Re: [PATCH 1/1] dma-mapping: to avoid exception when cpu_addr is NULL

[Leizhen (ThunderTown)]

On 2016/3/8 6:59, Andrew Morton wrote:
> On Mon, 7 Mar 2016 18:43:47 +0800 "Leizhen (ThunderTown)" <thunder.leizhen@xxxxxxxxxx> wrote:
> 
>> Suppose:
>> CONFIG_SPARSEMEM is opened.
>> CONFIG_DMA_API_DEBUG or CONFIG_CMA is opened.
>>
>> Then virt_to_page or phys_to_page will be called. Finally, in __pfn_to_page, __sec = __pfn_to_section(__pfn) is NULL.
>> So access section->section_mem_map will trigger exception.
>>
>> ---------
>>
>> #define __pfn_to_page(pfn)				\
>> ({	unsigned long __pfn = (pfn);			\
>> 	struct mem_section *__sec = __pfn_to_section(__pfn);	\
>> 	__section_mem_map_addr(__sec) + __pfn;		\
>> })
>>
>> static inline struct page *__section_mem_map_addr(struct mem_section *section)
>> {
>> 	unsigned long map = section->section_mem_map;
>> 	map &= SECTION_MAP_MASK;
>> 	return (struct page *)map;
>> }
> 
> I'm having a bit of trouble understanding this.
> 
> Perhaps you could explain the bug more carefully (inclusion of an oops
> output would help) then we'll be in a better position to understand the
> proposed fix(es).
> 

Unable to handle kernel paging request at virtual address ffffffc020d3b2b8
pgd = ffffffc083a61000
[ffffffc020d3b2b8] *pgd=0000000000000000, *pud=0000000000000000
CPU: 4 PID: 1489 Comm: malloc_dma_1 Tainted: G           O
Hardware name:
task: ffffffc00d7d26c0 ti: ffffffc0837fc000 task.ti: ffffffc0837fc000
PC is at __dma_free_coherent.isra.10+0x74/0xc8
LR is at __dma_free+0x9c/0xb0
pc : [<ffffffc000214d10>] lr : [<ffffffc000214e00>] pstate: 80000145
sp : ffffffc0837ff700
x29: ffffffc0837ff700 x28: 0000000000000000
x27: 0000000000000000 x26: ffffffffffffffff
x25: ffffffc000d1b1d0 x24: ffffffffffffffff
x23: 0000000000a00000 x22: ffffffbfff5fffff
x21: 0000000000100000 x20: ffffffc2e21f7010
x19: ffffffffffffffff x18: 0000000000000000
x17: 0000007f9360a2b0 x16: ffffffc000541040
x15: ffffffffffffffff x14: ffffffffffffffff
x13: ffffffffffffffff x12: 0000000000000001
x11: 0000000000000068 x10: 0000000000000040
x9 : ffffffc000214e00 x8 : ffffffc2e54586b0
x7 : 0000000000000000 x6 : 0000000000000004
x5 : ffffffc000214d64 x4 : 0000000000000000
x3 : 0000000003ffffff x2 : 00000003ffffffff
x1 : 000fffffffffffff x0 : ffffffc000d3b2c0

