linux/fs/configfs
Al Viro 351e5d869e configfs: fix a deadlock in configfs_symlink()
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>
2019-09-11 12:45:49 +02:00
..
configfs_internal.h configfs: new object reprsenting tree fragments 2019-09-02 22:10:44 +02:00
dir.c configfs: provide exclusion between IO and removals 2019-09-04 22:33:51 +02:00
file.c configfs: provide exclusion between IO and removals 2019-09-04 22:33:51 +02:00
inode.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 145 2019-05-30 11:25:18 -07:00
item.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 145 2019-05-30 11:25:18 -07:00
Kconfig treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Makefile treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
mount.c Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
symlink.c configfs: fix a deadlock in configfs_symlink() 2019-09-11 12:45:49 +02:00