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Jonathan Lemon 69ca310f34 bpf: Save correct stopping point in file seq iteration 
On some systems, some variant of the following splat is
repeatedly seen.  The common factor in all traces seems
to be the entry point to task_file_seq_next().  With the
patch, all warnings go away.

    rcu: INFO: rcu_sched self-detected stall on CPU
    rcu: \x0926-....: (20992 ticks this GP) idle=d7e/1/0x4000000000000002 softirq=81556231/81556231 fqs=4876
    \x09(t=21033 jiffies g=159148529 q=223125)
    NMI backtrace for cpu 26
    CPU: 26 PID: 2015853 Comm: bpftool Kdump: loaded Not tainted 5.6.13-0_fbk4_3876_gd8d1f9bf80bb #1
    Hardware name: Quanta Twin Lakes MP/Twin Lakes Passive MP, BIOS F09_3A12 10/08/2018
    Call Trace:
     <IRQ>
     dump_stack+0x50/0x70
     nmi_cpu_backtrace.cold.6+0x13/0x50
     ? lapic_can_unplug_cpu.cold.30+0x40/0x40
     nmi_trigger_cpumask_backtrace+0xba/0xca
     rcu_dump_cpu_stacks+0x99/0xc7
     rcu_sched_clock_irq.cold.90+0x1b4/0x3aa
     ? tick_sched_do_timer+0x60/0x60
     update_process_times+0x24/0x50
     tick_sched_timer+0x37/0x70
     __hrtimer_run_queues+0xfe/0x270
     hrtimer_interrupt+0xf4/0x210
     smp_apic_timer_interrupt+0x5e/0x120
     apic_timer_interrupt+0xf/0x20
     </IRQ>
    RIP: 0010:get_pid_task+0x38/0x80
    Code: 89 f6 48 8d 44 f7 08 48 8b 00 48 85 c0 74 2b 48 83 c6 55 48 c1 e6 04 48 29 f0 74 19 48 8d 78 20 ba 01 00 00 00 f0 0f c1 50 20 <85> d2 74 27 78 11 83 c2 01 78 0c 48 83 c4 08 c3 31 c0 48 83 c4 08
    RSP: 0018:ffffc9000d293dc8 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff13
    RAX: ffff888637c05600 RBX: ffffc9000d293e0c RCX: 0000000000000000
    RDX: 0000000000000001 RSI: 0000000000000550 RDI: ffff888637c05620
    RBP: ffffffff8284eb80 R08: ffff88831341d300 R09: ffff88822ffd8248
    R10: ffff88822ffd82d0 R11: 00000000003a93c0 R12: 0000000000000001
    R13: 00000000ffffffff R14: ffff88831341d300 R15: 0000000000000000
     ? find_ge_pid+0x1b/0x20
     task_seq_get_next+0x52/0xc0
     task_file_seq_get_next+0x159/0x220
     task_file_seq_next+0x4f/0xa0
     bpf_seq_read+0x159/0x390
     vfs_read+0x8a/0x140
     ksys_read+0x59/0xd0
     do_syscall_64+0x42/0x110
     entry_SYSCALL_64_after_hwframe+0x44/0xa9
    RIP: 0033:0x7f95ae73e76e
    Code: Bad RIP value.
    RSP: 002b:00007ffc02c1dbf8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
    RAX: ffffffffffffffda RBX: 000000000170faa0 RCX: 00007f95ae73e76e
    RDX: 0000000000001000 RSI: 00007ffc02c1dc30 RDI: 0000000000000007
    RBP: 00007ffc02c1ec70 R08: 0000000000000005 R09: 0000000000000006
    R10: fffffffffffff20b R11: 0000000000000246 R12: 00000000019112a0
    R13: 0000000000000000 R14: 0000000000000007 R15: 00000000004283c0

If unable to obtain the file structure for the current task,
proceed to the next task number after the one returned from
task_seq_get_next(), instead of the next task number from the
original iterator.

Also, save the stopping task number from task_seq_get_next()
on failure in case of restarts.

