[v3,0/6] exit: Put an upper limit on how often we can oops

Message

Kees Cook Nov. 17, 2022, 11:43 p.m. UTC

Hi,

This builds on Jann's v1 patch[1]. Changes in v3:
- fix #if/#ifdef confusion (Bill)
- rename from "reason" or "origin" and add it to the warn output (Marco)

v2: https://lore.kernel.org/lkml/[e-mail]/

Thanks,

-Kees

[1] https://lore.kernel.org/lkml/[e-mail]

Jann Horn (1):
  exit: Put an upper limit on how often we can oops

Kees Cook (5):
  panic: Separate sysctl logic from CONFIG_SMP
  exit: Expose "oops_count" to sysfs
  panic: Consolidate open-coded panic_on_warn checks
  panic: Introduce warn_limit
  panic: Expose "warn_count" to sysfs

 .../ABI/testing/sysfs-kernel-oops_count       |  6 ++
 .../ABI/testing/sysfs-kernel-warn_count       |  6 ++
 Documentation/admin-guide/sysctl/kernel.rst   | 17 ++++++
 MAINTAINERS                                   |  2 +
 include/linux/panic.h                         |  1 +
 kernel/exit.c                                 | 60 +++++++++++++++++++
 kernel/kcsan/report.c                         |  3 +-
 kernel/panic.c                                | 45 +++++++++++++-
 kernel/sched/core.c                           |  3 +-
 lib/ubsan.c                                   |  3 +-
 mm/kasan/report.c                             |  4 +-
 mm/kfence/report.c                            |  3 +-
 12 files changed, 140 insertions(+), 13 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-kernel-oops_count
 create mode 100644 Documentation/ABI/testing/sysfs-kernel-warn_count

Comments

Kees Cook Nov. 18, 2022, 12:27 a.m. UTC | #1

On Thu, Nov 17, 2022 at 03:43:25PM -0800, Kees Cook wrote:
> Like oops_limit, add warn_limit for limiting the number of warnings when
> panic_on_warn is not set.
> 
> Cc: Jonathan Corbet <[e-mail]>
> Cc: Andrew Morton <[e-mail]>
> Cc: Baolin Wang <[e-mail]>
> Cc: "Jason A. Donenfeld" <[e-mail]>
> Cc: Eric Biggers <[e-mail]>
> Cc: Huang Ying <[e-mail]>
> Cc: Petr Mladek <[e-mail]>
> Cc: tangmeng <[e-mail]>
> Cc: "Guilherme G. Piccoli" <[e-mail]>
> Cc: Tiezhu Yang <[e-mail]>
> Cc: Sebastian Andrzej Siewior <[e-mail]>
> Cc: [e-mail]
> Reviewed-by: Luis Chamberlain <[e-mail]>
> Signed-off-by: Kees Cook <[e-mail]>
> ---
>  Documentation/admin-guide/sysctl/kernel.rst |  9 +++++++++
>  kernel/panic.c                              | 14 ++++++++++++++
>  2 files changed, 23 insertions(+)
> 
> diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
> index 09f3fb2f8585..c385d5319cdf 100644
> --- a/Documentation/admin-guide/sysctl/kernel.rst
> +++ b/Documentation/admin-guide/sysctl/kernel.rst
> @@ -1508,6 +1508,15 @@ entry will default to 2 instead of 0.
>  2 Unprivileged calls to ``bpf()`` are disabled
>  = =============================================================
>  
> +
> +warn_limit
> +==========
> +
> +Number of kernel warnings after which the kernel should panic when
> +``panic_on_warn`` is not set. Setting this to 0 or 1 has the same effect
> +as setting ``panic_on_warn=1``.
> +
> +
>  watchdog
>  ========
>  
> diff --git a/kernel/panic.c b/kernel/panic.c
> index cfa354322d5f..e5aab27496d7 100644
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -58,6 +58,7 @@ bool crash_kexec_post_notifiers;
>  int panic_on_warn __read_mostly;
>  unsigned long panic_on_taint;
>  bool panic_on_taint_nousertaint = false;
> +static unsigned int warn_limit __read_mostly = 10000;
>  
>  int panic_timeout = CONFIG_PANIC_TIMEOUT;
>  EXPORT_SYMBOL_GPL(panic_timeout);
> @@ -88,6 +89,13 @@ static struct ctl_table kern_panic_table[] = {
>  		.extra2         = SYSCTL_ONE,
>  	},
>  #endif
> +	{
> +		.procname       = "warn_limit",
> +		.data           = &warn_limit,
> +		.maxlen         = sizeof(warn_limit),
> +		.mode           = 0644,
> +		.proc_handler   = proc_douintvec,
> +	},
>  	{ }
>  };
>  
> @@ -203,8 +211,14 @@ static void panic_print_sys_info(bool console_flush)
>  
>  void check_panic_on_warn(const char *origin)
>  {
> +	static atomic_t warn_count = ATOMIC_INIT(0);
> +
>  	if (panic_on_warn)
>  		panic("%s: panic_on_warn set ...\n", origin);
> +
> +	if (atomic_inc_return(&warn_count) >= READ_ONCE(warn_limit))
> +		panic("%s: system warned too often (kernel.warn_limit is %d)",
> +		      warn_limit);

Bah. This should be:  origin, warn_limit.