[PATCH AUTOSEL 5.7 26/60] drm/msm: Fix a null pointer access in msm_gem_shrinker_count()

Sasha Levin
2020-08-10T19:28:43Z

From: Akhil P Oommen <akhilpo@codeaurora.org>

[ Upstream commit 3cbdc8d8b7f39a7af3ea7b8dfa75caaebfda4e56 ]

Adding an msm_gem_object object to the inactive_list before completing
its initialization is a bad idea because shrinker may pick it up from the
inactive_list. Fix this by making sure that the initialization is complete
before moving the msm_obj object to the inactive list.

This patch fixes the below error:
[10027.553044] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000068
[10027.573305] Mem abort info:
[10027.590160] ESR = 0x96000006
[10027.597905] EC = 0x25: DABT (current EL), IL = 32 bits
[10027.614430] SET = 0, FnV = 0
[10027.624427] EA = 0, S1PTW = 0
[10027.632722] Data abort info:
[10027.638039] ISV = 0, ISS = 0x00000006
[10027.647459] CM = 0, WnR = 0
[10027.654345] user pgtable: 4k pages, 39-bit VAs, pgdp=00000001e3a6a000
[10027.672681] [0000000000000068] pgd=0000000198c31003, pud=0000000198c31003, pmd=0000000000000000
[10027.693900] Internal error: Oops: 96000006 [#1] PREEMPT SMP
[10027.738261] CPU: 3 PID: 214 Comm: kswapd0 Tainted: G S 5.4.40 #1
[10027.745766] Hardware name: Qualcomm Technologies, Inc. SC7180 IDP (DT)
[10027.752472] pstate: 80c00009 (Nzcv daif +PAN +UAO)
[10027.757409] pc : mutex_is_locked+0x14/0x2c
[10027.761626] lr : msm_gem_shrinker_count+0x70/0xec
[10027.766454] sp : ffffffc011323ad0
[10027.769867] x29: ffffffc011323ad0 x28: ffffffe677e4b878
[10027.775324] x27: 0000000000000cc0 x26: 0000000000000000
[10027.780783] x25: ffffff817114a708 x24: 0000000000000008
[10027.786242] x23: ffffff8023ab7170 x22: 0000000000000001
[10027.791701] x21: ffffff817114a080 x20: 0000000000000119
[10027.797160] x19: 0000000000000068 x18: 00000000000003bc
[10027.802621] x17: 0000000004a34210 x16: 00000000000000c0
[10027.808083] x15: 0000000000000000 x14: 0000000000000000
[10027.813542] x13: ffffffe677e0a3c0 x12: 0000000000000000
[10027.819000] x11: 0000000000000000 x10: ffffff8174b94340
[10027.824461] x9 : 0000000000000000 x8 : 0000000000000000
[10027.829919] x7 : 00000000000001fc x6 : ffffffc011323c88
[10027.835373] x5 : 0000000000000001 x4 : ffffffc011323d80
[10027.840832] x3 : ffffffff0477b348 x2 : 0000000000000000
[10027.846290] x1 : ffffffc011323b68 x0 : 0000000000000068
[10027.851748] Call trace:
[10027.854264] mutex_is_locked+0x14/0x2c
[10027.858121] msm_gem_shrinker_count+0x70/0xec
[10027.862603] shrink_slab+0xc0/0x4b4
[10027.866187] shrink_node+0x4a8/0x818
[10027.869860] kswapd+0x624/0x890
[10027.873097] kthread+0x11c/0x12c
[10027.876424] ret_from_fork+0x10/0x18
[10027.880102] Code: f9000bf3 910003fd aa0003f3 d503201f (f9400268)
[10027.886362] ---[ end trace df5849a1a3543251 ]---
[10027.891518] Kernel panic - not syncing: Fatal exception

