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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>
This commit is contained in:
Li Zefan 2013-04-18 23:09:52 -07:00 committed by Tejun Heo
parent e57d5cf2f8
commit 712317ad97
2 changed files with 6 additions and 8 deletions
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3
include/linux/cgroup.h
View File

@ -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,

11
kernel/cgroup.c
View File

@ -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;
}