Fixes: eaaacd2391 ("bpf: Add task and task/file iterator targets")
Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20201218185032.2464558-2-jonathan.lemon@gmail.com
2020-12-24 02:04:47 +01:00
..
bpf bpf: Save correct stopping point in file seq iteration 2020-12-24 02:04:47 +01:00
cgroup Merge branch 'akpm' (patches from Andrew) 2020-12-15 12:53:37 -08:00
configs
debug smp: Cleanup smp_call_function*() 2020-11-24 16:47:49 +01:00
dma swiotlb: remove the tbl_dma_addr argument to swiotlb_tbl_map_single 2020-11-02 10:10:39 -05:00
entry The new preemtible kmap_local() implementation: 2020-12-14 18:35:53 -08:00
events Perf updates: 2020-12-14 17:34:12 -08:00
gcov gcov: add support for GCC 10.1 2020-09-11 09:33:54 -07:00
irq Driver core updates for 5.11-rc1 2020-12-15 14:02:26 -08:00
kcsan kcsan: Fix encoding masks and regain address bit 2020-11-06 17:19:26 -08:00
livepatch kernel/: fix repeated words in comments 2020-10-16 11:11:19 -07:00
locking A moderate set of locking updates: 2020-12-14 17:27:47 -08:00
power kernel/power: allow hibernation with page_poison sanity checking 2020-12-15 12:13:46 -08:00
printk Scheduler updates: 2020-12-14 18:29:11 -08:00
rcu Scheduler updates: 2020-12-14 18:29:11 -08:00
sched The new preemtible kmap_local() implementation: 2020-12-14 18:35:53 -08:00
time Scheduler updates: 2020-12-14 18:29:11 -08:00
trace Networking updates for 5.11 2020-12-15 13:22:29 -08:00
.gitignore
acct.c kernel: acct.c: fix some kernel-doc nits 2020-10-16 11:11:19 -07:00
async.c treewide: Remove uninitialized_var() usage 2020-07-16 12:35:15 -07:00
audit_fsnotify.c fsnotify: create method handle_inode_event() in fsnotify_operations 2020-07-27 23:25:50 +02:00
audit_tree.c \n 2020-08-06 19:29:51 -07:00
audit_watch.c fsnotify: create method handle_inode_event() in fsnotify_operations 2020-07-27 23:25:50 +02:00
audit.c audit: Remove redundant null check 2020-08-26 09:10:39 -04:00
audit.h audit: change unnecessary globals into statics 2020-08-17 20:26:58 -04:00
auditfilter.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
auditsc.c audit: Migrate to use SYSCALL_WORK flag 2020-11-16 21:53:16 +01:00
backtracetest.c treewide: Replace DECLARE_TASKLET() with DECLARE_TASKLET_OLD() 2020-07-30 11:15:58 -07:00
bounds.c
capability.c LSM: Signal to SafeSetID when setting group IDs 2020-10-13 09:17:34 -07:00
compat.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
configs.c
context_tracking.c context_tracking: Ensure that the critical path cannot be instrumented 2020-06-11 15:14:36 +02:00
cpu_pm.c notifier: Fix broken error handling pattern 2020-09-01 09:58:03 +02:00
cpu.c Scheduler updates: 2020-12-14 18:29:11 -08:00
crash_core.c crypto: sha - split sha.h into sha1.h and sha2.h 2020-11-20 14:45:33 +11:00
crash_dump.c
cred.c
delayacct.c
dma.c
exec_domain.c
exit.c Merge branch 'linus' into sched/core, to resolve semantic conflict 2020-11-27 11:10:50 +01:00
extable.c
fail_function.c fail_function: Remove a redundant mutex unlock 2020-11-19 11:58:16 -08:00
fork.c Networking updates for 5.11 2020-12-15 13:22:29 -08:00
freezer.c
futex.c Merge branch 'locking/rwsem' 2020-12-09 17:08:45 +01:00
gen_kheaders.sh kbuild: add variables for compression tools 2020-06-06 23:42:01 +09:00
groups.c LSM: Signal to SafeSetID when setting group IDs 2020-10-13 09:17:34 -07:00
hung_task.c kernel/hung_task.c: make type annotations consistent 2020-11-02 12:14:19 -08:00
iomem.c
irq_work.c irq_work: Optimize irq_work_single() 2020-11-24 16:47:49 +01:00
jump_label.c kernel/: fix repeated words in comments 2020-10-16 11:11:19 -07:00
kallsyms.c treewide: Convert macro and uses of __section(foo) to __section("foo") 2020-10-25 14:51:49 -07:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c kernel: make kcov_common_handle consider the current context 2020-11-02 18:00:20 -08:00
kexec_core.c crypto: sha - split sha.h into sha1.h and sha2.h 2020-11-20 14:45:33 +11:00
kexec_elf.c
kexec_file.c crypto: sha - split sha.h into sha1.h and sha2.h 2020-11-20 14:45:33 +11:00
