[WIP] Fix infinite recursion during KMSAN initialization

KSAN calls into rcu code which then triggers a write that reenters into KSAN
getting the system stuck doing infinite recursion.

#0  kmsan_get_context () at mm/kmsan/kmsan.h:106
#1  __msan_get_context_state () at mm/kmsan/instrumentation.c:331
#2  0xffffffff81495671 in get_current () at ./arch/x86/include/asm/current.h:42
#3  rcu_preempt_read_enter () at kernel/rcu/tree_plugin.h:379
#4  __rcu_read_lock () at kernel/rcu/tree_plugin.h:402
#5  0xffffffff81b2054b in rcu_read_lock () at ./include/linux/rcupdate.h:748
torvalds#6  pfn_valid (pfn=<optimized out>) at ./include/linux/mmzone.h:2016
torvalds#7  kmsan_virt_addr_valid (addr=addr@entry=0xffffffff8620d974 <init_task+1012>) at ./arch/x86/include/asm/kmsan.h:82
torvalds#8  virt_to_page_or_null (vaddr=vaddr@entry=0xffffffff8620d974 <init_task+1012>) at mm/kmsan/shadow.c:75
torvalds#9  0xffffffff81b2023c in kmsan_get_metadata (address=0xffffffff8620d974 <init_task+1012>, is_origin=false) at mm/kmsan/shadow.c:143
torvalds#10 kmsan_get_shadow_origin_ptr (address=0xffffffff8620d974 <init_task+1012>, size=4, store=false) at mm/kmsan/shadow.c:97
torvalds#11 0xffffffff81b1dbd2 in get_shadow_origin_ptr (addr=0xffffffff8620d974 <init_task+1012>, size=4, store=false) at mm/kmsan/instrumentation.c:36
torvalds#12 __msan_metadata_ptr_for_load_4 (addr=0xffffffff8620d974 <init_task+1012>) at mm/kmsan/instrumentation.c:91
torvalds#13 0xffffffff8149568f in rcu_preempt_read_enter () at kernel/rcu/tree_plugin.h:379
torvalds#14 __rcu_read_lock () at kernel/rcu/tree_plugin.h:402
torvalds#15 0xffffffff81b2054b in rcu_read_lock () at ./include/linux/rcupdate.h:748
torvalds#16 pfn_valid (pfn=<optimized out>) at ./include/linux/mmzone.h:2016
torvalds#17 kmsan_virt_addr_valid (addr=addr@entry=0xffffffff8620d974 <init_task+1012>) at ./arch/x86/include/asm/kmsan.h:82
torvalds#18 virt_to_page_or_null (vaddr=vaddr@entry=0xffffffff8620d974 <init_task+1012>) at mm/kmsan/shadow.c:75
torvalds#19 0xffffffff81b2023c in kmsan_get_metadata (address=0xffffffff8620d974 <init_task+1012>, is_origin=false) at mm/kmsan/shadow.c:143
torvalds#20 kmsan_get_shadow_origin_ptr (address=0xffffffff8620d974 <init_task+1012>, size=4, store=false) at mm/kmsan/shadow.c:97
torvalds#21 0xffffffff81b1dbd2 in get_shadow_origin_ptr (addr=0xffffffff8620d974 <init_task+1012>, size=4, store=false) at mm/kmsan/instrumentation.c:36
torvalds#22 __msan_metadata_ptr_for_load_4 (addr=0xffffffff8620d974 <init_task+1012>) at mm/kmsan/instrumentation.c:91
torvalds#23 0xffffffff8149568f in rcu_preempt_read_enter () at kernel/rcu/tree_plugin.h:379
torvalds#24 __rcu_read_lock () at kernel/rcu/tree_plugin.h:402
torvalds#25 0xffffffff81b2054b in rcu_read_lock () at ./include/linux/rcupdate.h:748
torvalds#26 pfn_valid (pfn=<optimized out>) at ./include/linux/mmzone.h:2016
torvalds#27 kmsan_virt_addr_valid (addr=addr@entry=0xffffffff8620d974 <init_task+1012>) at ./arch/x86/include/asm/kmsan.h:82
torvalds#28 virt_to_page_or_null (vaddr=vaddr@entry=0xffffffff8620d974 <init_task+1012>) at mm/kmsan/shadow.c:75
torvalds#29 0xffffffff81b2023c in kmsan_get_metadata (address=0xffffffff8620d974 <init_task+1012>, is_origin=false) at mm/kmsan/shadow.c:143
torvalds#30 kmsan_get_shadow_origin_ptr (address=0xffffffff8620d974 <init_task+1012>, size=4, store=false) at mm/kmsan/shadow.c:97
torvalds#31 0xffffffff81b1dbd2 in get_shadow_origin_ptr (addr=0xffffffff8620d974 <init_task+1012>, size=4, store=false) at mm/kmsan/instrumentation.c:36
torvalds#32 __msan_metadata_ptr_for_load_4 (addr=0xffffffff8620d974 <init_task+1012>) at mm/kmsan/instrumentation.c:91
