From 9360d035a579d95d1e76c471061b9065b18a0eb1 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Thu, 17 Nov 2022 15:43:21 -0800 Subject: panic: Separate sysctl logic from CONFIG_SMP In preparation for adding more sysctls directly in kernel/panic.c, split CONFIG_SMP from the logic that adds sysctls. Cc: Petr Mladek Cc: Andrew Morton Cc: tangmeng Cc: "Guilherme G. Piccoli" Cc: Tiezhu Yang Cc: Sebastian Andrzej Siewior Reviewed-by: Luis Chamberlain Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20221117234328.594699-1-keescook@chromium.org --- kernel/panic.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'kernel/panic.c') diff --git a/kernel/panic.c b/kernel/panic.c index da323209f583..d843d036651e 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -75,8 +75,9 @@ ATOMIC_NOTIFIER_HEAD(panic_notifier_list); EXPORT_SYMBOL(panic_notifier_list); -#if defined(CONFIG_SMP) && defined(CONFIG_SYSCTL) +#ifdef CONFIG_SYSCTL static struct ctl_table kern_panic_table[] = { +#ifdef CONFIG_SMP { .procname = "oops_all_cpu_backtrace", .data = &sysctl_oops_all_cpu_backtrace, @@ -86,6 +87,7 @@ static struct ctl_table kern_panic_table[] = { .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_ONE, }, +#endif { } }; -- cgit v1.2.3 From 79cc1ba7badf9e7a12af99695a557e9ce27ee967 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Thu, 17 Nov 2022 15:43:24 -0800 Subject: panic: Consolidate open-coded panic_on_warn checks Several run-time checkers (KASAN, UBSAN, KFENCE, KCSAN, sched) roll their own warnings, and each check "panic_on_warn". Consolidate this into a single function so that future instrumentation can be added in a single location. Cc: Marco Elver Cc: Dmitry Vyukov Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Steven Rostedt Cc: Ben Segall Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Valentin Schneider Cc: Andrey Ryabinin Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Vincenzo Frascino Cc: Andrew Morton Cc: David Gow Cc: tangmeng Cc: Jann Horn Cc: Shuah Khan Cc: Petr Mladek Cc: "Paul E. McKenney" Cc: Sebastian Andrzej Siewior Cc: "Guilherme G. Piccoli" Cc: Tiezhu Yang Cc: kasan-dev@googlegroups.com Cc: linux-mm@kvack.org Reviewed-by: Luis Chamberlain Signed-off-by: Kees Cook Reviewed-by: Marco Elver Reviewed-by: Andrey Konovalov Link: https://lore.kernel.org/r/20221117234328.594699-4-keescook@chromium.org --- include/linux/panic.h | 1 + kernel/kcsan/report.c | 3 +-- kernel/panic.c | 9 +++++++-- kernel/sched/core.c | 3 +-- lib/ubsan.c | 3 +-- mm/kasan/report.c | 4 ++-- mm/kfence/report.c | 3 +-- 7 files changed, 14 insertions(+), 12 deletions(-) (limited to 'kernel/panic.c') diff --git a/include/linux/panic.h b/include/linux/panic.h index c7759b3f2045..979b776e3bcb 100644 --- a/include/linux/panic.h +++ b/include/linux/panic.h @@ -11,6 +11,7 @@ extern long (*panic_blink)(int state); __printf(1, 2) void panic(const char *fmt, ...) __noreturn __cold; void nmi_panic(struct pt_regs *regs, const char *msg); +void check_panic_on_warn(const char *origin); extern void oops_enter(void); extern void oops_exit(void); extern bool oops_may_print(void); diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c index 67794404042a..e95ce7d7a76e 100644 --- a/kernel/kcsan/report.c +++ b/kernel/kcsan/report.c @@ -492,8 +492,7 @@ static void print_report(enum kcsan_value_change value_change, dump_stack_print_info(KERN_DEFAULT); pr_err("==================================================================\n"); - if (panic_on_warn) - panic("panic_on_warn set ...\n"); + check_panic_on_warn("KCSAN"); } static void release_report(unsigned long *flags, struct other_info *other_info) diff --git a/kernel/panic.c b/kernel/panic.c index d843d036651e..cfa354322d5f 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -201,6 +201,12 @@ static void panic_print_sys_info(bool console_flush) ftrace_dump(DUMP_ALL); } +void check_panic_on_warn(const char *origin) +{ + if (panic_on_warn) + panic("%s: panic_on_warn set ...\n", origin); +} + /** * panic - halt the system * @fmt: The text string to print @@ -619,8 +625,7 @@ void __warn(const char *file, int line, void *caller, unsigned taint, if (regs) show_regs(regs); - if (panic_on_warn) - panic("panic_on_warn set ...\n"); + check_panic_on_warn("kernel"); if (!regs) dump_stack(); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 5800b0623ff3..285ef8821b4f 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5729,8 +5729,7 @@ static noinline void __schedule_bug(struct task_struct *prev) pr_err("Preemption disabled at:"); print_ip_sym(KERN_ERR, preempt_disable_ip); } - if (panic_on_warn) - panic("scheduling while atomic\n"); + check_panic_on_warn("scheduling while atomic"); dump_stack(); add_taint(TAINT_WARN, LOCKDEP_STILL_OK); diff --git a/lib/ubsan.c b/lib/ubsan.c index 36bd75e33426..60c7099857a0 100644 --- a/lib/ubsan.c +++ b/lib/ubsan.c @@ -154,8 +154,7 @@ static void ubsan_epilogue(void) current->in_ubsan--; - if (panic_on_warn) - panic("panic_on_warn set ...