Re: [PATCH] vfs: move getname() from callers to do_mount()

From: Jeff Layton
Date: Sun Sep 14 2014 - 09:37:27 EST

On Sun, 14 Sep 2014 22:15:10 +0900
Seunghun Lee <waydi1@xxxxxxxxx> wrote:

> It would make more sense to pass char __user * instead of
> char * in callers of do_mount() and do getname() inside do_mount().
>
> Suggested-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Seunghun Lee <waydi1@xxxxxxxxx>
> ---
> arch/alpha/kernel/osf_sys.c | 23 ++++++++++-------------
> fs/compat.c | 20 ++++++--------------
> fs/namespace.c | 29 ++++++++++++-----------------
> include/linux/fs.h | 3 ++-
> 4 files changed, 30 insertions(+), 45 deletions(-)
>
> diff --git a/arch/alpha/kernel/osf_sys.c b/arch/alpha/kernel/osf_sys.c
> index 1402fcc..f9c732e 100644
> --- a/arch/alpha/kernel/osf_sys.c
> +++ b/arch/alpha/kernel/osf_sys.c
> @@ -446,7 +446,8 @@ struct procfs_args {
> * unhappy with OSF UFS. [CHECKME]
> */
> static int
> -osf_ufs_mount(const char *dirname, struct ufs_args __user *args, int flags)
> +osf_ufs_mount(const char __user *dirname,
> + struct ufs_args __user *args, int flags)
> {
> int retval;
> struct cdfs_args tmp;
> @@ -466,7 +467,8 @@ osf_ufs_mount(const char *dirname, struct ufs_args __user *args, int flags)
> }
>
> static int
> -osf_cdfs_mount(const char *dirname, struct cdfs_args __user *args, int flags)
> +osf_cdfs_mount(const char __user *dirname,
> + struct cdfs_args __user *args, int flags)
> {
> int retval;
> struct cdfs_args tmp;
> @@ -486,7 +488,8 @@ osf_cdfs_mount(const char *dirname, struct cdfs_args __user *args, int flags)
> }
>
> static int
> -osf_procfs_mount(const char *dirname, struct procfs_args __user *args, int flags)
> +osf_procfs_mount(const char __user *dirname,
> + struct procfs_args __user *args, int flags)
> {
> struct procfs_args tmp;
>
> @@ -500,28 +503,22 @@ SYSCALL_DEFINE4(osf_mount, unsigned long, typenr, const char __user *, path,
> int, flag, void __user *, data)
> {
> int retval;
> - struct filename *name;
>
> - name = getname(path);
> - retval = PTR_ERR(name);
> - if (IS_ERR(name))
> - goto out;
> switch (typenr) {
> case 1:
> - retval = osf_ufs_mount(name->name, data, flag);
> + retval = osf_ufs_mount(path, data, flag);
> break;
> case 6:
> - retval = osf_cdfs_mount(name->name, data, flag);
> + retval = osf_cdfs_mount(path, data, flag);
> break;
> case 9:
> - retval = osf_procfs_mount(name->name, data, flag);
> + retval = osf_procfs_mount(path, data, flag);
> break;
> default:
> retval = -EINVAL;
> printk("osf_mount(%ld, %x)\n", typenr, flag);
> }
> - putname(name);
> - out:
> +
> return retval;
> }
>
> diff --git a/fs/compat.c b/fs/compat.c
> index 6205c24..b13df99 100644
> --- a/fs/compat.c
> +++ b/fs/compat.c
> @@ -794,7 +794,6 @@ COMPAT_SYSCALL_DEFINE5(mount, const char __user *, dev_name,
> char *kernel_type;
> unsigned long data_page;
> char *kernel_dev;
> - struct filename *dir;
> int retval;
>
> kernel_type = copy_mount_string(type);
> @@ -802,19 +801,14 @@ COMPAT_SYSCALL_DEFINE5(mount, const char __user *, dev_name,
> if (IS_ERR(kernel_type))
> goto out;
>
> - dir = getname(dir_name);
> - retval = PTR_ERR(dir);
> - if (IS_ERR(dir))
> - goto out1;
> -
> kernel_dev = copy_mount_string(dev_name);
> retval = PTR_ERR(kernel_dev);
> if (IS_ERR(kernel_dev))
> - goto out2;
> + goto out1;
>
> retval = copy_mount_options(data, &data_page);
> if (retval < 0)
> - goto out3;
> + goto out2;
>
> retval = -EINVAL;
>
> @@ -823,19 +817,17 @@ COMPAT_SYSCALL_DEFINE5(mount, const char __user *, dev_name,
> do_ncp_super_data_conv((void *)data_page);
> } else if (!strcmp(kernel_type, NFS4_NAME)) {
> if (do_nfs4_super_data_conv((void *) data_page))
> - goto out4;
> + goto out3;
> }
> }
>
