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

[Tvrtko Ursulin]

+ 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 at intel.com>
> Suggested-by: Adam Zabrocki <adamza at microsoft.com>
> Reported-by: Jackson Cody <cody.jackson at intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Bloomfield Jon <jon.bloomfield at intel.com>
> Cc: Dutt Sudeep <sudeep.dutt at intel.com>

Fixes: 9f909e215fea ("drm/i915: Implement vm_ops->access for gdb access into mmaps")
Cc: <stable at 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.

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;
>   
>   	i915_gem_ww_ctx_init(&ww, true);