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mount: consolidate permission checks 

... and ask for global CAP_SYS_ADMIN only for superblock-level remounts

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2013-02-22 22:49:10 -05:00
parent 9b40bc90ab
commit 57eccb830f
1 changed files with 7 additions and 33 deletions
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40
fs/namespace.c
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@ -1300,24 +1300,6 @@ SYSCALL_DEFINE1(oldumount, char __user *, name)
#endif #endif
static int mount_is_safe(struct path *path)
{
if (may_mount())
return 0;
return -EPERM;
#ifdef notyet
if (S_ISLNK(path->dentry->d_inode->i_mode))
return -EPERM;
if (path->dentry->d_inode->i_mode & S_ISVTX) {
if (current_uid() != path->dentry->d_inode->i_uid)
return -EPERM;
}
if (inode_permission(path->dentry->d_inode, MAY_WRITE))
return -EPERM;
return 0;
#endif
}
static bool mnt_ns_loop(struct path *path) static bool mnt_ns_loop(struct path *path)
{ {
/* Could bind mounting the mount namespace inode cause a /* Could bind mounting the mount namespace inode cause a
@ -1640,9 +1622,6 @@ static int do_change_type(struct path *path, int flag)
int type; int type;
int err = 0; int err = 0;
if (!may_mount())
return -EPERM;
if (path->dentry != path->mnt->mnt_root) if (path->dentry != path->mnt->mnt_root)
return -EINVAL; return -EINVAL;
@ -1676,9 +1655,7 @@ static int do_loopback(struct path *path, const char *old_name,
LIST_HEAD(umount_list); LIST_HEAD(umount_list);
struct path old_path; struct path old_path;
struct mount *mnt = NULL, *old; struct mount *mnt = NULL, *old;
int err = mount_is_safe(path); int err;
if (err)
return err;
if (!old_name || !*old_name) if (!old_name || !*old_name)
return -EINVAL; return -EINVAL;
err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
@ -1755,9 +1732,6 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
struct super_block *sb = path->mnt->mnt_sb; struct super_block *sb = path->mnt->mnt_sb;
struct mount *mnt = real_mount(path->mnt); struct mount *mnt = real_mount(path->mnt);
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (!check_mnt(mnt)) if (!check_mnt(mnt))
return -EINVAL; return -EINVAL;
@ -1771,6 +1745,8 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
down_write(&sb->s_umount); down_write(&sb->s_umount);
if (flags & MS_BIND) if (flags & MS_BIND)
err = change_mount_flags(path->mnt, flags); err = change_mount_flags(path->mnt, flags);
else if (!capable(CAP_SYS_ADMIN))
err = -EPERM;
else else
err = do_remount_sb(sb, flags, data, 0); err = do_remount_sb(sb, flags, data, 0);
if (!err) { if (!err) {
@ -1803,9 +1779,7 @@ static int do_move_mount(struct path *path, const char *old_name)
struct path old_path, parent_path; struct path old_path, parent_path;
struct mount *p; struct mount *p;
struct mount *old; struct mount *old;
int err = 0; int err;
if (!may_mount())
return -EPERM;
if (!old_name || !*old_name) if (!old_name || !*old_name)
return -EINVAL; return -EINVAL;
err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
@ -1947,9 +1921,6 @@ static int do_new_mount(struct path *path, const char *fstype, int flags,
if (!fstype) if (!fstype)
return -EINVAL; return -EINVAL;
if (!may_mount())
return -EPERM;
type = get_fs_type(fstype); type = get_fs_type(fstype);
if (!type) if (!type)
return -ENODEV; return -ENODEV;
@ -2263,6 +2234,9 @@ long do_mount(const char *dev_name, const char *dir_name,
if (retval) if (retval)
goto dput_out; goto dput_out;
if (!may_mount())
return -EPERM;
/* Default to relatime unless overriden */ /* Default to relatime unless overriden */
if (!(flags & MS_NOATIME)) if (!(flags & MS_NOATIME))
mnt_flags |= MNT_RELATIME; mnt_flags |= MNT_RELATIME;