drm/msm: Fix NULL pointer dereference

drm/msm: Fix NULL pointer dereference

[    3.707412] Unable to handle kernel NULL pointer dereference at virtual address 0000009c
[    3.714511] pgd = (ptrval)
[    3.722742] [0000009c] *pgd=00000000
[    3.725238] Internal error: Oops: 5 [#1] PREEMPT SMP ARM
[    3.728968] Modules linked in:
[    3.734265] CPU: 3 PID: 112 Comm: kworker/3:2 Tainted: G        W         5.0.0-rc7-00183-g06a1c31df9eb #4
[    3.737142] Hardware name: Generic DT based system
[    3.746778] Workqueue: events deferred_probe_work_func
[    3.751542] PC is at msm_gem_map_vma+0x3c/0xac
[    3.756669] LR is at msm_gem_get_and_pin_iova+0xd8/0x134
[    3.761086] pc : [<c07d3b7c>]    lr : [<c07d14f8>]    psr: 60000013
[    3.766560] sp : ee297be8  ip : ed9ab1c0  fp : ed93b800
[    3.772546] r10: ee35e180  r9 : 00000000  r8 : ee297c80
[    3.777752] r7 : 00000000  r6 : 7c100000  r5 : 00000000  r4 : ee35e180
[    3.782968] r3 : 00000001  r2 : 00000003  r1 : ee35e180  r0 : 00000000
[    3.789562] Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
[    3.796079] Control: 10c5787d  Table: 2e3a806a  DAC: 00000051
[    3.803282] Process kworker/3:2 (pid: 112, stack limit = 0x(ptrval))
[    3.809006] Stack: (0xee297be8 to 0xee298000)
[    3.815445] 7be0:                   00000000 c1108c48 eda8c000 00000003 eda8c0fc c1108c48
[    3.819715] 7c00: eda8c000 00000003 eda8c0fc c07d14f8 00000001 c07d1100 7c100000 00000000
[    3.827873] 7c20: eda8c000 bb7ffb78 00000000 eda8c000 00000000 00000000 c0c8b1d4 ee3bfa00
[    3.836037] 7c40: ee3b9800 c07d1684 00000000 c1108c48 ee0d7810 ee3b9800 c0c8b1d4 c07d222c
[    3.844193] 7c60: ee3bfd84 ee297c80 00000000 c0b1d5b0 ee3bfc40 c07dcfd8 ee3bfd84 ee297c80
[    3.852357] 7c80: 0000006d ee3bfc40 ee0d7810 bb7ffb78 c0c8b1d4 00000000 ee3bfc40 c07ddb48
[    3.860516] 7ca0: 00002004 c0eba384 ee3bfc40 c079eba0 ee3bd040 ee3b9800 00000001 ed93b800
[    3.868673] 7cc0: ed9aa100 c07db7e8 ee3bf240 ed9a6500 00000001 ee3b9800 ee3bf2d4 c07a0a30
[    3.876834] 7ce0: ed93b800 7d100000 c1108c48 ee0d7610 ee3b9800 ed93b800 c1108c48 00000000
[    3.884991] 7d00: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[    3.893151] 7d20: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 bb7ffb78
[    3.901310] 7d40: c12113c4 ed93b800 ee3b9800 c1108c48 ee9eec10 00000000 ed93b800 7d100000
[    3.909472] 7d60: eff7b000 c07cf748 7d100000 00000000 c0e9a350 c0b1d5b0 c12113c4 c0961e40
[    3.917633] 7d80: c12113c4 40000113 eeff4bec c0ebe004 00000019 c0b1d230 ee9eeda8 60000113
[    3.925791] 7da0: ee35d300 ee9eeda8 c07ce260 bb7ffb78 c07ce260 ee35d2c0 00000028 00000002
[    3.933950] 7dc0: eeb76280 c118f884 ee0be640 c11c6128 c07ce260 c07ea4ac 00000000 c0962b48
[    3.942108] 7de0: c118f868 00000001 c0ebbc98 ee35d2c0 00000000 eeb76280 00000000 c118f87c
[    3.950270] 7e00: ee35d2c0 00000000 c11c63e0 c118f694 00000019 c07ea5d0 ee0d7810 00000000
[    3.958430] 7e20: c118f694 00000000 00000000 c07f2b0c c120f55c ee0d7810 c120f560 00000000
[    3.966590] 7e40: 00000000 c07f08c4 c07f0e8c ee0d7810 c11ba3d0 ee0d7810 c118f694 c07f0e8c
[    3.974748] 7e60: c1108c48 00000001 c0ebc3cc c11c63f8 c11ba3d0 c07f0c08 00000001 c07f2f8c
[    3.982908] 7e80: c118f694 00000000 ee297ed4 c07f0e8c c1108c48 00000001 c0ebc3cc c11c63f8
[    3.991068] 7ea0: c11ba3d0 c07ee8a0 c11ba3d0 ee82686c ee0baf38 bb7ffb78 ee0d7810 ee0d7810
[    3.999227] 7ec0: c1108c48 ee0d7844 c118faac c07f05b0 ee0d7810 ee0d7810 00000001 bb7ffb78
