ubi: Don't bypass ->getattr()

Directly accessing inode fields bypasses ->getattr()
and can cause problems when the underlying filesystem
does not have the default ->getattr() implementation.

So instead of obtaining the backing inode via d_backing_inode()
use vfs_getattr() and obtain what we need from the kstat struct.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>

2 files changed, 20 insertions, 13 deletions

diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 7091fca0fb44..ef3618299494 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -1147,22 +1147,26 @@ int ubi_detach_mtd_dev(int ubi_num, int anyway)
  */
 static struct mtd_info * __init open_mtd_by_chdev(const char *mtd_dev)
 {
-        int err, major, minor, mode;
+        int err, minor;
         struct path path;
+        struct kstat stat;
 
         /* Probably this is an MTD character device node path */
         err = kern_path(mtd_dev, LOOKUP_FOLLOW, &path);
         if (err)
                 return ERR_PTR(err);
 
-        /* MTD device number is defined by the major / minor numbers */
-        major = imajor(d_backing_inode(path.dentry));
-        minor = iminor(d_backing_inode(path.dentry));
-        mode = d_backing_inode(path.dentry)->i_mode;
+        err = vfs_getattr(&path, &stat);
         path_put(&path);
-        if (major != MTD_CHAR_MAJOR || !S_ISCHR(mode))
+        if (err)
+                return ERR_PTR(err);
+
+        /* MTD device number is defined by the major / minor numbers */
+        if (MAJOR(stat.rdev) != MTD_CHAR_MAJOR || !S_ISCHR(stat.mode))
                 return ERR_PTR(-EINVAL);
 
+        minor = MINOR(stat.rdev);
+
         if (minor & 1)
                 /*
                  * Just do not think the "/dev/mtdrX" devices support is need,
diff --git a/drivers/mtd/ubi/kapi.c b/drivers/mtd/ubi/kapi.c
index cc6fa0115c9a..a9e2cef7c95c 100644
--- a/drivers/mtd/ubi/kapi.c
+++ b/drivers/mtd/ubi/kapi.c
@@ -301,9 +301,9 @@ EXPORT_SYMBOL_GPL(ubi_open_volume_nm);
  */
 struct ubi_volume_desc *ubi_open_volume_path(const char *pathname, int mode)
 {
-        int error, ubi_num, vol_id, mod;
-        struct inode *inode;
+        int error, ubi_num, vol_id;
         struct path path;
+        struct kstat stat;
 
         dbg_gen("open volume %s, mode %d", pathname, mode);
 
@@ -314,14 +314,17 @@ struct ubi_volume_desc *ubi_open_volume_path(const char *pathname, int mode)
         if (error)
                 return ERR_PTR(error);
 
-        inode = d_backing_inode(path.dentry);
-        mod = inode->i_mode;
-        ubi_num = ubi_major2num(imajor(inode));
-        vol_id = iminor(inode) - 1;
+        error = vfs_getattr(&path, &stat);
         path_put(&path);
+        if (error)
+                return ERR_PTR(error);
 
-        if (!S_ISCHR(mod))
+        if (!S_ISCHR(stat.mode))
                 return ERR_PTR(-EINVAL);
+
+        ubi_num = ubi_major2num(MAJOR(stat.rdev));
+        vol_id = MINOR(stat.rdev) - 1;
+
         if (vol_id >= 0 && ubi_num >= 0)
                 return ubi_open_volume(ubi_num, vol_id, mode);
         return ERR_PTR(-ENODEV);