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[PATCH v2] drm/panic: Fix uninitialized spinlock acquisition with CONFIG_DRM_PANIC=n

Lyude Paul posted 1 patch 2 months, 1 week ago 
drivers/gpu/drm/drm_atomic_helper.c |  2 +-
include/drm/drm_panic.h             | 14 ++++++++++++++
2 files changed, 15 insertions(+), 1 deletion(-)
[PATCH v2] drm/panic: Fix uninitialized spinlock acquisition with CONFIG_DRM_PANIC=n
Posted by Lyude Paul 2 months, 1 week ago 
It turns out that if you happen to have a kernel config where
CONFIG_DRM_PANIC is disabled and spinlock debugging is enabled, along with
KMS being enabled - we'll end up trying to acquire an uninitialized
spin_lock with drm_panic_lock() when we try to do a commit:

  rvkms rvkms.0: [drm:drm_atomic_commit] committing 0000000068d2ade1
  INFO: trying to register non-static key.
  The code is fine but needs lockdep annotation, or maybe
  you didn't initialize this object before use?
  turning off the locking correctness validator.
  CPU: 4 PID: 1347 Comm: modprobe Not tainted 6.10.0-rc1Lyude-Test+ #272
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS edk2-20240524-3.fc40 05/24/2024
  Call Trace:
   <TASK>
   dump_stack_lvl+0x77/0xa0
   assign_lock_key+0x114/0x120
   register_lock_class+0xa8/0x2c0
   __lock_acquire+0x7d/0x2bd0
   ? __vmap_pages_range_noflush+0x3a8/0x550
   ? drm_atomic_helper_swap_state+0x2ad/0x3a0
   lock_acquire+0xec/0x290
   ? drm_atomic_helper_swap_state+0x2ad/0x3a0
   ? lock_release+0xee/0x310
   _raw_spin_lock_irqsave+0x4e/0x70
   ? drm_atomic_helper_swap_state+0x2ad/0x3a0
   drm_atomic_helper_swap_state+0x2ad/0x3a0
   drm_atomic_helper_commit+0xb1/0x270
   drm_atomic_commit+0xaf/0xe0
   ? __pfx___drm_printfn_info+0x10/0x10
   drm_client_modeset_commit_atomic+0x1a1/0x250
   drm_client_modeset_commit_locked+0x4b/0x180
   drm_client_modeset_commit+0x27/0x50
   __drm_fb_helper_restore_fbdev_mode_unlocked+0x76/0x90
   drm_fb_helper_set_par+0x38/0x40
   fbcon_init+0x3c4/0x690
   visual_init+0xc0/0x120
   do_bind_con_driver+0x409/0x4c0
   do_take_over_console+0x233/0x280
   do_fb_registered+0x11f/0x210
   fbcon_fb_registered+0x2c/0x60
   register_framebuffer+0x248/0x2a0
   __drm_fb_helper_initial_config_and_unlock+0x58a/0x720
   drm_fbdev_generic_client_hotplug+0x6e/0xb0
   drm_client_register+0x76/0xc0
   _RNvXs_CsHeezP08sTT_5rvkmsNtB4_5RvkmsNtNtCs1cdwasc6FUb_6kernel8platform6Driver5probe+0xed2/0x1060 [rvkms]
   ? _RNvMs_NtCs1cdwasc6FUb_6kernel8platformINtB4_7AdapterNtCsHeezP08sTT_5rvkms5RvkmsE14probe_callbackBQ_+0x2b/0x70 [rvkms]
   ? acpi_dev_pm_attach+0x25/0x110
   ? platform_probe+0x6a/0xa0
   ? really_probe+0x10b/0x400
   ? __driver_probe_device+0x7c/0x140
   ? driver_probe_device+0x22/0x1b0
   ? __device_attach_driver+0x13a/0x1c0
   ? __pfx___device_attach_driver+0x10/0x10
   ? bus_for_each_drv+0x114/0x170
   ? __device_attach+0xd6/0x1b0
   ? bus_probe_device+0x9e/0x120
   ? device_add+0x288/0x4b0
   ? platform_device_add+0x75/0x230
   ? platform_device_register_full+0x141/0x180
   ? rust_helper_platform_device_register_simple+0x85/0xb0
   ? _RNvMs2_NtCs1cdwasc6FUb_6kernel8platformNtB5_6Device13create_simple+0x1d/0x60
   ? _RNvXs0_CsHeezP08sTT_5rvkmsNtB5_5RvkmsNtCs1cdwasc6FUb_6kernel6Module4init+0x11e/0x160 [rvkms]
   ? 0xffffffffc083f000
   ? init_module+0x20/0x1000 [rvkms]
   ? kernfs_xattr_get+0x3e/0x80
   ? do_one_initcall+0x148/0x3f0
   ? __lock_acquire+0x5ef/0x2bd0
   ? __lock_acquire+0x5ef/0x2bd0
   ? __lock_acquire+0x5ef/0x2bd0
   ? put_cpu_partial+0x51/0x1d0
   ? lock_acquire+0xec/0x290
   ? put_cpu_partial+0x51/0x1d0
   ? lock_release+0xee/0x310
   ? put_cpu_partial+0x51/0x1d0
   ? fs_reclaim_acquire+0x69/0xf0
   ? lock_acquire+0xec/0x290
   ? fs_reclaim_acquire+0x69/0xf0
   ? kfree+0x22f/0x340
   ? lock_release+0xee/0x310
   ? kmalloc_trace_noprof+0x48/0x340
   ? do_init_module+0x22/0x240
   ? kmalloc_trace_noprof+0x155/0x340
   ? do_init_module+0x60/0x240
   ? __se_sys_finit_module+0x2e0/0x3f0
   ? do_syscall_64+0xa4/0x180
   ? syscall_exit_to_user_mode+0x108/0x140
   ? do_syscall_64+0xb0/0x180
   ? vma_end_read+0xd0/0xe0
   ? do_user_addr_fault+0x309/0x640
   ? clear_bhb_loop+0x45/0xa0
   ? clear_bhb_loop+0x45/0xa0
   ? clear_bhb_loop+0x45/0xa0
   ? entry_SYSCALL_64_after_hwframe+0x76/0x7e
   </TASK>