\n"); + check_panic_on_warn("UBSAN"); } void __ubsan_handle_divrem_overflow(void *_data, void *lhs, void *rhs) diff --git a/mm/kasan/report.c b/mm/kasan/report.c index df3602062bfd..cc98dfdd3ed2 100644 --- a/mm/kasan/report.c +++ b/mm/kasan/report.c @@ -164,8 +164,8 @@ static void end_report(unsigned long *flags, void *addr) (unsigned long)addr); pr_err("==================================================================\n"); spin_unlock_irqrestore(&report_lock, *flags); - if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) - panic("panic_on_warn set ...\n"); + if (!test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) + check_panic_on_warn("KASAN"); if (kasan_arg_fault == KASAN_ARG_FAULT_PANIC) panic("kasan.fault=panic set ...\n"); add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); diff --git a/mm/kfence/report.c b/mm/kfence/report.c index 7e496856c2eb..110c27ca597d 100644 --- a/mm/kfence/report.c +++ b/mm/kfence/report.c @@ -268,8 +268,7 @@ void kfence_report_error(unsigned long address, bool is_write, struct pt_regs *r lockdep_on(); - if (panic_on_warn) - panic("panic_on_warn set ...\n"); + check_panic_on_warn("KFENCE"); /* We encountered a memory safety error, taint the kernel! */ add_taint(TAINT_BAD_PAGE, LOCKDEP_STILL_OK); -- cgit v1.2.3 From 9fc9e278a5c0b708eeffaf47d6eb0c82aa74ed78 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Thu, 17 Nov 2022 15:43:25 -0800 Subject: panic: Introduce warn_limit Like oops_limit, add warn_limit for limiting the number of warnings when panic_on_warn is not set. Cc: Jonathan Corbet Cc: Andrew Morton Cc: Baolin Wang Cc: "Jason A. Donenfeld" Cc: Eric Biggers Cc: Huang Ying Cc: Petr Mladek Cc: tangmeng Cc: "Guilherme G. Piccoli" Cc: Tiezhu Yang Cc: Sebastian Andrzej Siewior Cc: linux-doc@vger.kernel.org Reviewed-by: Luis Chamberlain Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20221117234328.594699-5-keescook@chromium.org --- Documentation/admin-guide/sysctl/kernel.rst | 10 ++++++++++ kernel/panic.c | 14 ++++++++++++++ 2 files changed, 24 insertions(+) (limited to 'kernel/panic.c') diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index a31d8d81ea07..179bd303b585 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -1509,6 +1509,16 @@ 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 cfa354322d5f..f4403fc14f67 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; 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); } /** -- cgit v1.2.3 From 8b05aa26336113c4cea25f1c333ee8cd4fc212a6 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Thu, 17 Nov 2022 15:43:26 -0800 Subject: panic: Expose "warn_count" to sysfs Since Warn count is now tracked and is a fairly interesting signal, add the entry /sys/kernel/warn_count to expose it to userspace. Cc: Petr Mladek Cc: Andrew Morton Cc: tangmeng Cc: "Guilherme G. Piccoli" Cc: Sebastian Andrzej Siewior Cc: Tiezhu Yang Reviewed-by: Luis Chamberlain Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20221117234328.594699-6-keescook@chromium.org --- Documentation/ABI/testing/sysfs-kernel-warn_count | 6 ++++++ MAINTAINERS | 1 + kernel/panic.c | 22 ++++++++++++++++++++-- 3 files changed, 27 insertions(+), 2 deletions(-) create mode 100644 Documentation/ABI/testing/sysfs-kernel-warn_count (limited to 'kernel/panic.c') diff --git a/Documentation/ABI/testing/sysfs-kernel-warn_count b/Documentation/ABI/testing/sysfs-kernel-warn_count new file mode 100644 index 000000000000..08f083d2fd51 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-kernel-warn_count @@ -0,0 +1,6 @@ +What: /sys/kernel/oops_count +Date: November 2022 +KernelVersion: 6.2.0 +Contact: Linux Kernel Hardening List +Description: + Shows how many times the system has Warned since last boot. diff --git a/MAINTAINERS b/MAINTAINERS index 0a1e95a58e54..282cd8a513fd 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -11107,6 +11107,7 @@ L: linux-hardening@vger.kernel.org S: Supported T: git git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/hardening F: Documentation/ABI/testing/sysfs-kernel-oops_count +F: Documentation/ABI/testing/sysfs-kernel-warn_count F: include/linux/overflow.h F: include/linux/randomize_kstack.h F: mm/usercopy.c diff --git a/kernel/panic.c b/kernel/panic.c index f4403fc14f67..54deb743b2d5 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -32,6 +32,7 @@ #include #include #include +#include #include #include @@ -107,6 +108,25 @@ static __init int kernel_panic_sysctls_init(void) late_initcall(kernel_panic_sysctls_init); #endif +static atomic_t warn_count = ATOMIC_INIT(0); + +#ifdef CONFIG_SYSFS +static ssize_t warn_count_show(struct kobject *kobj, struct kobj_attribute *attr, + char *page) +{ + return sysfs_emit(page, "%d\n", atomic_read(&warn_count)); +} + +static struct kobj_attribute warn_count_attr = __ATTR_RO(warn_count); + +static __init int kernel_panic_sysfs_init(void) +{ + sysfs_add_file_to_group(kernel_kobj, &warn_count_attr.attr, NULL); + return 0; +} +late_initcall(kernel_panic_sysfs_init); +#endif + static long no_blink(int state) { return 0; @@ -211,8 +231,6 @@ 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); -- cgit v1.2.3