[    4.007389] 7ee0: ee0d7810 ee0d7810 c118fd18 c118faac c11c63e0 c07ef7d0 ee0d7810 c118fa90
[    4.015548] 7f00: c118fa90 c07efd68 c118fac8 ee27fe00 eefd9c80 eefdcd00 00000000 c118facc
[    4.023708] 7f20: 00000000 c033c038 eefd9c80 eefd9c80 00000008 ee27fe00 ee27fe14 eefd9c80
[    4.031866] 7f40: 00000008 c1103d00 eefd9c98 ee296000 eefd9c80 c033ce54 ee907eac c0b1d230
[    4.040026] 7f60: ee907eac eea24440 ee285000 00000000 ee296000 ee27fe00 c033ce24 eea2445c
[    4.048188] 7f80: ee907eac c0341db0 00000000 ee285000 c0341c8c 00000000 00000000 00000000
[    4.056346] 7fa0: 00000000 00000000 00000000 c03010e8 00000000 00000000 00000000 00000000
[    4.064505] 7fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[    4.072665] 7fe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
[    4.080828] [<c07d3b7c>] (msm_gem_map_vma) from [<c07d14f8>] (msm_gem_get_and_pin_iova+0xd8/0x134)
[    4.088983] [<c07d14f8>] (msm_gem_get_and_pin_iova) from [<c07d1684>] (_msm_gem_kernel_new+0x38/0xac)
[    4.097839] [<c07d1684>] (_msm_gem_kernel_new) from [<c07d222c>] (msm_gem_kernel_new+0x24/0x2c)
[    4.107130] [<c07d222c>] (msm_gem_kernel_new) from [<c07dcfd8>] (dsi_tx_buf_alloc_6g+0x44/0x90)
[    4.115631] [<c07dcfd8>] (dsi_tx_buf_alloc_6g) from [<c07ddb48>] (msm_dsi_host_modeset_init+0x80/0x104)
[    4.124313] [<c07ddb48>] (msm_dsi_host_modeset_init) from [<c07db7e8>] (msm_dsi_modeset_init+0x34/0x1c0)
[    4.133691] [<c07db7e8>] (msm_dsi_modeset_init) from [<c07a0a30>] (mdp5_kms_init+0x764/0x7e0)
[    4.143409] [<c07a0a30>] (mdp5_kms_init) from [<c07cf748>] (msm_drm_bind+0x56c/0x740)
[    4.151824] [<c07cf748>] (msm_drm_bind) from [<c07ea4ac>] (try_to_bring_up_master+0x238/0x2b4)
[    4.159636] [<c07ea4ac>] (try_to_bring_up_master) from [<c07ea5d0>] (component_add+0xa8/0x170)
[    4.168146] [<c07ea5d0>] (component_add) from [<c07f2b0c>] (platform_drv_probe+0x48/0x9c)
[    4.176737] [<c07f2b0c>] (platform_drv_probe) from [<c07f08c4>] (really_probe+0x278/0x404)
[    4.184981] [<c07f08c4>] (really_probe) from [<c07f0c08>] (driver_probe_device+0x78/0x1c0)
[    4.193147] [<c07f0c08>] (driver_probe_device) from [<c07ee8a0>] (bus_for_each_drv+0x74/0xb8)
[    4.201389] [<c07ee8a0>] (bus_for_each_drv) from [<c07f05b0>] (__device_attach+0xd0/0x164)
[    4.209984] [<c07f05b0>] (__device_attach) from [<c07ef7d0>] (bus_probe_device+0x84/0x8c)
[    4.218143] [<c07ef7d0>] (bus_probe_device) from [<c07efd68>] (deferred_probe_work_func+0x48/0xc4)
[    4.226398] [<c07efd68>] (deferred_probe_work_func) from [<c033c038>] (process_one_work+0x204/0x574)
[    4.235254] [<c033c038>] (process_one_work) from [<c033ce54>] (worker_thread+0x30/0x560)
[    4.244534] [<c033ce54>] (worker_thread) from [<c0341db0>] (kthread+0x124/0x154)
[    4.252606] [<c0341db0>] (kthread) from [<c03010e8>] (ret_from_fork+0x14/0x2c)
[    4.259966] Exception stack(0xee297fb0 to 0xee297ff8)
[    4.266998] 7fa0:                                     00000000 00000000 00000000 00000000
[    4.272143] 7fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[    4.280297] 7fe0: 00000000 00000000 00000000 00000000 00000013 00000000
[    4.288451] Code: e5813080 1a000013 e3a03001 e5c4307c (e590009c)
[    4.294933] ---[ end trace 18729cc2bca2b4b3 ]---

Signed-off-by: Luca Weiss <luca@z3ntu.xyz>
Signed-off-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Rob Clark <robdclark@chromium.org>