Process malloc_dma_1 (pid: 1489, stack limit = 0xffffffc0837fc020)
Stack: (0xffffffc0837ff700 to 0xffffffc083800000)
f700: ffffffc0837ff730 ffffffc000214e00 0000000000100000 0000000000000000
f720: ffffffc2e21f7010 ffffffc0837ff7d0 ffffffc0837ff770 ffffffbffc1d6134
f740: ffffffc2e21f7010 00000000000001a0 0000000000000064 ffffffc0837ff7d0
f760: ffffffc000c9fa20 ffffffc0837ffaf0 ffffffc0837ffe10 ffffffc000239b0c
f780: ffffffc00d54a280 ffffffc000d1ef58 ffffffc000957163 ffffffc2e21f7000
f7a0: ffffffbffc1d6030 0000000000000000 0000000000000000 0000000000000000
f7c0: 0000000000000000 0000000000000000 ffffffc013000000 ffffffc013c00000
f7e0: ffffffc013f00000 ffffffc014200000 ffffffc014600000 ffffffc014a00000
f800: ffffffc014e00000 ffffffc015200000 ffffffc015600000 ffffffc015a00000
f820: ffffffc015e00000 ffffffc016200000 ffffffc016600000 ffffffc016a00000
f840: ffffffc016e00000 ffffffc017200000 ffffffc017600000 ffffffc017a00000
f860: ffffffc017e00000 ffffffc018200000 ffffffc018600000 ffffffc018a00000
f880: ffffffc018e00000 ffffffc019200000 ffffffc019600000 ffffffc019a00000
f8a0: ffffffc019e00000 ffffffc01a200000 ffffffc01a600000 ffffffc01aa00000
f8c0: ffffffc01ae00000 ffffffc01b200000 ffffffc01b600000 ffffffc01ba00000
f8e0: ffffffc01be00000 ffffffc01c200000 ffffffc01c600000 ffffffc01ca00000
f900: ffffffc01ce00000 ffffffc01d200000 ffffffc01d600000 ffffffc01da00000
f920: ffffffc01de00000 ffffffc01e200000 ffffffc01e400000 ffffffc01e600000
f940: ffffffc01e900000 ffffffc01ea00000 ffffffc01eb00000 ffffffc01ec00000
f960: ffffffc01ee00000 ffffffc01f200000 0000000000000000 0000000000000000
f980: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
f9a0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
f9c0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
f9e0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
fa00: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
fa20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
fa40: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
fa60: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
fa80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
faa0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
fac0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
fae0: 0000000000000000 0000000000000000 0000000013a00000 0000000014600000
fb00: 0000000014900000 0000000014c00000 0000000015000000 0000000015400000
fb20: 0000000015800000 0000000015c00000 0000000016000000 0000000016400000
fb40: 0000000016800000 0000000016c00000 0000000017000000 0000000017400000
fb60: 0000000017800000 0000000017c00000 0000000018000000 0000000018400000
fb80: 0000000018800000 0000000018c00000 0000000019000000 0000000019400000
fba0: 0000000019800000 0000000019c00000 000000001a000000 000000001a400000
fbc0: 000000001a800000 000000001ac00000 000000001b000000 000000001b400000
fbe0: 000000001b800000 000000001bc00000 000000001c000000 000000001c400000
fc00: 000000001c800000 000000001cc00000 000000001d000000 000000001d400000
fc20: 000000001d800000 000000001dc00000 000000001e000000 000000001e400000
fc40: 000000001e800000 000000001ec00000 000000001ee00000 000000001f000000
fc60: 000000001f300000 000000001f400000 000000001f500000 000000001f600000
fc80: 000000001f800000 000000001fc00000 ffffffffffffffff ffffffffffffffff
fca0: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
fcc0: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
fce0: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
fd00: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
fd20: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
fd40: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
fd60: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
fd80: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
fda0: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
fdc0: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
fde0: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
fe00: ffffffffffffffff ffffffffffffffff 0000000000000000 ffffffc0002045b0
fe20: ffffffc000239a20 ffffffc00d54a280 0000000000000000 0000000000000000
fe40: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
fe60: ffffffc0837ffe80 ffffffc2e21f7000 00000000e54c1280 0000000000000000
fe80: 0000000000000000 0040000100244964 ffffffc0837ffe90 ffffffc0837ffe90
fea0: 0000000000000000 0000000000000000 0000000000000000 00400001002045a4
fec0: ffffffc0837ffec0 ffffffc0837ffec0 0000000000000000 0000000000000000
fee0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
ff00: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
ff20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
ff40: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
ff60: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
ff80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
ffa0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
ffc0: 0000000000000000 0000000000000000 0000000000000000 0000000000000005
ffe0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
Call trace:
[<ffffffc000214d10>] __dma_free_coherent.isra.10+0x74/0xc8
[<ffffffc000214e00>] __dma_free+0x9c/0xb0
[<ffffffbffc1d6134>] malloc_dma+0x104/0x158 [dma_alloc_coherent_mtmalloc]
[<ffffffc000239b0c>] kthread+0xec/0xfc
Code: 62fc5ed3 205900f0 00000b91 63fc66d3 (007863f8)
---[ end trace 8b2106a7528c8712 ]---



> Thanks.
> 
> .
>