panic: Introduce warn_limit

commit 9fc9e278a5c0b708eeffaf47d6eb0c82aa74ed78 upstream.

Like oops_limit, add warn_limit for limiting the number of warnings when
panic_on_warn is not set.

Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: tangmeng <tangmeng@uniontech.com>
Cc: "Guilherme G. Piccoli" <gpiccoli@igalia.com>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-doc@vger.kernel.org
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20221117234328.594699-5-keescook@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index 0d9b66f..b3588ff 100644 (file)
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -1532,6 +1532,16 @@ 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 disables checking
+the warning count. Setting this to 1 has the same effect as setting
+``panic_on_warn=1``. The default value is 0.
+
+
 watchdog
 ========
 

diff --git a/kernel/panic.c b/kernel/panic.c
index cfa3543..f4403fc 100644 (file)
--- 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;
 
 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) && warn_limit)
+               panic("%s: system warned too often (kernel.warn_limit is %d)",
+                     origin, warn_limit);
 }
 
 /**