Fix this by stubbing these macros out when this config option isn't
enabled, along with fixing the unused variable warning that introduces.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Fixes: e2a1cda3e0c7 ("drm/panic: Add drm panic locking")
Cc: <stable@vger.kernel.org> # v6.10+

---

V2:
* Use static inline instead of macros so we don't need
  __maybe_unused

---
 drivers/gpu/drm/drm_atomic_helper.c |  2 +-
 include/drm/drm_panic.h             | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 43cdf39019a44..5186d2114a503 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -3015,7 +3015,7 @@ int drm_atomic_helper_swap_state(struct drm_atomic_state *state,
 				  bool stall)
 {
 	int i, ret;
-	unsigned long flags;
+	unsigned long flags = 0;
 	struct drm_connector *connector;
 	struct drm_connector_state *old_conn_state, *new_conn_state;
 	struct drm_crtc *crtc;
diff --git a/include/drm/drm_panic.h b/include/drm/drm_panic.h
index 54085d5d05c34..f4e1fa9ae607a 100644
--- a/include/drm/drm_panic.h
+++ b/include/drm/drm_panic.h
@@ -64,6 +64,8 @@ struct drm_scanout_buffer {
 
 };
 
+#ifdef CONFIG_DRM_PANIC
+
 /**
  * drm_panic_trylock - try to enter the panic printing critical section
  * @dev: struct drm_device
@@ -149,4 +151,16 @@ struct drm_scanout_buffer {
 #define drm_panic_unlock(dev, flags) \
 	raw_spin_unlock_irqrestore(&(dev)->mode_config.panic_lock, flags)
 
