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kernfs: The cgroup filesystem also benefits from SB_I_NOEXEC

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The cgroup filesystem is in the same boat as sysfs.  No one ever
permits executables of any kind on the cgroup filesystem, and there is
no reasonable future case to support executables in the future.

Therefore move the setting of SB_I_NOEXEC which makes the code proof
against future mistakes of accidentally creating executables from
sysfs to kernfs itself.  Making the code simpler and covering the
sysfs, cgroup, and cgroup2 filesystems.

Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2016-06-10 13:03:05 -05:00
parent a001e74cef
commit 29a517c232
2 changed files with 3 additions and 2 deletions
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2
fs/kernfs/mount.c
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@ -152,6 +152,8 @@ static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
struct dentry *root;
info->sb = sb;
/* Userspace would break if executables appear on sysfs */
sb->s_iflags |= SB_I_NOEXEC;
sb->s_blocksize = PAGE_SIZE;
sb->s_blocksize_bits = PAGE_SHIFT;
sb->s_magic = magic;

3
fs/sysfs/mount.c
View file

@ -41,8 +41,7 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type,
if (IS_ERR(root) || !new_sb)
kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
else if (new_sb)
/* Userspace would break if executables appear on sysfs */
root->d_sb->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC;
root->d_sb->s_iflags |= SB_I_USERNS_VISIBLE;
return root;
}