Quoting Jean-Marc Pigeon (j...@safe.ca):
> Added syslog.c such container /proc/kmsg and host /proc/kmsg
> do not leak in each other.
> Running rsyslog daemon within a container won't destroy
> host kernel messages.
Thanks Jean-Marc. But this really isn't doing most of what I'd
recommended in my last emails (both public and private. In
particular:
> index cc4f453..3d0c73e 100644
> --- a/include/linux/user_namespace.h
> +++ b/include/linux/user_namespace.h
> @@ -14,6 +14,7 @@ struct user_namespace {
> struct hlist_head uidhash_table[UIDHASH_SZ];
> struct user_struct *creator;
> struct work_struct destroyer;
> + struct syslog_ns *syslog;
syslog_ns should be moved into nsproxy and unshared with a
separate clone(CLONE_SYSLOG);
> -static void emit_log_char(char c)
> +static void emit_log_char(struct syslog_ns *syslog_ns, char c)
> {
> - LOG_BUF(log_end) = c;
> - log_end++;
> - if (log_end - log_start > log_buf_len)
> - log_start = log_end - log_buf_len;
> - if (log_end - con_start > log_buf_len)
> - con_start = log_end - log_buf_len;
> - if (logged_chars < log_buf_len)
> - logged_chars++;
> + LOG_BUF(syslog_ns, sys_log_end) = c;
Taking syslog_ns from current in emit_log_char is not right.
Emit_log_char() is called from printk which (the comment above
printk warns us) can be called from any context.
That was why I suggested:
>! I think my patch is fundamentally wrong anyway: we should not
>! use current's context at vprintk like i did. We should use an
>! optional passed-in context from those callsites where we want to,
>! and default to init otherwise. That means
>!
>! 1. put the core of vprintk() into vnsprintk() which takes a syslog
>! namespace as argument
>!
>! 2. make vprintk() a wrapper around vnsprintk() which passes in
>! init_syslog_ns to vnsprintk(). printk can remain unchanged.
>!
>! 4. make nsprintk() a wrapper around vnsprintk() which takes a syslog
>! ns argument and pass it to vnsprintk()
>!
>! 3. do_syslog() can obviously be containerized the same way it
>! is now.
>!
>! 4. take a printk call like the iptables ones you want and turn
>! int into nsprintk syscall.
>!
>! The very comment above printk explains why I was an idiot to write
>! let alone send that patch.
thanks,
-serge
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