kexec_internal.h
kexec.c LSM: Introduce kernel_post_load_data() hook 2020-10-05 13:37:03 +02:00
kheaders.c
kmod.c kmod: remove redundant "be an" in the comment 2020-08-12 10:58:01 -07:00
kprobes.c Merge branch 'linus' into perf/kprobes 2020-11-07 13:18:49 +01:00
ksysfs.c
kthread.c Merge branch 'akpm' (patches from Andrew) 2020-12-15 12:53:37 -08:00
latencytop.c
Makefile elfcore: fix building with clang 2020-12-11 14:02:14 -08:00
module_signature.c
module_signing.c
module-internal.h
module.c bpf: Keep module's btf_data_size intact after load 2020-12-03 17:38:20 -08:00
notifier.c notifier: Fix broken error handling pattern 2020-09-01 09:58:03 +02:00
nsproxy.c fixes-v5.11 2020-12-14 16:40:27 -08:00
padata.c padata: fix possible padata_works_lock deadlock 2020-09-04 17:51:55 +10:00
panic.c panic: don't dump stack twice on warn 2020-11-14 11:26:04 -08:00
params.c params: Replace zero-length array with flexible-array member 2020-10-29 17:22:59 -05:00
pid_namespace.c fixes-v5.11 2020-12-14 16:40:27 -08:00
pid.c fixes-v5.11 2020-12-14 16:40:27 -08:00
profile.c
ptrace.c Merge branch 'akpm' (patches from Andrew) 2020-12-15 12:53:37 -08:00
range.c kernel.h: split out min()/max() et al. helpers 2020-10-16 11:11:19 -07:00
reboot.c reboot: fix overflow parsing reboot cpu number 2020-11-14 11:26:03 -08:00
regset.c regset: kill ->get() 2020-07-27 14:31:12 -04:00
relay.c kernel/relay.c: drop unneeded initialization 2020-10-16 11:11:22 -07:00
resource.c kernel/resource: make iomem_resource implicit in release_mem_region_adjustable() 2020-10-16 11:11:18 -07:00
rseq.c
scftorture.c scftorture: Add full-test stutter capability 2020-11-06 17:13:56 -08:00
scs.c scs: switch to vmapped shadow stacks 2020-12-01 10:30:28 +00:00
seccomp.c A set of updates for entry/exit handling: 2020-12-14 17:13:53 -08:00
signal.c A set of updates for entry/exit handling: 2020-12-14 17:13:53 -08:00
smp.c Merge branch 'linus' into sched/core, to resolve semantic conflict 2020-11-27 11:10:50 +01:00
smpboot.c
smpboot.h
softirq.c softirq: Add debug check to __raise_softirq_irqoff() 2020-09-16 15:18:56 +02:00
stackleak.c stackleak: let stack_erasing_sysctl take a kernel pointer buffer 2020-09-19 13:13:39 -07:00
stacktrace.c stacktrace: Remove reliable argument from arch_stack_walk() callback 2020-09-18 14:24:16 +01:00
static_call.c static_call: Fix return type of static_call_init 2020-10-02 21:18:25 +02:00
stop_machine.c Merge branch 'linus' into sched/core, to resolve semantic conflict 2020-11-27 11:10:50 +01:00
sys_ni.c mm/madvise: introduce process_madvise() syscall: an external memory hinting API 2020-10-18 09:27:10 -07:00
sys.c kernel: Implement selective syscall userspace redirection 2020-12-02 15:07:56 +01:00
sysctl-test.c
sysctl.c rcu: Panic after fixed number of stalls 2020-11-19 19:37:16 -08:00
task_work.c Merge branch 'core/urgent' into core/entry 2020-11-04 18:14:52 +01:00
taskstats.c treewide: rename nla_strlcpy to nla_strscpy. 2020-11-16 08:08:54 -08:00
test_kprobes.c
torture.c rcutorture: Make stutter_wait() caller restore priority 2020-11-06 17:13:54 -08:00
tracepoint.c tracepoints: Migrate to use SYSCALL_WORK flag 2020-11-16 21:53:15 +01:00
tsacct.c
ucount.c
uid16.c
uid16.h
umh.c usermodehelper: reset umask to default before executing user process 2020-10-06 10:31:52 -07:00
up.c
user_namespace.c fixes-v5.11 2020-12-14 16:40:27 -08:00
user-return-notifier.c
user.c user: Use generic ns_common::count 2020-08-19 14:14:12 +02:00
usermode_driver.c umd: Stop using split_argv 2020-07-07 11:58:59 -05:00
utsname_sysctl.c
utsname.c uts: Use generic ns_common::count 2020-08-19 14:13:20 +02:00
watch_queue.c watch_queue: Limit the number of watches a user can hold 2020-08-17 09:39:18 -07:00
watchdog_hld.c
watchdog.c kernel/watchdog: fix watchdog_allowed_mask not used warning 2020-11-14 11:26:03 -08:00
workqueue_internal.h
workqueue.c Merge branch 'akpm' (patches from Andrew) 2020-12-15 12:53:37 -08:00