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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id m68sm29730196pfm.85.2019.11.30.08.22.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 30 Nov 2019 08:22:59 -0800 (PST) Date: Sat, 30 Nov 2019 08:22:57 -0800 From: Kees Cook To: Konstantin Khlebnikov Cc: linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Sasha Levin , Greg Kroah-Hartman , rcu@vger.kernel.org, Tejun Heo , Andrew Morton , Linus Torvalds , Thomas Gleixner Subject: Re: [PATCH 1/2] kernel: set taint flag 'L' at any kind of lockup Message-ID: <201911300820.C587C6AC41@keescook> References: <157503370645.8187.6335564487789994134.stgit@buzz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <157503370645.8187.6335564487789994134.stgit@buzz> Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Fri, Nov 29, 2019 at 04:21:46PM +0300, Konstantin Khlebnikov wrote: > Any lockup or stall notifies about unexpected lack of progress. > It's better to know about them for further problem investigations. > > Right now only softlockup has own taint flag. Let's generalize it. > > This patch renames TAINT_SOFTLOCKUP into TAINT_LOCKUP at sets it for: > - softlockup > - hardlockup > - RCU stalls > - stuck in workqueues > - detected task hung This seems reasonable to me. The only nit I have is that it might be nicer to separate the rename from the new call sites, but if there's no v2, I'm fine with it this way. Reviewed-by: Kees Cook > > Signed-off-by: Konstantin Khlebnikov > --- > Documentation/admin-guide/sysctl/kernel.rst | 2 +- > Documentation/admin-guide/tainted-kernels.rst | 8 ++++++-- > include/linux/kernel.h | 2 +- > kernel/hung_task.c | 2 ++ > kernel/panic.c | 2 +- > kernel/rcu/tree_stall.h | 1 + > kernel/watchdog.c | 2 +- > kernel/watchdog_hld.c | 1 + > kernel/workqueue.c | 1 + > tools/debugging/kernel-chktaint | 2 +- > 10 files changed, 16 insertions(+), 7 deletions(-) > > diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst > index 032c7cd3cede..60867ec525a4 100644 > --- a/Documentation/admin-guide/sysctl/kernel.rst > +++ b/Documentation/admin-guide/sysctl/kernel.rst > @@ -1082,7 +1082,7 @@ ORed together. The letters are seen in "Tainted" line of Oops reports. > 2048 `(I)` workaround for bug in platform firmware applied > 4096 `(O)` externally-built ("out-of-tree") module was loaded > 8192 `(E)` unsigned module was loaded > - 16384 `(L)` soft lockup occurred > + 16384 `(L)` lockup occurred > 32768 `(K)` kernel has been live patched > 65536 `(X)` Auxiliary taint, defined and used by for distros > 131072 `(T)` The kernel was built with the struct randomization plugin > diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst > index 71e9184a9079..fc76d0aad9f5 100644 > --- a/Documentation/admin-guide/tainted-kernels.rst > +++ b/Documentation/admin-guide/tainted-kernels.rst > @@ -96,7 +96,7 @@ Bit Log Number Reason that got the kernel tainted > 11 _/I 2048 workaround for bug in platform firmware applied > 12 _/O 4096 externally-built ("out-of-tree") module was loaded > 13 _/E 8192 unsigned module was loaded > - 14 _/L 16384 soft lockup occurred > + 14 _/L 16384 lockup occurred > 15 _/K 32768 kernel has been live patched > 16 _/X 65536 auxiliary taint, defined for and used by distros > 17 _/T 131072 kernel was built with the struct randomization plugin > @@ -152,7 +152,11 @@ More detailed explanation for tainting > 13) ``E`` if an unsigned module has been loaded in a kernel supporting > module signature. > > - 14) ``L`` if a soft lockup has previously occurred on the system. > + 14) ``L`` if some kind of lockup has previously occurred on the system: > + - soft/hardlockup, see Documentation/admin-guide/lockup-watchdogs.rst > + - RCU stall, see