[PATCH v7 7/9] coredump: validate socket name as it is written

[Alexander Mikhalitsyn]

Am Do., 15. Mai 2025 um 00:04 Uhr schrieb Christian Brauner
<brauner at kernel.org>:
>
> In contrast to other parameters written into
> /proc/sys/kernel/core_pattern that never fail we can validate enabling
> the new AF_UNIX support. This is obviously racy as hell but it's always
> been that way.
>
> Signed-off-by: Christian Brauner <brauner at kernel.org>

Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn at canonical.com>

> ---
>  fs/coredump.c | 37 ++++++++++++++++++++++++++++++++++---
>  1 file changed, 34 insertions(+), 3 deletions(-)
>
> diff --git a/fs/coredump.c b/fs/coredump.c
> index 6ee38e3da108..d4ff08ef03e5 100644
> --- a/fs/coredump.c
> +++ b/fs/coredump.c
> @@ -1228,13 +1228,44 @@ void validate_coredump_safety(void)
>         }
>  }
>
> +static inline bool check_coredump_socket(void)
> +{
> +       if (core_pattern[0] != '@')
> +               return true;
> +
> +       /*
> +        * Coredump socket must be located in the initial mount
> +        * namespace. Don't give the that impression anything else is
> +        * supported right now.
> +        */
> +       if (current->nsproxy->mnt_ns != init_task.nsproxy->mnt_ns)
> +               return false;
> +
> +       /* Must be an absolute path. */
> +       if (*(core_pattern + 1) != '/')
> +               return false;
> +
> +       return true;
> +}
> +
>  static int proc_dostring_coredump(const struct ctl_table *table, int write,
>                   void *buffer, size_t *lenp, loff_t *ppos)
>  {
> -       int error = proc_dostring(table, write, buffer, lenp, ppos);
> +       int error;
> +       ssize_t retval;
> +       char old_core_pattern[CORENAME_MAX_SIZE];
> +
> +       retval = strscpy(old_core_pattern, core_pattern, CORENAME_MAX_SIZE);
> +
> +       error = proc_dostring(table, write, buffer, lenp, ppos);
> +       if (error)
> +               return error;
> +       if (!check_coredump_socket()) {
> +               strscpy(core_pattern, old_core_pattern, retval + 1);
> +               return -EINVAL;
> +       }
>
> -       if (!error)
> -               validate_coredump_safety();
> +       validate_coredump_safety();
>         return error;
>  }
>
>
> --
> 2.47.2
>