sysfs: Fix locking and factor out sysfs_sd_setattr

Cleanly separate the work that is specific to setting the
attributes of a sysfs_dirent from what is needed to update
the attributes of a vfs inode.

Additionally grab the sysfs_mutex to keep any nasties from
surprising us when updating the sysfs_dirent.

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 32 insertions, 20 deletions

diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index 86fb230de432..76e977c300f7 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -65,30 +65,14 @@ static struct sysfs_inode_attrs *sysfs_init_inode_attrs(struct sysfs_dirent *sd)
         return attrs;
 }
 
-int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
+int sysfs_sd_setattr(struct sysfs_dirent *sd, struct iattr * iattr)
 {
-        struct inode * inode = dentry->d_inode;
-        struct sysfs_dirent * sd = dentry->d_fsdata;
         struct sysfs_inode_attrs *sd_attrs;
         struct iattr *iattrs;
         unsigned int ia_valid = iattr->ia_valid;
-        int error;
-
-        if (!sd)
-                return -EINVAL;
 
         sd_attrs = sd->s_iattr;
 
-        error = inode_change_ok(inode, iattr);
-        if (error)
-                return error;
-
-        iattr->ia_valid &= ~ATTR_SIZE; /* ignore size changes */
-
-        error = inode_setattr(inode, iattr);
-        if (error)
-                return error;
-
         if (!sd_attrs) {
                 /* setting attributes for the first time, allocate now */
                 sd_attrs = sysfs_init_inode_attrs(sd);
@@ -111,12 +95,39 @@ int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
                         iattrs->ia_ctime = iattr->ia_ctime;
                 if (ia_valid & ATTR_MODE) {
                         umode_t mode = iattr->ia_mode;
-
-                        if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
-                                mode &= ~S_ISGID;
                         iattrs->ia_mode = sd->s_mode = mode;
                 }
         }
+        return 0;
+}
+
+int sysfs_setattr(struct dentry *dentry, struct iattr *iattr)
+{
+        struct inode *inode = dentry->d_inode;
+        struct sysfs_dirent *sd = dentry->d_fsdata;
+        int error;
+
+        if (!sd)
+                return -EINVAL;
+
+        error = inode_change_ok(inode, iattr);
+        if (error)
+                return error;
+
+        iattr->ia_valid &= ~ATTR_SIZE; /* ignore size changes */
+        if (iattr->ia_valid & ATTR_MODE) {
+                if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
+                        iattr->ia_mode &= ~S_ISGID;
+        }
+
+        error = inode_setattr(inode, iattr);
+        if (error)
+                return error;
+
+        mutex_lock(&sysfs_mutex);
+        error = sysfs_sd_setattr(sd, iattr);
+        mutex_unlock(&sysfs_mutex);
+
         return error;
 }
 
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index af4c4e7482ac..a96d9678ae73 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -155,6 +155,7 @@ static inline void __sysfs_put(struct sysfs_dirent *sd)
  */
 struct inode *sysfs_get_inode(struct sysfs_dirent *sd);
 void sysfs_delete_inode(struct inode *inode);
+int sysfs_sd_setattr(struct sysfs_dirent *sd, struct iattr *iattr);
 int sysfs_setattr(struct dentry *dentry, struct iattr *iattr);
 int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
                 size_t size, int flags);