Documentation/RCU/stallwarn.txt > + - hung task detected, see CONFIG_DETECT_HUNG_TASK > + - kernel workqueue lockup, see CONFIG_WQ_WATCHDOG > > 15) ``K`` if the kernel has been live patched. > > diff --git a/include/linux/kernel.h b/include/linux/kernel.h > index d83d403dac2e..e8a6808e4f2f 100644 > --- a/include/linux/kernel.h > +++ b/include/linux/kernel.h > @@ -591,7 +591,7 @@ extern enum system_states { > #define TAINT_FIRMWARE_WORKAROUND 11 > #define TAINT_OOT_MODULE 12 > #define TAINT_UNSIGNED_MODULE 13 > -#define TAINT_SOFTLOCKUP 14 > +#define TAINT_LOCKUP 14 > #define TAINT_LIVEPATCH 15 > #define TAINT_AUX 16 > #define TAINT_RANDSTRUCT 17 > diff --git a/kernel/hung_task.c b/kernel/hung_task.c > index 14a625c16cb3..521eb2fbf5fc 100644 > --- a/kernel/hung_task.c > +++ b/kernel/hung_task.c > @@ -139,6 +139,8 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) > hung_task_show_lock = true; > } > > + add_taint(TAINT_LOCKUP, LOCKDEP_STILL_OK); > + > touch_nmi_watchdog(); > } > > diff --git a/kernel/panic.c b/kernel/panic.c > index f470a038b05b..d7750a45ca8d 100644 > --- a/kernel/panic.c > +++ b/kernel/panic.c > @@ -372,7 +372,7 @@ const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = { > [ TAINT_FIRMWARE_WORKAROUND ] = { 'I', ' ', false }, > [ TAINT_OOT_MODULE ] = { 'O', ' ', true }, > [ TAINT_UNSIGNED_MODULE ] = { 'E', ' ', true }, > - [ TAINT_SOFTLOCKUP ] = { 'L', ' ', false }, > + [ TAINT_LOCKUP ] = { 'L', ' ', false }, > [ TAINT_LIVEPATCH ] = { 'K', ' ', true }, > [ TAINT_AUX ] = { 'X', ' ', true }, > [ TAINT_RANDSTRUCT ] = { 'T', ' ', true }, > diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h > index c0b8c458d8a6..181495efff80 100644 > --- a/kernel/rcu/tree_stall.h > +++ b/kernel/rcu/tree_stall.h > @@ -74,6 +74,7 @@ early_initcall(check_cpu_stall_init); > /* If so specified via sysctl, panic, yielding cleaner stall-warning output. */ > static void panic_on_rcu_stall(void) > { > + add_taint(TAINT_LOCKUP, LOCKDEP_STILL_OK); > if (sysctl_panic_on_rcu_stall) > panic("RCU Stall\n"); > } > diff --git a/kernel/watchdog.c b/kernel/watchdog.c > index f41334ef0971..d60b195708f7 100644 > --- a/kernel/watchdog.c > +++ b/kernel/watchdog.c > @@ -466,7 +466,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) > smp_mb__after_atomic(); > } > > - add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK); > + add_taint(TAINT_LOCKUP, LOCKDEP_STILL_OK); > if (softlockup_panic) > panic("softlockup: hung tasks"); > __this_cpu_write(soft_watchdog_warn, true); > diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c > index 247bf0b1582c..f77256f47422 100644 > --- a/kernel/watchdog_hld.c > +++ b/kernel/watchdog_hld.c > @@ -152,6 +152,7 @@ static void watchdog_overflow_callback(struct perf_event *event, > !test_and_set_bit(0, &hardlockup_allcpu_dumped)) > trigger_allbutself_cpu_backtrace(); > > + add_taint(TAINT_LOCKUP, LOCKDEP_STILL_OK); > if (hardlockup_panic) > nmi_panic(regs, "Hard LOCKUP"); > > diff --git a/kernel/workqueue.c b/kernel/workqueue.c > index bc2e09a8ea61..825a92893882 100644 > --- a/kernel/workqueue.c > +++ b/kernel/workqueue.c > @@ -5741,6 +5741,7 @@ static void wq_watchdog_timer_fn(struct timer_list *unused) > pr_cont_pool_info(pool); > pr_cont(" stuck for %us!\n", > jiffies_to_msecs(jiffies - pool_ts) / 1000); > + add_taint(TAINT_LOCKUP, LOCKDEP_STILL_OK); > } > } > > diff --git a/tools/debugging/kernel-chktaint b/tools/debugging/kernel-chktaint > index 2240cb56e6e5..9f24719d8c80 100755 > --- a/tools/debugging/kernel-chktaint > +++ b/tools/debugging/kernel-chktaint > @@ -168,7 +168,7 @@ if [ `expr $T % 2` -eq 0 ]; then > addout " " > else > addout "L" > - echo " * soft lockup occurred (#14)" > + echo " * lockup occurred (#14)" > fi > > T=`expr $T / 2` > -- Kees Cook