Re: [PATCH] android: binder: fix binder mmap failures

[Andrey Ryabinin <a.ryabinin@samsung.com>]

On 02/27/2015 08:26 PM, John Stultz wrote:
> On Fri, Feb 27, 2015 at 8:30 AM, Andrey Ryabinin <a.ryabinin@samsung.com> wrote:
>> binder_update_page_range() initializes only addr and size
>> fields in 'struct vm_struct tmp_area;' and passes it to
>> map_vm_area().
>>
>> Before 71394fe50146 ("mm: vmalloc: add flag preventing guard hole allocation")
>> this was because map_vm_area() didn't use any other fields
>> in vm_struct except addr and size.
>>
>> Now get_vm_area_size() (used in map_vm_area()) reads vm_struct's
>> flags to determine whether vm area has guard hole or not.
>>
>> binder_update_page_range() don't initialize flags field, so
>> this causes following binder mmap failures:
>> -----------[ cut here ]------------
>> WARNING: CPU: 0 PID: 1971 at mm/vmalloc.c:130
>> vmap_page_range_noflush+0x119/0x144()
>> CPU: 0 PID: 1971 Comm: healthd Not tainted 4.0.0-rc1-00399-g7da3fdc-dirty #157
>> Hardware name: ARM-Versatile Express
>> [<c001246d>] (unwind_backtrace) from [<c000f7f9>] (show_stack+0x11/0x14)
>> [<c000f7f9>] (show_stack) from [<c049a221>] (dump_stack+0x59/0x7c)
>> [<c049a221>] (dump_stack) from [<c001cf21>] (warn_slowpath_common+0x55/0x84)
>> [<c001cf21>] (warn_slowpath_common) from [<c001cfe3>]
>> (warn_slowpath_null+0x17/0x1c)
>> [<c001cfe3>] (warn_slowpath_null) from [<c00c66c5>]
>> (vmap_page_range_noflush+0x119/0x144)
>> [<c00c66c5>] (vmap_page_range_noflush) from [<c00c716b>] (map_vm_area+0x27/0x48)
>> [<c00c716b>] (map_vm_area) from [<c038ddaf>]
>> (binder_update_page_range+0x12f/0x27c)
>> [<c038ddaf>] (binder_update_page_range) from [<c038e857>]
>> (binder_mmap+0xbf/0x1ac)
>> [<c038e857>] (binder_mmap) from [<c00c2dc7>] (mmap_region+0x2eb/0x4d4)
>> [<c00c2dc7>] (mmap_region) from [<c00c3197>] (do_mmap_pgoff+0x1e7/0x250)
>> [<c00c3197>] (do_mmap_pgoff) from [<c00b35b5>] (vm_mmap_pgoff+0x45/0x60)
>> [<c00b35b5>] (vm_mmap_pgoff) from [<c00c1f39>] (SyS_mmap_pgoff+0x5d/0x80)
>> [<c00c1f39>] (SyS_mmap_pgoff) from [<c000ce81>] (ret_fast_syscall+0x1/0x5c)
>> ---[ end trace 48c2c4b9a1349e54 ]---
>> binder: 1982: binder_alloc_buf failed to map page at f0e00000 in kernel
>> binder: binder_mmap: 1982 b6bde000-b6cdc000 alloc small buf failed -12
>>
>> Use map_kernel_range_noflush() instead of map_vm_area() as this is better
>> API for binder's purposes and it allows to get rid of 'vm_struct tmp_area' at all.
>>
>> Fixes: 71394fe50146 ("mm: vmalloc: add flag preventing guard hole allocation")
>> Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
>> Reported-by: Amit Pundir <amit.pundir@linaro.org>
>> ---
>>  drivers/android/binder.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
>> index 33b09b6..a984fbb 100644
>> --- a/drivers/android/binder.c
>> +++ b/drivers/android/binder.c
>> @@ -551,7 +551,6 @@ static int binder_update_page_range(struct binder_proc *proc, int allocate,
>>  {
>>         void *page_addr;
>>         unsigned long user_page_addr;
>> -       struct vm_struct tmp_area;
>>         struct page **page;
>>         struct mm_struct *mm;
>>
>> @@ -600,9 +599,10 @@ static int binder_update_page_range(struct binder_proc *proc, int allocate,
>>                                 proc->pid, page_addr);
>>                         goto err_alloc_page_failed;
>>                 }
>> -               tmp_area.addr = page_addr;
>> -               tmp_area.size = PAGE_SIZE + PAGE_SIZE /* guard page? */;
>> -               ret = map_vm_area(&tmp_area, PAGE_KERNEL, page);
>> +               ret = map_kernel_range_noflush((unsigned long)page_addr,
>> +                                       PAGE_SIZE, PAGE_KERNEL, page);
>> +               flush_cache_vmap((unsigned long)page_addr,
>> +                               (unsigned long)page_addr + PAGE_SIZE);
>>                 if (ret) {
>>                         pr_err("%d: binder_alloc_buf failed to map page at %p in kernel\n",
>>                                proc->pid, page_addr);
> 
> So with this patch I don't see the warnings, but I'm still seeing:
> [   11.154283] binder: 1956: binder_alloc_buf failed to map page at
> f0340000 in kernel
> [   11.154916] binder: binder_mmap: 1956 b6ce0000-b6d00000 alloc small
> buf failed -12
> 
> over and over.  So I don't think this patch is quite right.
> 

Thanks.

Seems that error check is wrong now.
map_vm_area() returns 0 on success, map_kernel_range_noflush() number of mapped pages.

> thanks
> -john
>