torvalds#33 0xffffffff8149568f in rcu_preempt_read_enter () at kernel/rcu/tree_plugin.h:379
torvalds#34 __rcu_read_lock () at kernel/rcu/tree_plugin.h:402
torvalds#35 0xffffffff81b2054b in rcu_read_lock () at ./include/linux/rcupdate.h:748
torvalds#36 pfn_valid (pfn=<optimized out>) at ./include/linux/mmzone.h:2016
torvalds#37 kmsan_virt_addr_valid (addr=addr@entry=0xffffffff8620d974 <init_task+1012>) at ./arch/x86/include/asm/kmsan.h:82
torvalds#38 virt_to_page_or_null (vaddr=vaddr@entry=0xffffffff8620d974 <init_task+1012>) at mm/kmsan/shadow.c:75
torvalds#39 0xffffffff81b2023c in kmsan_get_metadata (address=0xffffffff8620d974 <init_task+1012>, is_origin=false) at mm/kmsan/shadow.c:143
torvalds#40 kmsan_get_shadow_origin_ptr (address=0xffffffff8620d974 <init_task+1012>, size=4, store=false) at mm/kmsan/shadow.c:97
torvalds#41 0xffffffff81b1dbd2 in get_shadow_origin_ptr (addr=0xffffffff8620d974 <init_task+1012>, size=4, store=false) at mm/kmsan/instrumentation.c:36
torvalds#42 __msan_metadata_ptr_for_load_4 (addr=0xffffffff8620d974 <init_task+1012>) at mm/kmsan/instrumentation.c:91
torvalds#43 0xffffffff8149568f in rcu_preempt_read_enter () at kernel/rcu/tree_plugin.h:379
torvalds#44 __rcu_read_lock () at kernel/rcu/tree_plugin.h:402
torvalds#45 0xffffffff81b2054b in rcu_read_lock () at ./include/linux/rcupdate.h:748
torvalds#46 pfn_valid (pfn=<optimized out>) at ./include/linux/mmzone.h:2016
torvalds#47 kmsan_virt_addr_valid (addr=addr@entry=0xffffffff8620d974 <init_task+1012>) at ./arch/x86/include/asm/kmsan.h:82
torvalds#48 virt_to_page_or_null (vaddr=vaddr@entry=0xffffffff8620d974 <init_task+1012>) at mm/kmsan/shadow.c:75
torvalds#49 0xffffffff81b2023c in kmsan_get_metadata (address=0xffffffff8620d974 <init_task+1012>, is_origin=false) at mm/kmsan/shadow.c:143
torvalds#50 kmsan_get_shadow_origin_ptr (address=0xffffffff8620d974 <init_task+1012>, size=4, store=false) at mm/kmsan/shadow.c:97
torvalds#51 0xffffffff81b1dbd2 in get_shadow_origin_ptr (addr=0xffffffff8620d974 <init_task+1012>, size=4, store=false) at mm/kmsan/instrumentation.c:36
#52 __msan_metadata_ptr_for_load_4 (addr=0xffffffff8620d974 <init_task+1012>) at mm/kmsan/instrumentation.c:91
#53 0xffffffff8149568f in rcu_preempt_read_enter () at kernel/rcu/tree_plugin.h:379
torvalds#54 __rcu_read_lock () at kernel/rcu/tree_plugin.h:402
torvalds#55 0xffffffff81b2054b in rcu_read_lock () at ./include/linux/rcupdate.h:748
torvalds#56 pfn_valid (pfn=<optimized out>) at ./include/linux/mmzone.h:2016
torvalds#57 kmsan_virt_addr_valid (addr=addr@entry=0xffffffff8620d974 <init_task+1012>) at ./arch/x86/include/asm/kmsan.h:82
#58 virt_to_page_or_null (vaddr=vaddr@entry=0xffffffff8620d974 <init_task+1012>) at mm/kmsan/shadow.c:75
torvalds#59 0xffffffff81b2023c in kmsan_get_metadata (address=0xffffffff8620d974 <init_task+1012>, is_origin=false) at mm/kmsan/shadow.c:143
torvalds#60 kmsan_get_shadow_origin_ptr (address=0xffffffff8620d974 <init_task+1012>, size=4, store=false) at mm/kmsan/shadow.c:97
torvalds#61 0xffffffff81b1dbd2 in get_shadow_origin_ptr (addr=0xffffffff8620d974 <init_task+1012>, size=4, store=false) at mm/kmsan/instrumentation.c:36
torvalds#62 __msan_metadata_ptr_for_load_4 (addr=0xffffffff8620d974 <init_task+1012>) at mm/kmsan/instrumentation.c:91
torvalds#63 0xffffffff8149568f in rcu_preempt_read_enter () at kernel/rcu/tree_plugin.h:379
torvalds#64 __rcu_read_lock () at kernel/rcu/tree_plugin.h:402
torvalds#65 0xffffffff81b2054b in rcu_read_lock () at ./include/linux/rcupdate.h:748
torvalds#66 pfn_valid (pfn=<optimized out>) at ./include/linux/mmzone.h:2016
