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commit 351e5d869e5ac10cb40c78b5f2d7dfc816ad4587 upstream. Configfs abuses symlink(2). Unlike the normal filesystems, it wants the target resolved at symlink(2) time, like link(2) would've done. The problem is that ->symlink() is called with the parent directory locked exclusive, so resolving the target inside the ->symlink() is easily deadlocked. Short of really ugly games in sys_symlink() itself, all we can do is to unlock the parent before resolving the target and relock it after. However, that invalidates the checks done by the caller of ->symlink(), so we have to * check that dentry is still where it used to be (it couldn't have been moved, but it could've been unhashed) * recheck that it's still negative (somebody else might've successfully created a symlink with the same name while we were looking the target up) * recheck the permissions on the parent directory. Cc: stable@vger.kernel.org Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.