linux-kernel - Re: [PATCH v3 3/3] powerpc/32: Add KASAN support

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Date:   Mon, 21 Jan 2019 08:17:03 +0100
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        kasan-dev@...glegroups.com, linux-mm@...ck.org
Subject: Re: [PATCH v3 3/3] powerpc/32: Add KASAN support



Le 15/01/2019 à 18:23, Andrey Ryabinin a écrit :
> 
> 
> On 1/12/19 2:16 PM, Christophe Leroy wrote:
> 
>> +KASAN_SANITIZE_early_32.o := n
>> +KASAN_SANITIZE_cputable.o := n
>> +KASAN_SANITIZE_prom_init.o := n
>> +
> 
> Usually it's also good idea to disable branch profiling - define DISABLE_BRANCH_PROFILING
> either in top of these files or via Makefile. Branch profiling redefines if() statement and calls
> instrumented ftrace_likely_update in every if().
> 
> 
> 
>> diff --git a/arch/powerpc/mm/kasan_init.c b/arch/powerpc/mm/kasan_init.c
>> new file mode 100644
>> index 000000000000..3edc9c2d2f3e
> 
>> +void __init kasan_init(void)
>> +{
>> +	struct memblock_region *reg;
>> +
>> +	for_each_memblock(memory, reg)
>> +		kasan_init_region(reg);
>> +
>> +	pr_info("KASAN init done\n");
> 
> Without "init_task.kasan_depth = 0;" kasan will not repot bugs.
> 
> There is test_kasan module. Make sure that it produce reports.
> 

Thanks for the review.

Now I get the following very early in boot, what does that mean ?

[    0.000000] KASAN init done
[    0.000000] 
==================================================================
[    0.000000] BUG: KASAN: unknown-crash in memblock_alloc_try_nid+0xd8/0xf0
[    0.000000] Write of size 68 at addr c7ff5a90 by task swapper/0
[    0.000000]
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 
5.0.0-rc2-s3k-dev-00559-g88aa407c4bce #772
[    0.000000] Call Trace:
[    0.000000] [c094ded0] [c016c7e4] 
print_address_description+0x1a0/0x2b8 (unreliable)
[    0.000000] [c094df00] [c016caa0] kasan_report+0xe4/0x168
[    0.000000] [c094df40] [c016b464] memset+0x2c/0x4c
[    0.000000] [c094df60] [c08731f0] memblock_alloc_try_nid+0xd8/0xf0
[    0.000000] [c094df90] [c0861f20] mmu_context_init+0x58/0xa0
[    0.000000] [c094dfb0] [c085ca70] start_kernel+0x54/0x400
[    0.000000] [c094dff0] [c0002258] start_here+0x44/0x9c
[    0.000000]
[    0.000000]
[    0.000000] Memory state around the buggy address:
[    0.000000]  c7ff5980: e2 a1 87 81 bd d4 a5 b5 f8 8d 89 e7 72 bc 20 24
[    0.000000]  c7ff5a00: e7 b9 c1 c7 17 e9 b4 bd a4 d0 e7 a0 11 15 a5 b5
[    0.000000] >c7ff5a80: b5 e1 83 a5 2d 65 31 3f f3 e5 a7 ef 34 b5 69 b5
[    0.000000]                  ^
[    0.000000]  c7ff5b00: 21 a5 c1 c1 b4 bf 2d e5 e5 c3 f5 91 e3 b8 a1 34
[    0.000000]  c7ff5b80: ad ef 23 87 3d a6 ad b5 c3 c3 80 b7 ac b1 1f 37
[    0.000000] 
==================================================================
[    0.000000] Disabling lock debugging due to kernel taint
[    0.000000] MMU: Allocated 76 bytes of context maps for 16 contexts
[    0.000000] Built 1 zonelists, mobility grouping on.  Total pages: 8176
[    0.000000] Kernel command line: console=ttyCPM0,115200N8 
ip=192.168.2.7:192.168.2.2::255.0.0.0:vgoip:eth0:off kgdboc=ttyCPM0
[    0.000000] Dentry cache hash table entries: 16384 (order: 2, 65536 
bytes)
[    0.000000] Inode-cache hash table entries: 8192 (order: 1, 32768 bytes)
[    0.000000] Memory: 99904K/131072K available (7376K kernel code, 528K 
rwdata, 1168K rodata, 576K init, 4623K bss, 31168K reserved, 0K 
cma-reserved)
[    0.000000] Kernel virtual memory layout:
[    0.000000]   * 0xffefc000..0xffffc000  : fixmap
[    0.000000]   * 0xf7c00000..0xffc00000  : kasan shadow mem
[    0.000000]   * 0xf7a00000..0xf7c00000  : consistent mem
[    0.000000]   * 0xf7a00000..0xf7a00000  : early ioremap
[    0.000000]   * 0xc9000000..0xf7a00000  : vmalloc & ioremap


Christophe