cgroup: fix broken file xattrs

We should store file xattrs in struct cfent instead of struct cftype,
because cftype is a type while cfent is object instance of cftype.

For example each cgroup has a tasks file, and each tasks file is
associated with a uniq cfent, but all those files share the same
struct cftype.

Alexey Kodanev reported a crash, which can be reproduced:

  # mount -t cgroup -o xattr /sys/fs/cgroup
  # mkdir /sys/fs/cgroup/test
  # setfattr -n trusted.value -v test_value /sys/fs/cgroup/tasks
  # rmdir /sys/fs/cgroup/test
  # umount /sys/fs/cgroup
  oops!

In this case, simple_xattrs_free() will free the same struct simple_xattrs
twice.

tj: Dropped unused local variable @cft from cgroup_diput().

Cc: <stable@vger.kernel.org> # 3.8.x
Reported-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index cda7eb2..c371888 100644 (file)
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -422,9 +422,6 @@ struct cftype {
        /* CFTYPE_* flags */
        unsigned int flags;
 
-       /* file xattrs */
-       struct simple_xattrs xattrs;
-
        int (*open)(struct inode *inode, struct file *file);
        ssize_t (*read)(struct cgroup *cgrp, struct cftype *cft,
                        struct file *file,

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index c16719e..192d762 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -117,6 +117,9 @@ struct cfent {
        struct list_head                node;
        struct dentry                   *dentry;
        struct cftype                   *type;
+
+       /* file xattrs */
+       struct simple_xattrs            xattrs;
 };
 
 /*
@@ -882,13 +885,12 @@ static void cgroup_diput(struct dentry *dentry, struct inode *inode)
        } else {
                struct cfent *cfe = __d_cfe(dentry);
                struct cgroup *cgrp = dentry->d_parent->d_fsdata;
-               struct cftype *cft = cfe->type;
 
                WARN_ONCE(!list_empty(&cfe->node) &&
                          cgrp != &cgrp->root->top_cgroup,
                          "cfe still linked for %s\n", cfe->type->name);
+               simple_xattrs_free(&cfe->xattrs);
                kfree(cfe);
-               simple_xattrs_free(&cft->xattrs);
        }
        iput(inode);
 }
@@ -2501,7 +2503,7 @@ static struct simple_xattrs *__d_xattrs(struct dentry *dentry)
        if (S_ISDIR(dentry->d_inode->i_mode))
                return &__d_cgrp(dentry)->xattrs;
        else
-               return &__d_cft(dentry)->xattrs;
+               return &__d_cfe(dentry)->xattrs;
 }
 
 static inline int xattr_enabled(struct dentry *dentry)
@@ -2677,8 +2679,6 @@ static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
        umode_t mode;
        char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
 
-       simple_xattrs_init(&cft->xattrs);
-
        if (subsys && !(cgrp->root->flags & CGRP_ROOT_NOPREFIX)) {
                strcpy(name, subsys->name);
                strcat(name, ".");
@@ -2703,6 +2703,7 @@ static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
                cfe->type = (void *)cft;
                cfe->dentry = dentry;
                dentry->d_fsdata = cfe;
+               simple_xattrs_init(&cfe->xattrs);
                list_add_tail(&cfe->node, &parent->files);
                cfe = NULL;
        }