From a7560a0132cfc93b25d2df1d277a078a05220cf4 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 10 Dec 2013 10:22:30 -0500 Subject: [PATCH] sysfs: fix use-after-free in sysfs_kill_sb() While restructuring the [u]mount path, 4b93dc9b1c68 ("sysfs, kernfs: prepare mount path for kernfs") incorrectly updated sysfs_kill_sb() so that it first kills super_block and then tries to dereference its namespace tag to drop it. Fix it by caching namespace tag before killing the superblock and then drop the cached namespace tag. Signed-off-by: Tejun Heo Reported-by: Yuanhan Liu Tested-by: Yuanhan Liu Tested-by: Vlastimil Babka Link: http://lkml.kernel.org/g/20131205031051.GC5135@yliu-dev.sh.intel.com Signed-off-by: Greg Kroah-Hartman --- fs/sysfs/mount.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c index e7e3aa8e7b78..8d075272cace 100644 --- a/fs/sysfs/mount.c +++ b/fs/sysfs/mount.c @@ -45,8 +45,10 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type, static void sysfs_kill_sb(struct super_block *sb) { + void *ns = (void *)kernfs_super_ns(sb); + kernfs_kill_sb(sb); - kobj_ns_drop(KOBJ_NS_TYPE_NET, (void *)kernfs_super_ns(sb)); + kobj_ns_drop(KOBJ_NS_TYPE_NET, ns); } static struct file_system_type sysfs_fs_type = {