> - retval = do_mount(kernel_dev, dir->name, kernel_type,
> + retval = do_mount(kernel_dev, dir_name, kernel_type,
> flags, (void*)data_page);
>
> - out4:
> - free_page(data_page);
> out3:
> - kfree(kernel_dev);
> + free_page(data_page);
> out2:
> - putname(dir);
> + kfree(kernel_dev);
> out1:
> kfree(kernel_type);
> out:
> diff --git a/fs/namespace.c b/fs/namespace.c
> index bfd03c6..3e11e9e 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -2542,9 +2542,10 @@ char *copy_mount_string(const void __user *data)
> * Therefore, if this magic number is present, it carries no information
> * and must be discarded.
> */
> -long do_mount(const char *dev_name, const char *dir_name,
> +long do_mount(const char *dev_name, const char __user *dir_name,
> const char *type_page, unsigned long flags, void *data_page)
> {
> + struct filename *kernel_dir;
> struct path path;
> int retval = 0;
> int mnt_flags = 0;
> @@ -2553,18 +2554,19 @@ long do_mount(const char *dev_name, const char *dir_name,
> if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
> flags &= ~MS_MGC_MSK;
>
> - /* Basic sanity checks */
> -
> - if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
> - return -EINVAL;
> + kernel_dir = getname(dir_name);
> + if (IS_ERR(kernel_dir)) {
> + retval = PTR_ERR(kernel_dir);
> + return retval;
> + }
>
> if (data_page)
> ((char *)data_page)[PAGE_SIZE - 1] = 0;
>
> /* ... and get the mountpoint */
> - retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);
> + retval = kern_path(kernel_dir->name, LOOKUP_FOLLOW, &path);
> if (retval)
> - return retval;
> + goto dir_out;
>
> retval = security_sb_mount(dev_name, &path,
> type_page, flags, data_page);
> @@ -2619,6 +2621,8 @@ long do_mount(const char *dev_name, const char *dir_name,
> dev_name, data_page);
> dput_out:
> path_put(&path);
> +dir_out:
> + putname(kernel_dir);
> return retval;
> }
>
> @@ -2787,7 +2791,6 @@ SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
> {
> int ret;
> char *kernel_type;
> - struct filename *kernel_dir;
> char *kernel_dev;
> unsigned long data_page;
>
> @@ -2796,12 +2799,6 @@ SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
> if (IS_ERR(kernel_type))
> goto out_type;
>
> - kernel_dir = getname(dir_name);
> - if (IS_ERR(kernel_dir)) {
> - ret = PTR_ERR(kernel_dir);
> - goto out_dir;
> - }
> -
> kernel_dev = copy_mount_string(dev_name);
> ret = PTR_ERR(kernel_dev);
> if (IS_ERR(kernel_dev))
> @@ -2811,15 +2808,13 @@ SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
> if (ret < 0)
> goto out_data;
>
> - ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags,
> + ret = do_mount(kernel_dev, dir_name, kernel_type, flags,
> (void *) data_page);
>
> free_page(data_page);
> out_data:
> kfree(kernel_dev);
> out_dev:
> - putname(kernel_dir);
> -out_dir:
> kfree(kernel_type);
> out_type:
> return ret;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index bb2c58c..72cb93f 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1839,7 +1839,8 @@ extern struct vfsmount *kern_mount_data(struct file_system_type *, void *data);
> extern void kern_unmount(struct vfsmount *mnt);
> extern int may_umount_tree(struct vfsmount *);
> extern int may_umount(struct vfsmount *);
> -extern long do_mount(const char *, const char *, const char *, unsigned long, void *);
> +extern long do_mount(const char *, const char __user *,
> + const char *, unsigned long, void *);
> extern struct vfsmount *collect_mounts(struct path *);
> extern void drop_collected_mounts(struct vfsmount *);
> extern int iterate_mounts(int (*)(struct vfsmount *, void *), void *,

Looks sane.

Acked-by: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
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