drm/i915/gem: add missing boundary check in vm_access

In the Linux kernel, the following vulnerability has been resolved:

drm/i915/gem: add missing boundary check in vm_access

A missing bounds check in vm_access() can lead to an out-of-bounds read
or write in the adjacent memory area, since the len attribute is not
validated before the memcpy later in the function, potentially hitting:

[ 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

Changes since v1:
- Updated if condition with range_overflows_t [Chris Wilson]

[mauld: tidy up the commit message and add Cc: stable]
(cherry picked from commit 661412e301e2ca86799aa4f400d1cf0bd38c57c6)