From cf9a6784f7c1b5ee2b9159a1246e327c331c5697 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Fri, 11 Dec 2015 16:30:49 +0100 Subject: [PATCH] ovl: setattr: check permissions before copy-up Without this copy-up of a file can be forced, even without actually being allowed to do anything on the file. [Arnd Bergmann] include for PAGE_CACHE_SIZE (used by MAX_LFS_FILESIZE definition). Signed-off-by: Miklos Szeredi Cc: --- fs/overlayfs/inode.c | 13 +++++++++++++ fs/overlayfs/super.c | 2 ++ 2 files changed, 15 insertions(+) diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index 76546314e35f..213a726cff96 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -45,6 +45,19 @@ int ovl_setattr(struct dentry *dentry, struct iattr *attr) int err; struct dentry *upperdentry; + /* + * Check for permissions before trying to copy-up. This is redundant + * since it will be rechecked later by ->setattr() on upper dentry. But + * without this, copy-up can be triggered by just about anybody. + * + * We don't initialize inode->size, which just means that + * inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not + * check for a swapfile (which this won't be anyway). + */ + err = inode_change_ok(dentry->d_inode, attr); + if (err) + return err; + err = ovl_want_write(dentry); if (err) goto out; diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index ec31711d4886..b08bf4d3a405 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -9,6 +9,7 @@ #include #include +#include #include #include #include @@ -936,6 +937,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) } sb->s_stack_depth = 0; + sb->s_maxbytes = MAX_LFS_FILESIZE; if (ufs->config.upperdir) { if (!ufs->config.workdir) { pr_err("overlayfs: missing 'workdir'\n");