Signed-off-by: Akhil P Oommen <akhilpo@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/msm/msm_gem.c | 36 ++++++++++++++++++++---------------
1 file changed, 21 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index 5a6a79fbc9d6e..d92a0ffe2a767 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -977,10 +977,8 @@ int msm_gem_new_handle(struct drm_device *dev, struct drm_file *file,

static int msm_gem_new_impl(struct drm_device *dev,
uint32_t size, uint32_t flags,
- struct drm_gem_object **obj,
- bool struct_mutex_locked)
+ struct drm_gem_object **obj)
{
- struct msm_drm_private *priv = dev->dev_private;
struct msm_gem_object *msm_obj;

switch (flags & MSM_BO_CACHE_MASK) {
@@ -1006,15 +1004,6 @@ static int msm_gem_new_impl(struct drm_device *dev,
INIT_LIST_HEAD(&msm_obj->submit_entry);
INIT_LIST_HEAD(&msm_obj->vmas);

- if (struct_mutex_locked) {
- WARN_ON(!mutex_is_locked(&dev->struct_mutex));
- list_add_tail(&msm_obj->mm_list, &priv->inactive_list);
- } else {
- mutex_lock(&dev->struct_mutex);
- list_add_tail(&msm_obj->mm_list, &priv->inactive_list);
- mutex_unlock(&dev->struct_mutex);
- }
-
*obj = &msm_obj->base;

return 0;
@@ -1024,6 +1013,7 @@ static struct drm_gem_object *_msm_gem_new(struct drm_device *dev,
uint32_t size, uint32_t flags, bool struct_mutex_locked)
{
struct msm_drm_private *priv = dev->dev_private;
+ struct msm_gem_object *msm_obj;
struct drm_gem_object *obj = NULL;
bool use_vram = false;
int ret;
@@ -1044,14 +1034,15 @@ static struct drm_gem_object *_msm_gem_new(struct drm_device *dev,
if (size == 0)
return ERR_PTR(-EINVAL);

- ret = msm_gem_new_impl(dev, size, flags, &obj, struct_mutex_locked);
+ ret = msm_gem_new_impl(dev, size, flags, &obj);
if (ret)
goto fail;

+ msm_obj = to_msm_bo(obj);
+
if (use_vram) {
struct msm_gem_vma *vma;
struct page **pages;
- struct msm_gem_object *msm_obj = to_msm_bo(obj);

mutex_lock(&msm_obj->lock);

@@ -1086,6 +1077,15 @@ static struct drm_gem_object *_msm_gem_new(struct drm_device *dev,
mapping_set_gfp_mask(obj->filp->f_mapping, GFP_HIGHUSER);
}

+ if (struct_mutex_locked) {
+ WARN_ON(!mutex_is_locked(&dev->struct_mutex));
+ list_add_tail(&msm_obj->mm_list, &priv->inactive_list);
+ } else {
+ mutex_lock(&dev->struct_mutex);
+ list_add_tail(&msm_obj->mm_list, &priv->inactive_list);
+ mutex_unlock(&dev->struct_mutex);
+ }
+
return obj;

fail:
@@ -1108,6 +1108,7 @@ struct drm_gem_object *msm_gem_new(struct drm_device *dev,
struct drm_gem_object *msm_gem_import(struct drm_device *dev,
struct dma_buf *dmabuf, struct sg_table *sgt)
{
+ struct msm_drm_private *priv = dev->dev_private;
struct msm_gem_object *msm_obj;
struct drm_gem_object *obj;
uint32_t size;
@@ -1121,7 +1122,7 @@ struct drm_gem_object *msm_gem_import(struct drm_device *dev,

size = PAGE_ALIGN(dmabuf->size);

- ret = msm_gem_new_impl(dev, size, MSM_BO_WC, &obj, false);
+ ret = msm_gem_new_impl(dev, size, MSM_BO_WC, &obj);
if (ret)
goto fail;

@@ -1146,6 +1147,11 @@ struct drm_gem_object *msm_gem_import(struct drm_device *dev,
}

mutex_unlock(&msm_obj->lock);
+
+ mutex_lock(&dev->struct_mutex);
+ list_add_tail(&msm_obj->mm_list, &priv->inactive_list);
+ mutex_unlock(&dev->struct_mutex);
+
return obj;

fail:
--
2.25.1