linux-kernel - [PATCH 1/2] drm/msm: Fix null dereference in _msm_gem

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Message-Id: <20201228213131.2316293-1-iskren.chernev@gmail.com>
Date:   Mon, 28 Dec 2020 23:31:30 +0200
From:   Iskren Chernev <iskren.chernev@...il.com>
To:     Rob Clark <robdclark@...il.com>
Cc:     Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        "Kristian H . Kristensen" <hoegsberg@...gle.com>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        ~postmarketos/upstreaming@...ts.sr.ht,
        Iskren Chernev <iskren.chernev@...il.com>
Subject: [PATCH 1/2] drm/msm: Fix null dereference in _msm_gem_new

The crash was caused by locking an uninitialized lock during init of
drm_gem_object. The lock changed in the breaking commit, but the init
was not moved accordingly.

 8<--- cut here ---
 Unable to handle kernel NULL pointer dereference at virtual address 00000000
 pgd = (ptrval)
 [00000000] *pgd=00000000
 Internal error: Oops: 5 [#1] PREEMPT SMP ARM
 Modules linked in: msm(+) qcom_spmi_vadc qcom_vadc_common dm_mod usb_f_rndis rmi_i2c rmi_core qnoc_msm8974 icc_smd_rpm pm8941_pwrkey
 CPU: 2 PID: 1020 Comm: udevd Not tainted 5.10.0-postmarketos-qcom-msm8974 #8
 Hardware name: Generic DT based system
 PC is at ww_mutex_lock+0x20/0xb0
 LR is at _msm_gem_new+0x13c/0x298 [msm]
 pc : [<c0be31e8>]    lr : [<bf0b3404>]    psr: 20000013
 sp : c36e7ad0  ip : c3b3d800  fp : 00000000
 r10: 00000001  r9 : c3b22800  r8 : 00000000
 r7 : c3b23000  r6 : c3b3d600  r5 : c3b3d600  r4 : 00000000
 r3 : c34b4780  r2 : c3b3d6f4  r1 : 00000000  r0 : 00000000
 Flags: nzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
 Control: 10c5787d  Table: 03ae406a  DAC: 00000051
 Process udevd (pid: 1020, stack limit = 0x(ptrval))
 Stack: (0xc36e7ad0 to 0xc36e8000)
 [...]
 [<c0be31e8>] (ww_mutex_lock) from [<bf0b3404>] (_msm_gem_new+0x13c/0x298 [msm])
 [<bf0b3404>] (_msm_gem_new [msm]) from [<bf0b3aa8>] (_msm_gem_kernel_new+0x20/0x190 [msm])
 [<bf0b3aa8>] (_msm_gem_kernel_new [msm]) from [<bf0b4a30>] (msm_gem_kernel_new+0x24/0x2c [msm])
 [<bf0b4a30>] (msm_gem_kernel_new [msm]) from [<bf0b8e2c>] (msm_gpu_init+0x308/0x548 [msm])
 [<bf0b8e2c>] (msm_gpu_init [msm]) from [<bf060a90>] (adreno_gpu_init+0x13c/0x240 [msm])
 [<bf060a90>] (adreno_gpu_init [msm]) from [<bf062b1c>] (a3xx_gpu_init+0x78/0x1dc [msm])
 [<bf062b1c>] (a3xx_gpu_init [msm]) from [<bf05f394>] (adreno_bind+0x1cc/0x274 [msm])
 [<bf05f394>] (adreno_bind [msm]) from [<c087a254>] (component_bind_all+0x11c/0x278)
 [<c087a254>] (component_bind_all) from [<bf0b11d4>] (msm_drm_bind+0x18c/0x5b4 [msm])
 [<bf0b11d4>] (msm_drm_bind [msm]) from [<c0879ea0>] (try_to_bring_up_master+0x200/0x2c8)
 [<c0879ea0>] (try_to_bring_up_master) from [<c087a648>] (component_master_add_with_match+0xc8/0xfc)
 [<c087a648>] (component_master_add_with_match) from [<bf0b0c3c>] (msm_pdev_probe+0x288/0x2c4 [msm])
 [<bf0b0c3c>] (msm_pdev_probe [msm]) from [<c08844cc>] (platform_drv_probe+0x48/0x98)
 [<c08844cc>] (platform_drv_probe) from [<c0881cc4>] (really_probe+0x108/0x528)
 [<c0881cc4>] (really_probe) from [<c0882480>] (driver_probe_device+0x78/0x1d4)
 [<c0882480>] (driver_probe_device) from [<c08828dc>] (device_driver_attach+0xa8/0xb0)
 [<c08828dc>] (device_driver_attach) from [<c0882998>] (__driver_attach+0xb4/0x154)
 [<c0882998>] (__driver_attach) from [<c087fa1c>] (bus_for_each_dev+0x78/0xb8)
 [<c087fa1c>] (bus_for_each_dev) from [<c0880e98>] (bus_add_driver+0x10c/0x208)
 [<c0880e98>] (bus_add_driver) from [<c0883504>] (driver_register+0x88/0x118)
 [<c0883504>] (driver_register) from [<c0302098>] (do_one_initcall+0x50/0x2b0)
 [<c0302098>] (do_one_initcall) from [<c03bace4>] (do_init_module+0x60/0x288)
 [<c03bace4>] (do_init_module) from [<c03bdf1c>] (sys_finit_module+0xd4/0x120)
 [<c03bdf1c>] (sys_finit_module) from [<c0300060>] (ret_fast_syscall+0x0/0x54)
 Exception stack(0xc36e7fa8 to 0xc36e7ff0)
 7fa0:                   00020000 00000000 00000007 b6edd5b0 00000000 b6f2ff20
 7fc0: 00020000 00000000 0000017b 0000017b b6eef980 bedc3a54 00473c99 00000000
 7fe0: b6edd5b0 bedc3918 b6ed8a5f b6f6a8b0
 Code: e3c3303f e593300c e1a04000 f590f000 (e1940f9f)
 ---[ end trace 277e2a3da40bbb76 ]---

Fixes: 6c0e3ea250476 ("drm/msm/gem: Switch over to obj->resv for locking")
Signed-off-by: Iskren Chernev <iskren.chernev@...il.com>
---
 drivers/gpu/drm/msm/msm_gem.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index 32d5c514e28ad..c658deb31eb5d 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -1116,6 +1116,8 @@ static struct drm_gem_object *_msm_gem_new(struct drm_device *dev,
 		struct msm_gem_vma *vma;
 		struct page **pages;
 
+		drm_gem_private_object_init(dev, obj, size);
+
 		msm_gem_lock(obj);
 
 		vma = add_vma(obj, NULL);
@@ -1127,7 +1129,6 @@ static struct drm_gem_object *_msm_gem_new(struct drm_device *dev,
 
 		to_msm_bo(obj)->vram_node = &vma->node;
 
-		drm_gem_private_object_init(dev, obj, size);
 
 		pages = get_pages(obj);
 		if (IS_ERR(pages)) {

base-commit: d7a03a44a5e93f39ece70ec75d25c6088caa0fdb
-- 
2.29.2