From d0e13f5bbe4be7c8f27736fc40503dcec04b7de0 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Wed, 15 Jun 2016 14:18:59 +0200 Subject: [PATCH] ovl: fix uid/gid when creating over whiteout Fix a regression when creating a file over a whiteout. The new file/directory needs to use the current fsuid/fsgid, not the ones from the mounter's credentials. The refcounting is a bit tricky: prepare_creds() sets an original refcount, override_creds() gets one more, which revert_cred() drops. So 1) we need to expicitly put the mounter's credentials when overriding with the updated one 2) we need to put the original ref to the updated creds (and this can safely be done before revert_creds(), since we'll still have the ref from override_creds()). Reported-by: Stephen Smalley Fixes: 3fe6e52f0626 ("ovl: override creds with the ones from the superblock mounter") Signed-off-by: Miklos Szeredi --- fs/overlayfs/dir.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c index 22f0253a3567..c2a6b0894022 100644 --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -405,12 +405,21 @@ static int ovl_create_or_link(struct dentry *dentry, int mode, dev_t rdev, err = ovl_create_upper(dentry, inode, &stat, link, hardlink); } else { const struct cred *old_cred; + struct cred *override_cred; old_cred = ovl_override_creds(dentry->d_sb); - err = ovl_create_over_whiteout(dentry, inode, &stat, link, - hardlink); + err = -ENOMEM; + override_cred = prepare_creds(); + if (override_cred) { + override_cred->fsuid = old_cred->fsuid; + override_cred->fsgid = old_cred->fsgid; + put_cred(override_creds(override_cred)); + put_cred(override_cred); + err = ovl_create_over_whiteout(dentry, inode, &stat, + link, hardlink); + } revert_creds(old_cred); } -- 2.30.2