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SubjectRe: [PATCH] autofs - fix directory and symlink access
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On Fri, 2018-06-15 at 08:06 +0800, Ian Kent wrote:

Opps, missing Signed-off-by, please add it!

> Depending on how it is configured the autofs user space daemon can
> leave in use mounts mounted at exit and re-connect to them at start
> up. But for this to work best the state of the autofs file system
> needs to be left intact over the restart.
>
> Also, at system shutdown, mounts in an autofs file system might be
> umounted exposing a mount point trigger for which subsequent access
> can lead to a hang. So recent versions of automount(8) now does its
> best to set autofs file system mounts catatonic at shutdown.
>
> When autofs file system mounts are catatonic it's currently possible
> to create and remove directories and symlinks which can be a problem
> at restart, as described above.
>
> So return EACCES in the directory, symlink and unlink methods if the
> autofs file system is catatonic.

Signed-off-by: Ian Kent <raven@themaw.net>

> ---
> fs/autofs/root.c | 33 ++++++++++++++++++++++++++++++---
> 1 file changed, 30 insertions(+), 3 deletions(-)
>
> diff --git a/fs/autofs/root.c b/fs/autofs/root.c
> index a3d414150578..782e57b911ab 100644
> --- a/fs/autofs/root.c
> +++ b/fs/autofs/root.c
> @@ -559,6 +559,13 @@ static int autofs_dir_symlink(struct inode *dir,
> if (!autofs_oz_mode(sbi))
> return -EACCES;
>
> + /* autofs_oz_mode() needs to allow path walks when the
> + * autofs mount is catatonic but the state of an autofs
> + * file system needs to be preserved over restarts.
> + */
> + if (sbi->catatonic)
> + return -EACCES;
> +
> BUG_ON(!ino);
>
> autofs_clean_ino(ino);
> @@ -612,9 +619,15 @@ static int autofs_dir_unlink(struct inode *dir, struct
> dentry *dentry)
> struct autofs_info *ino = autofs_dentry_ino(dentry);
> struct autofs_info *p_ino;
>
> - /* This allows root to remove symlinks */
> - if (!autofs_oz_mode(sbi) && !capable(CAP_SYS_ADMIN))
> - return -EPERM;
> + if (!autofs_oz_mode(sbi))
> + return -EACCES;
> +
> + /* autofs_oz_mode() needs to allow path walks when the
> + * autofs mount is catatonic but the state of an autofs
> + * file system needs to be preserved over restarts.
> + */
> + if (sbi->catatonic)
> + return -EACCES;
>
> if (atomic_dec_and_test(&ino->count)) {
> p_ino = autofs_dentry_ino(dentry->d_parent);
> @@ -697,6 +710,13 @@ static int autofs_dir_rmdir(struct inode *dir, struct
> dentry *dentry)
> if (!autofs_oz_mode(sbi))
> return -EACCES;
>
> + /* autofs_oz_mode() needs to allow path walks when the
> + * autofs mount is catatonic but the state of an autofs
> + * file system needs to be preserved over restarts.
> + */
> + if (sbi->catatonic)
> + return -EACCES;
> +
> spin_lock(&sbi->lookup_lock);
> if (!simple_empty(dentry)) {
> spin_unlock(&sbi->lookup_lock);
> @@ -735,6 +755,13 @@ static int autofs_dir_mkdir(struct inode *dir,
> if (!autofs_oz_mode(sbi))
> return -EACCES;
>
> + /* autofs_oz_mode() needs to allow path walks when the
> + * autofs mount is catatonic but the state of an autofs
> + * file system needs to be preserved over restarts.
> + */
> + if (sbi->catatonic)
> + return -EACCES;
> +
> pr_debug("dentry %p, creating %pd\n", dentry, dentry);
>
> BUG_ON(!ino);
>
> --
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