Re: [Intel-gfx] [v2] drm/i915/gem: missing boundary check in vm_access leads to OOB read/write

[Matthew Auld <matthew.auld@intel.com>]

On 09/03/2022 11:19, Katragadda, MastanX wrote:
> Hi,
> 
> can we have ack? or we need to do anything further to get r-o-b.

There was just the potential strangeness around len <= 0, and exactly 
how we are meant to handle that, but if you are confident that is 
already covered in a sane way, then feel free to add,
Reviewed-by: Matthew Auld <matthew.auld@intel.com>

> 
> Thanks,
> Mastan
> 
> -----Original Message-----
> From: Katragadda, MastanX
> Sent: 09 March 2022 07:16
> To: Auld, Matthew <matthew.auld@intel.com>; Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>; intel-gfx@lists.freedesktop.org
> Cc: Surendrakumar Upadhyay, TejaskumarX <tejaskumarx.surendrakumar.upadhyay@intel.com>
> Subject: RE: [Intel-gfx] [v2] drm/i915/gem: missing boundary check in vm_access leads to OOB read/write
> 
> On 03/03/2022 09:00, Tvrtko Ursulin wrote:
>>
>> + Matt
>>
>> On 03/03/2022 06:04, Mastan Katragadda wrote:
>>> Intel ID: PSIRT-PTK0002429
>>>
>>> A missing bounds check in vm_access()can lead to an out-of-bounds
>>> read or write in the adjacent memory area.The len attribute is not
>>> validated before the memcpy at  [1]or [2] occurs.
>>
>> s/[1]or [2]/later in the function/ ?
>>
>>>
>>> [  183.637831] BUG: unable to handle page fault for address:
>>> ffffc90000c86000
>>> [  183.637934] #PF: supervisor read access in kernel mode [
>>> 183.637997] #PF: error_code(0x0000) - not-present page [  183.638059]
>>> PGD 100000067 P4D 100000067 PUD 100258067 PMD 106341067 PTE 0 [
>>> 183.638144] Oops: 0000 [#2] PREEMPT SMP NOPTI
>>> [  183.638201] CPU: 3 PID: 1790 Comm: poc Tainted: G      D
>>> 5.17.0-rc6-ci-drm-11296+ #1
>>> [  183.638298] Hardware name: Intel Corporation CoffeeLake Client
>>> Platform/CoffeeLake H DDR4 RVP, BIOS CNLSFWR1.R00.X208.B00.1905301319
>>> 05/30/2019
>>> [  183.638430] RIP: 0010:memcpy_erms+0x6/0x10 [  183.640213] RSP:
>>> 0018:ffffc90001763d48 EFLAGS: 00010246 [  183.641117] RAX:
>>> ffff888109c14000 RBX: ffff888111bece40 RCX:
>>> 0000000000000ffc
>>> [  183.642029] RDX: 0000000000001000 RSI: ffffc90000c86000 RDI:
>>> ffff888109c14004
>>> [  183.642946] RBP: 0000000000000ffc R08: 800000000000016b R09:
>>> 0000000000000000
>>> [  183.643848] R10: ffffc90000c85000 R11: 0000000000000048 R12:
>>> 0000000000001000
>>> [  183.644742] R13: ffff888111bed190 R14: ffff888109c14000 R15:
>>> 0000000000001000
>>> [  183.645653] FS:  00007fe5ef807540(0000) GS:ffff88845b380000(0000)
>>> knlGS:0000000000000000
>>> [  183.646570] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [
>>> 183.647481] CR2: ffffc90000c86000 CR3: 000000010ff02006 CR4:
>>> 00000000003706e0
>>> [  183.648384] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
>>> 0000000000000000
>>> [  183.649271] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
>>> 0000000000000400
>>> [  183.650142] Call Trace:
>>> [  183.650988]  <TASK>
>>> [  183.651793]  vm_access+0x1f0/0x2a0 [i915] [  183.652726]
>>> __access_remote_vm+0x224/0x380 [  183.653561]
>>> mem_rw.isra.0+0xf9/0x190 [  183.654402]  vfs_read+0x9d/0x1b0 [
>>> 183.655238]  ksys_read+0x63/0xe0 [  183.656065]
>>> do_syscall_64+0x38/0xc0 [  183.656882]
>>> entry_SYSCALL_64_after_hwframe+0x44/0xae
>>> [  183.657663] RIP: 0033:0x7fe5ef725142 [  183.659351] RSP:
>>> 002b:00007ffe1e81c7e8 EFLAGS: 00000246 ORIG_RAX:
>>> 0000000000000000
>>> [  183.660227] RAX: ffffffffffffffda RBX: 0000557055dfb780 RCX:
>>> 00007fe5ef725142
>>> [  183.661104] RDX: 0000000000001000 RSI: 00007ffe1e81d880 RDI:
>>> 0000000000000005
>>> [  183.661972] RBP: 00007ffe1e81e890 R08: 0000000000000030 R09:
>>> 0000000000000046
>>> [  183.662832] R10: 0000557055dfc2e0 R11: 0000000000000246 R12:
>>> 0000557055dfb1c0
>>> [  183.663691] R13: 00007ffe1e81e980 R14: 0000000000000000 R15:
>>> 0000000000000000
>>> [  183.664566]  </TASK>
>>>
>>> Changes since v1:
>>>        - Updated if condition with range_overflows_t [Chris Wilson]
>>>
>>> Signed-off-by: Mastan Katragadda <mastanx.katragadda@intel.com>
>>> Suggested-by: Adam Zabrocki <adamza@microsoft.com>
>>> Reported-by: Jackson Cody <cody.jackson@intel.com>
>>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
>>> Cc: Bloomfield Jon <jon.bloomfield@intel.com>
>>> Cc: Dutt Sudeep <sudeep.dutt@intel.com>
>>
>> Fixes: 9f909e215fea ("drm/i915: Implement vm_ops->access for gdb
>> access into mmaps")
>> Cc: <stable@vger.kernel.org> # v5.8+
>>
>> Right?
>>
>> There was a selftest added with the referenced patch and it sounds
>> like it would be a good idea to extend it to cover this scenario.  As
>> a separate patch though so this one is easy to backport.
> 
> Agreed, a simple regression test(either selftest or igt) for this would be nice, if possible.
> 
>>
>> Regards,
>>
>> Tvrtko
>>
>>> ---
>>>    drivers/gpu/drm/i915/gem/i915_gem_mman.c | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
>>> b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
>>> index efe69d6b86f4..c3ea243d414d 100644
>>> --- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
>>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
>>> @@ -455,7 +455,7 @@ vm_access(struct vm_area_struct *area, unsigned
>>> long addr,
>>>            return -EACCES;
>>>        addr -= area->vm_start;
>>> -    if (addr >= obj->base.size)
>>> +    if (range_overflows_t(u64, addr, len, obj->base.size))
>>>            return -EINVAL;
> 
> Other users like ttm_bo_vm_access are also checking if len <= 0, should we also add an explicit check for that here? Otherwise LGTM.
> 
> I think no need to add here len<=0,  we already validating same  range_overflows_t . converted following condition to range_overflow_t.
> 
> if (len < 1 || len > obj->base.size ||
>              addr >= obj->base.size ||
>              addr + len > obj->base.size)
> 
>>>        i915_gem_ww_ctx_init(&ww, true);