torvalds#67 kmsan_virt_addr_valid (addr=addr@entry=0xffffffff8620d974 <init_task+1012>) at ./arch/x86/include/asm/kmsan.h:82
torvalds#68 virt_to_page_or_null (vaddr=vaddr@entry=0xffffffff8620d974 <init_task+1012>) at mm/kmsan/shadow.c:75
torvalds#69 0xffffffff81b2023c in kmsan_get_metadata (address=0xffffffff8620d974 <init_task+1012>, is_origin=false) at mm/kmsan/shadow.c:143
#70 kmsan_get_shadow_origin_ptr (address=0xffffffff8620d974 <init_task+1012>, size=4, store=false) at mm/kmsan/shadow.c:97
torvalds#71 0xffffffff81b1dbd2 in get_shadow_origin_ptr (addr=0xffffffff8620d974 <init_task+1012>, size=4, store=false) at mm/kmsan/instrumentation.c:36
torvalds#72 __msan_metadata_ptr_for_load_4 (addr=0xffffffff8620d974 <init_task+1012>) at mm/kmsan/instrumentation.c:91
torvalds#73 0xffffffff8149568f in rcu_preempt_read_enter () at kernel/rcu/tree_plugin.h:379
torvalds#74 __rcu_read_lock () at kernel/rcu/tree_plugin.h:402
torvalds#75 0xffffffff81b2054b in rcu_read_lock () at ./include/linux/rcupdate.h:748
torvalds#76 pfn_valid (pfn=<optimized out>) at ./include/linux/mmzone.h:2016
torvalds#77 kmsan_virt_addr_valid (addr=addr@entry=0xffffffff86203c90) at ./arch/x86/include/asm/kmsan.h:82
torvalds#78 virt_to_page_or_null (vaddr=vaddr@entry=0xffffffff86203c90) at mm/kmsan/shadow.c:75
torvalds#79 0xffffffff81b2023c in kmsan_get_metadata (address=0xffffffff86203c90, is_origin=false) at mm/kmsan/shadow.c:143
torvalds#80 kmsan_get_shadow_origin_ptr (address=0xffffffff86203c90, size=8, store=false) at mm/kmsan/shadow.c:97
torvalds#81 0xffffffff81b1dc72 in get_shadow_origin_ptr (addr=0xffffffff8620d974 <init_task+1012>, size=8, store=false) at mm/kmsan/instrumentation.c:36
torvalds#82 __msan_metadata_ptr_for_load_8 (addr=0xffffffff8620d974 <init_task+1012>) at mm/kmsan/instrumentation.c:92
torvalds#83 0xffffffff814fdb9e in filter_irq_stacks (entries=<optimized out>, nr_entries=4) at kernel/stacktrace.c:397
torvalds#84 0xffffffff829520e8 in stack_depot_save_flags (entries=0xffffffff8620d974 <init_task+1012>, nr_entries=4, alloc_flags=0, depot_flags=0) at lib/stackdepot.c:500
torvalds#85 0xffffffff81b1e560 in __msan_poison_alloca (address=0xffffffff86203da0, size=24, descr=<optimized out>) at mm/kmsan/instrumentation.c:285
torvalds#86 0xffffffff8562821c in _printk (fmt=0xffffffff85f191a5 "\0016Attempting lock1") at kernel/printk/printk.c:2324
torvalds#87 0xffffffff81942aa2 in kmem_cache_create_usercopy (name=0xffffffff85f18903 "mm_struct", size=1296, align=0, flags=270336, useroffset=<optimized out>, usersize=<optimized out>, ctor=0x0 <fixed_percpu_data>) at mm/slab_common.c:296
torvalds#88 0xffffffff86f337a0 in mm_cache_init () at kernel/fork.c:3262
torvalds#89 0xffffffff86eacb8e in start_kernel () at init/main.c:932
torvalds#90 0xffffffff86ecdf94 in x86_64_start_reservations (real_mode_data=0x140e0 <exception_stacks+28896> <error: Cannot access memory at address 0x140e0>) at arch/x86/kernel/head64.c:555
torvalds#91 0xffffffff86ecde9b in x86_64_start_kernel (real_mode_data=0x140e0 <exception_stacks+28896> <error: Cannot access memory at address 0x140e0>) at arch/x86/kernel/head64.c:536
torvalds#92 0xffffffff810001d3 in secondary_startup_64 () at /pool/workspace/linux/arch/x86/kernel/head_64.S:461
torvalds#93 0x0000000000000000 in ??

kernel/rcu/Makefile

@@ -7,6 +7,9 @@ ifeq ($(CONFIG_KCSAN),y)
 KBUILD_CFLAGS += -g -fno-omit-frame-pointer
 endif
 
+# Avoid recursion KMSAN -> tree -> KMSAN -> tree.
+KMSAN_SANITIZE_tree.o := n
+
 obj-y += update.o sync.o
 obj-$(CONFIG_TREE_SRCU) += srcutree.o
 obj-$(CONFIG_TINY_SRCU) += srcutiny.o