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authorAl Viro <viro@zeniv.linux.org.uk>2011-11-22 21:31:21 +0400
committerAl Viro <viro@zeniv.linux.org.uk>2011-11-22 21:31:21 +0400
commitd31da0f0ba3bc0a827a63879310818c22d9a95be (patch)
treed89bbdf299c4cbc37f49a9964b8127f09eedd50b /fs
parentb46413367961c2e8bd827e067a231be982aaeee2 (diff)
downloadlinux-d31da0f0ba3bc0a827a63879310818c22d9a95be.tar.xz
mount_subtree() pointless use-after-free
d'oh... we'd carefully pinned mnt->mnt_sb down, dropped mnt and attempt to grab s_umount on mnt->mnt_sb. The trouble is, *mnt might've been overwritten by now... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs')
-rw-r--r--fs/namespace.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index 50ee30345b4f..6d3a1963879b 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2493,6 +2493,7 @@ EXPORT_SYMBOL(create_mnt_ns);
struct dentry *mount_subtree(struct vfsmount *mnt, const char *name)
{
struct mnt_namespace *ns;
+ struct super_block *s;
struct path path;
int err;
@@ -2509,10 +2510,11 @@ struct dentry *mount_subtree(struct vfsmount *mnt, const char *name)
return ERR_PTR(err);
/* trade a vfsmount reference for active sb one */
- atomic_inc(&path.mnt->mnt_sb->s_active);
+ s = path.mnt->mnt_sb;
+ atomic_inc(&s->s_active);
mntput(path.mnt);
/* lock the sucker */
- down_write(&path.mnt->mnt_sb->s_umount);
+ down_write(&s->s_umount);
/* ... and return the root of (sub)tree on it */
return path.dentry;
}