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

Alexander Mikhalitsyn
2025-05-15T14:04:03Z

Am Do., 15. Mai 2025 um 00:04 Uhr schrieb Christian Brauner
<brauner@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@kernel.org>

Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@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
>