Some users want to pass NULL to drm_gem_object_put(), but those using
__drm_gem_object_put() did not. Compromise, have both and let the
compiler sort it out.
drm_gem_fb_destroy() calls drm_gem_object_put() with NULL obj causing:
[ 11.584209] BUG: kernel NULL pointer dereference, address: 0000000000000000
[ 11.584213] #PF: supervisor write access in kernel mode
[ 11.584215] #PF: error_code(0x0002) - not-present page
[ 11.584216] PGD 0 P4D 0
[ 11.584220] Oops: 0002 [#1] SMP NOPTI
[ 11.584223] CPU: 7 PID: 1571 Comm: gnome-shell Tainted: G E 5.7.0-rc1-1-default+ #27
[ 11.584225] Hardware name: Micro-Star International Co., Ltd. MS-7A31/X370 XPOWER GAMING TITANIUM (MS-7A31), BIOS 1.MR 12/03/2019
[ 11.584237] RIP: 0010:drm_gem_fb_destroy+0x28/0x70 [drm_kms_helper]
<snip>
[ 11.584256] Call Trace:
[ 11.584279] drm_mode_rmfb+0x189/0x1c0 [drm]
[ 11.584299] ? drm_mode_rmfb+0x1c0/0x1c0 [drm]
[ 11.584314] drm_ioctl_kernel+0xaa/0xf0 [drm]
[ 11.584329] drm_ioctl+0x1ff/0x3b0 [drm]
[ 11.584347] ? drm_mode_rmfb+0x1c0/0x1c0 [drm]
[ 11.584421] amdgpu_drm_ioctl+0x49/0x80 [amdgpu]
[ 11.584427] ksys_ioctl+0x87/0xc0
[ 11.584430] __x64_sys_ioctl+0x16/0x20
[ 11.584434] do_syscall_64+0x5f/0x240
[ 11.584438] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 11.584440] RIP: 0033:0x7f0ef80f7227
Reported-by: Nirmoy Das <nirmoy.das@xxxxxxx>
Fixes: b5d250744ccc ("drm/gem: fold drm_gem_object_put_unlocked and __drm_gem_object_put()")
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Nirmoy Das <nirmoy.das@xxxxxxx>
Cc: Emil Velikov <emil.velikov@xxxxxxxxxxxxx>
Cc: Christian König <christian.koenig@xxxxxxx>.
Acked-by: Nirmoy Das <nirmoy.das@xxxxxxx>
---
drivers/gpu/drm/i915/gem/i915_gem_object.h | 2 +-
include/drm/drm_gem.h | 10 +++++++++-
2 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
index aba7517c2837..2faa481cc18f 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
@@ -105,7 +105,7 @@ __attribute__((nonnull))
static inline void
i915_gem_object_put(struct drm_i915_gem_object *obj)
{
- drm_gem_object_put(&obj->base);
+ __drm_gem_object_put(&obj->base);
}
#define assert_object_held(obj) dma_resv_assert_held((obj)->base.resv)
diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
index 52173abdf500..2410ff0a8e86 100644
--- a/include/drm/drm_gem.h
+++ b/include/drm/drm_gem.h
@@ -363,6 +363,13 @@ static inline void drm_gem_object_get(struct drm_gem_object *obj)
kref_get(&obj->refcount);
}
+__attribute__((nonnull))
+static inline void
+__drm_gem_object_put(struct drm_gem_object *obj)
+{
+ kref_put(&obj->refcount, drm_gem_object_free);
+}
+
/**
* drm_gem_object_put - drop a GEM buffer object reference
* @obj: GEM buffer object
@@ -372,7 +379,8 @@ static inline void drm_gem_object_get(struct drm_gem_object *obj)
static inline void
drm_gem_object_put(struct drm_gem_object *obj)
{
- kref_put(&obj->refcount, drm_gem_object_free);
+ if (obj)
+ __drm_gem_object_put(obj);
}
void drm_gem_object_put_locked(struct drm_gem_object *obj);
--
2.20.1
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