cgroups: fix a serious bug in cgroupstats
authorLi Zefan <lizf@cn.fujitsu.com>
Wed, 19 Nov 2008 23:36:48 +0000 (15:36 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 20 Nov 2008 02:50:00 +0000 (18:50 -0800)
Try this, and you'll get oops immediately:
 # cd Documentation/accounting/
 # gcc -o getdelays getdelays.c
 # mount -t cgroup -o debug xxx /mnt
 # ./getdelays -C /mnt/tasks

Because a normal file's dentry->d_fsdata is a pointer to struct cftype,
not struct cgroup.

After the patch, it returns EINVAL if we try to get cgroupstats
from a normal file.

Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Paul Menage <menage@google.com>
Cc: <stable@kernel.org> [2.6.25.x, 2.6.26.x, 2.6.27.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
kernel/cgroup.c

index 1a06be6..fe00b3b 100644 (file)
@@ -2039,10 +2039,13 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
        struct cgroup *cgrp;
        struct cgroup_iter it;
        struct task_struct *tsk;
+
        /*
-        * Validate dentry by checking the superblock operations
+        * Validate dentry by checking the superblock operations,
+        * and make sure it's a directory.
         */
-       if (dentry->d_sb->s_op != &cgroup_ops)
+       if (dentry->d_sb->s_op != &cgroup_ops ||
+           !S_ISDIR(dentry->d_inode->i_mode))
                 goto err;
 
        ret = 0;