On Sun, Apr 16, 2023 at 06:38:19PM +0000, Stephen J. Kiernan wrote:
> The branch main has been updated by stevek:
>
> URL:
> https://cgit.FreeBSD.org/src/commit/?id=4819e5aeda4ef1a193a08e29b4099c3c30369a81
>
> commit 4819e5aeda4ef1a193a08e29b4099c3c30369a81
> Author: Stephen J. Kiernan <[email protected]>
> AuthorDate: 2023-04-16 03:59:52 +0000
> Commit: Stephen J. Kiernan <[email protected]>
> CommitDate: 2023-04-16 18:37:58 +0000
>
> Add new privilege PRIV_KDB_SET_BACKEND
>
> Summary:
> Check for PRIV_KDB_SET_BACKEND before allowing a thread to change
> the KDB backend.
>
> Obtained from: Juniper Networks, Inc.
> Reviewers: sjg, emaste
> Subscribers: imp
>
> Differential Revision: https://reviews.freebsd.org/D39538
> ---
> sys/kern/subr_kdb.c | 6 ++++++
> sys/sys/priv.h | 7 ++++++-
> 2 files changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/sys/kern/subr_kdb.c b/sys/kern/subr_kdb.c
> index ff981cdfe47c..8aae19b728c8 100644
> --- a/sys/kern/subr_kdb.c
> +++ b/sys/kern/subr_kdb.c
> @@ -40,6 +40,7 @@ __FBSDID("$FreeBSD$");
> #include <sys/malloc.h>
> #include <sys/lock.h>
> #include <sys/pcpu.h>
> +#include <sys/priv.h>
> #include <sys/proc.h>
> #include <sys/sbuf.h>
> #include <sys/smp.h>
> @@ -484,6 +485,11 @@ int
> kdb_dbbe_select(const char *name)
> {
> struct kdb_dbbe *be, **iter;
> + int error;
> +
> + error = priv_check(curthread, PRIV_KDB_SET_BACKEND);
priv_check() fails for jailed, or even simply non-root process.
kdb_dbbe_select() is called from a random context, e.g. from
kdb_alt_break_gdb(), where it inherits whatever thread was running
at the moment of break to debugger.
In other words, this function no longer works reliably.
> + if (error)
> + return (error);
>
> SET_FOREACH(iter, kdb_dbbe_set) {
> be = *iter;
> diff --git a/sys/sys/priv.h b/sys/sys/priv.h
> index 20bfc7312ce3..cb4dcecea4aa 100644
> --- a/sys/sys/priv.h
> +++ b/sys/sys/priv.h
> @@ -515,10 +515,15 @@
> #define PRIV_KMEM_READ 680 /* Open mem/kmem for reading. */
> #define PRIV_KMEM_WRITE 681 /* Open mem/kmem for writing. */
>
> +/*
> + * Kernel debugger privileges.
> + */
> +#define PRIV_KDB_SET_BACKEND 690 /* Allow setting KDB backend. */
> +
> /*
> * Track end of privilege list.
> */
> -#define _PRIV_HIGHEST 682
> +#define _PRIV_HIGHEST 691
>
> /*
> * Validate that a named privilege is known by the privilege system. Invalid
