cifsInodeInfo *cifs_inode,
+                                        bool fsuid_only)
 {
         struct cifsFileInfo *open_file = NULL;
+        struct cifs_sb_info *cifs_sb = CIFS_SB(cifs_inode->vfs_inode.i_sb);
+
+        /* only filter by fsuid on multiuser mounts */
+        if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MULTIUSER))
+                fsuid_only = false;
 
         read_lock(&GlobalSMBSeslock);
         /* we could simply get the first_list_entry since write-only entries
@@ -1179,6 +1185,8 @@ struct cifsFileInfo *find_readable_file(struct cifsInodeInfo *cifs_inode)
         list_for_each_entry(open_file, &cifs_inode->openFileList, flist) {
                 if (open_file->closePend)
                         continue;
+                if (fsuid_only && open_file->uid != current_fsuid())
+                        continue;
                 if (open_file->pfile && ((open_file->pfile->f_flags & O_RDWR) ||
                     (open_file->pfile->f_flags & O_RDONLY))) {
                         if (!open_file->invalidHandle) {
@@ -1198,9 +1206,11 @@ struct cifsFileInfo *find_readable_file(struct cifsInodeInfo *cifs_inode)
 }
 #endif
 
-struct cifsFileInfo *find_writable_file(struct cifsInodeInfo *cifs_inode)
+struct cifsFileInfo *find_writable_file(struct cifsInodeInfo *cifs_inode,
+                                        bool fsuid_only)
 {
         struct cifsFileInfo *open_file;
+        struct cifs_sb_info *cifs_sb = CIFS_SB(cifs_inode->vfs_inode.i_sb);
         bool any_available = false;
         int rc;
 
@@ -1214,13 +1224,19 @@ struct cifsFileInfo *find_writable_file(struct cifsInodeInfo *cifs_inode)
                 return NULL;
         }
 
+        /* only filter by fsuid on multiuser mounts */
+        if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MULTIUSER))
+                fsuid_only = false;
+
         read_lock(&GlobalSMBSeslock);
 refind_writable:
         list_for_each_entry(open_file, &cifs_inode->openFileList, flist) {
-                if (open_file->closePend ||
-                    (!any_available && open_file->pid != current->tgid))
+                if (open_file->closePend)
+                        continue;
+                if (!any_available && open_file->pid != current->tgid)
+                        continue;
+                if (fsuid_only && open_file->uid != current_fsuid())
                         continue;
-
                 if (open_file->pfile &&
                     ((open_file->pfile->f_flags & O_RDWR) ||
                      (open_file->pfile->f_flags & O_WRONLY))) {
@@ -1315,7 +1331,7 @@ static int cifs_partialpagewrite(struct page *page, unsigned from, unsigned to)
         if (mapping->host->i_size - offset < (loff_t)to)
                 to = (unsigned)(mapping->host->i_size - offset);
 
-        open_file = find_writable_file(CIFS_I(mapping->host));
+        open_file = find_writable_file(CIFS_I(mapping->host), false);
         if (open_file) {
                 bytes_written = cifs_write(open_file->pfile, write_data,
                                            to-from, &offset);
@@ -1388,7 +1404,7 @@ static int cifs_writepages(struct address_space *mapping,
          * but it'll at least handle the return. Maybe it should be
          * a BUG() instead?
          */
-        open_file = find_writable_file(CIFS_I(mapping->host));
+        open_file = find_writable_file(CIFS_I(mapping->host), false);
         if (!open_file) {
                 kfree(iov);
                 return generic_writepages(mapping, wbc);
@@ -1505,7 +1521,8 @@ retry:
                                 break;
                 }
                 if (n_iov) {
-                        open_file = find_writable_file(CIFS_I(mapping->host));
+                        open_file = find_writable_file(CIFS_I(mapping->host),
+                                                        false);
                         if (!open_file) {
                                 cERROR(1, "No writable handles for inode");
                                 rc = -EBADF;