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forked fromtorvalds/linux

Commitb0845ce

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mrutland-armtorvalds
authored andcommitted
kasan: report only the first error by default
Disable kasan after the first report. There are several reasons forthis: - Single bug quite often has multiple invalid memory accesses causing storm in the dmesg. - Write OOB access might corrupt metadata so the next report will print bogus alloc/free stacktraces. - Reports after the first easily could be not bugs by itself but just side effects of the first one.Given that multiple reports usually only do harm, it makes sense todisable kasan after the first one. If user wants to see all thereports, the boot-time parameter kasan_multi_shot must be used.[aryabinin@virtuozzo.com: wrote changelog and doc, added missing include]Link:http://lkml.kernel.org/r/20170323154416.30257-1-aryabinin@virtuozzo.comSigned-off-by: Mark Rutland <mark.rutland@arm.com>Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>Cc: Andrey Konovalov <andreyknvl@google.com>Cc: Alexander Potapenko <glider@google.com>Cc: Dmitry Vyukov <dvyukov@google.com>Signed-off-by: Andrew Morton <akpm@linux-foundation.org>Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent4742a35 commitb0845ce

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5 files changed

+55
-5
lines changed

5 files changed

+55
-5
lines changed

‎Documentation/admin-guide/kernel-parameters.txt‎

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@@ -1725,6 +1725,12 @@
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kernel and module base offset ASLR (Address Space
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Layout Randomization).
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kasan_multi_shot
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[KNL] Enforce KASAN (Kernel Address Sanitizer) to print
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report on every invalid memory access. Without this
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parameter KASAN will print report only for the first
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invalid access.
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keepinitrd[HW,ARM]
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kernelcore=[KNL,X86,IA-64,PPC]

‎include/linux/kasan.h‎

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@@ -76,6 +76,9 @@ size_t ksize(const void *);
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staticinlinevoidkasan_unpoison_slab(constvoid*ptr) {ksize(ptr); }
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size_tkasan_metadata_size(structkmem_cache*cache);
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79+
boolkasan_save_enable_multi_shot(void);
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voidkasan_restore_multi_shot(boolenabled);
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#else/* CONFIG_KASAN */
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staticinlinevoidkasan_unpoison_shadow(constvoid*address,size_tsize) {}

‎lib/test_kasan.c‎

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@@ -20,6 +20,7 @@
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#include<linux/string.h>
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#include<linux/uaccess.h>
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#include<linux/module.h>
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#include<linux/kasan.h>
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/*
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* Note: test functions are marked noinline so that their names appear in
@@ -474,6 +475,12 @@ static noinline void __init use_after_scope_test(void)
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staticint__initkmalloc_tests_init(void)
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{
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/*
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* Temporarily enable multi-shot mode. Otherwise, we'd only get a
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* report for the first case.
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*/
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boolmultishot=kasan_save_enable_multi_shot();
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kmalloc_oob_right();
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kmalloc_oob_left();
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kmalloc_node_oob_right();
@@ -499,6 +506,9 @@ static int __init kmalloc_tests_init(void)
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ksize_unpoisons_memory();
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copy_user_test();
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use_after_scope_test();
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kasan_restore_multi_shot(multishot);
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return-EAGAIN;
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}
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‎mm/kasan/kasan.h‎

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@@ -96,11 +96,6 @@ static inline const void *kasan_shadow_to_mem(const void *shadow_addr)
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<<KASAN_SHADOW_SCALE_SHIFT);
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}
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staticinlineboolkasan_report_enabled(void)
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{
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return !current->kasan_depth;
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}
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voidkasan_report(unsigned longaddr,size_tsize,
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boolis_write,unsigned longip);
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voidkasan_report_double_free(structkmem_cache*cache,void*object,

‎mm/kasan/report.c‎

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@@ -13,7 +13,9 @@
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*
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*/
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#include<linux/bitops.h>
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#include<linux/ftrace.h>
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#include<linux/init.h>
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#include<linux/kernel.h>
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#include<linux/mm.h>
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#include<linux/printk.h>
@@ -293,6 +295,40 @@ static void kasan_report_error(struct kasan_access_info *info)
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kasan_end_report(&flags);
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}
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staticunsigned longkasan_flags;
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#defineKASAN_BIT_REPORTED0
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#defineKASAN_BIT_MULTI_SHOT1
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boolkasan_save_enable_multi_shot(void)
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{
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returntest_and_set_bit(KASAN_BIT_MULTI_SHOT,&kasan_flags);
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}
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EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
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voidkasan_restore_multi_shot(boolenabled)
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{
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if (!enabled)
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clear_bit(KASAN_BIT_MULTI_SHOT,&kasan_flags);
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}
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EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
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staticint__initkasan_set_multi_shot(char*str)
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{
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set_bit(KASAN_BIT_MULTI_SHOT,&kasan_flags);
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return1;
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}
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__setup("kasan_multi_shot",kasan_set_multi_shot);
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staticinlineboolkasan_report_enabled(void)
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{
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if (current->kasan_depth)
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return false;
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if (test_bit(KASAN_BIT_MULTI_SHOT,&kasan_flags))
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return true;
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return !test_and_set_bit(KASAN_BIT_REPORTED,&kasan_flags);
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}
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voidkasan_report(unsigned longaddr,size_tsize,
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boolis_write,unsigned longip)
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{

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