ovl: pass original credentials, not mounter credentials during create

When creating new files the security layer expects the original
credentials to be passed.  When cleaning up the code this was accidently
changed to pass the mounter's credentials by relying on current->cred
which is already overriden at this point.  Pass the original credentials
directly.

Reported-by: Ondrej Mosnacek <omosnace@redhat.com>
Reported-by: Paul Moore <paul@paul-moore.com>
Fixes: e566bff96322 ("ovl: port ovl_create_or_link() to new ovl_override_creator_creds")
Link: https://lore.kernel.org/CAFqZXNvL1ciLXMhHrnoyBmQu1PAApH41LkSWEhrcvzAAbFij8Q@mail.gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Tested-by: Ondrej Mosnacek <omosnace@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 06b860b9ded6b25ed9762a46f7e26e98e97a8dea..ff3dbd1ca61f280d1495bb52182a2da9a6b28119 100644 (file)
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -581,7 +581,8 @@ out_cleanup_unlocked:
        goto out_dput;
 }
 
-static const struct cred *ovl_override_creator_creds(struct dentry *dentry, struct inode *inode, umode_t mode)
+static const struct cred *ovl_override_creator_creds(const struct cred *original_creds,
+                                                    struct dentry *dentry, struct inode *inode, umode_t mode)
 {
        int err;
 
@@ -596,7 +597,7 @@ static const struct cred *ovl_override_creator_creds(struct dentry *dentry, stru
        override_cred->fsgid = inode->i_gid;
 
        err = security_dentry_create_files_as(dentry, mode, &dentry->d_name,
-                                             current->cred, override_cred);
+                                             original_creds, override_cred);
        if (err)
                return ERR_PTR(err);
 
@@ -614,8 +615,11 @@ static void ovl_revert_creator_creds(const struct cred *old_cred)
 DEFINE_CLASS(ovl_override_creator_creds,
             const struct cred *,
             if (!IS_ERR_OR_NULL(_T)) ovl_revert_creator_creds(_T),
-            ovl_override_creator_creds(dentry, inode, mode),
-            struct dentry *dentry, struct inode *inode, umode_t mode)
+            ovl_override_creator_creds(original_creds, dentry, inode, mode),
+            const struct cred *original_creds,
+            struct dentry *dentry,
+            struct inode *inode,
+            umode_t mode)
 
 static int ovl_create_handle_whiteouts(struct dentry *dentry,
                                       struct inode *inode,
@@ -633,7 +637,7 @@ static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
        int err;
        struct dentry *parent = dentry->d_parent;
 
-       with_ovl_creds(dentry->d_sb) {
+       scoped_class(override_creds_ovl, original_creds, dentry->d_sb) {
                /*
                 * When linking a file with copy up origin into a new parent, mark the
                 * new parent dir "impure".
@@ -661,7 +665,7 @@ static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
                if (attr->hardlink)
                        return ovl_create_handle_whiteouts(dentry, inode, attr);
 
-               scoped_class(ovl_override_creator_creds, cred, dentry, inode, attr->mode) {
+               scoped_class(ovl_override_creator_creds, cred, original_creds, dentry, inode, attr->mode) {
                        if (IS_ERR(cred))
                                return PTR_ERR(cred);
                        return ovl_create_handle_whiteouts(dentry, inode, attr);
@@ -1364,8 +1368,8 @@ static int ovl_create_tmpfile(struct file *file, struct dentry *dentry,
        int flags = file->f_flags | OVL_OPEN_FLAGS;
        int err;
 
-       with_ovl_creds(dentry->d_sb) {
-               scoped_class(ovl_override_creator_creds, cred, dentry, inode, mode) {
+       scoped_class(override_creds_ovl, original_creds, dentry->d_sb) {
+               scoped_class(ovl_override_creator_creds, cred, original_creds, dentry, inode, mode) {
                        if (IS_ERR(cred))
                                return PTR_ERR(cred);