From f2b20f6ee842313a0d681dbbf7f87b70291a6a3b Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Fri, 16 Sep 2016 12:44:20 +0200 Subject: vfs: move permission checking into notify_change() for utimes(NULL) This fixes a bug where the permission was not properly checked in overlayfs. The testcase is ltp/utimensat01. It is also cleaner and safer to do the permission checking in the vfs helper instead of the caller. This patch introduces an additional ia_valid flag ATTR_TOUCH (since touch(1) is the most obvious user of utimes(NULL)) that is passed into notify_change whenever the conditions for this special permission checking mode are met. Reported-by: Aihua Zhang Signed-off-by: Miklos Szeredi Tested-by: Aihua Zhang Cc: # v3.18+ --- fs/attr.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'fs/attr.c') diff --git a/fs/attr.c b/fs/attr.c index 42bb42bb3c72..3c42cab06b5d 100644 --- a/fs/attr.c +++ b/fs/attr.c @@ -202,6 +202,21 @@ int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **de return -EPERM; } + /* + * If utimes(2) and friends are called with times == NULL (or both + * times are UTIME_NOW), then we need to check for write permission + */ + if (ia_valid & ATTR_TOUCH) { + if (IS_IMMUTABLE(inode)) + return -EPERM; + + if (!inode_owner_or_capable(inode)) { + error = inode_permission(inode, MAY_WRITE); + if (error) + return error; + } + } + if ((ia_valid & ATTR_MODE)) { umode_t amode = attr->ia_mode; /* Flag setting protected by i_mutex */ -- cgit v1.2.3