+#else
+
+static inline bool drm_panic_trylock(struct drm_device *dev, unsigned long flags)
+{
+	return true;
+}
+
+static inline void drm_panic_lock(struct drm_device *dev, unsigned long flags) {}
+static inline void drm_panic_unlock(struct drm_device *dev, unsigned long flags) {}
+
+#endif
+
 #endif /* __DRM_PANIC_H__ */

base-commit: bf05aeac230e390a5aee4bd3dc978b0c4d7e745f
-- 
2.46.0
Re: [PATCH v2] drm/panic: Fix uninitialized spinlock acquisition with CONFIG_DRM_PANIC=n
Posted by Jocelyn Falempe 2 months, 1 week ago 
On 17/09/2024 01:00, Lyude Paul wrote:
> It turns out that if you happen to have a kernel config where
> CONFIG_DRM_PANIC is disabled and spinlock debugging is enabled, along with
> KMS being enabled - we'll end up trying to acquire an uninitialized
> spin_lock with drm_panic_lock() when we try to do a commit:

The raw spinlock should be initialized in drm_dev_init() [1] regardless 
of DRM_PANIC being enabled or not.

 From the call trace, it looks like you are calling 
drm_client_register() before calling drm_dev_register(), and that's 
probably the root cause.

I didn't find a doc saying drm_dev_register() should be done before 
drm_client_register(), but all drivers are doing it this way.

Can you try to do that in rvkms, and see if it fixes this error ?

Best regards,

-- 

Jocelyn

[1] 
https://elixir.bootlin.com/linux/v6.11/source/drivers/gpu/drm/drm_drv.c#L642

> 
>    rvkms rvkms.0: [drm:drm_atomic_commit] committing 0000000068d2ade1
>    INFO: trying to register non-static key.
>    The code is fine but needs lockdep annotation, or maybe
>    you didn't initialize this object before use?
>    turning off the locking correctness validator.
>    CPU: 4 PID: 1347 Comm: modprobe Not tainted 6.10.0-rc1Lyude-Test+ #272
>    Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS edk2-20240524-3.fc40 05/24/2024
>    Call Trace:
>     <TASK>
>     dump_stack_lvl+0x77/0xa0
>     assign_lock_key+0x114/0x120
>     register_lock_class+0xa8/0x2c0
>     __lock_acquire+0x7d/0x2bd0
>     ? __vmap_pages_range_noflush+0x3a8/0x550
>     ? drm_atomic_helper_swap_state+0x2ad/0x3a0
>     lock_acquire+0xec/0x290
>     ? drm_atomic_helper_swap_state+0x2ad/0x3a0
>     ? lock_release+0xee/0x310
>     _raw_spin_lock_irqsave+0x4e/0x70
>     ? drm_atomic_helper_swap_state+0x2ad/0x3a0
>     drm_atomic_helper_swap_state+0x2ad/0x3a0
>     drm_atomic_helper_commit+0xb1/0x270
>     drm_atomic_commit+0xaf/0xe0
>     ? __pfx___drm_printfn_info+0x10/0x10
>     drm_client_modeset_commit_atomic+0x1a1/0x250
>     drm_client_modeset_commit_locked+0x4b/0x180
>     drm_client_modeset_commit+0x27/0x50
>     __drm_fb_helper_restore_fbdev_mode_unlocked+0x76/0x90
>     drm_fb_helper_set_par+0x38/0x40
>     fbcon_init+0x3c4/0x690
>     visual_init+0xc0/0x120
>     do_bind_con_driver+0x409/0x4c0
>     do_take_over_console+0x233/0x280
>     do_fb_registered+0x11f/0x210
>     fbcon_fb_registered+0x2c/0x60
>     register_framebuffer+0x248/0x2a0
>     __drm_fb_helper_initial_config_and_unlock+0x58a/0x720
>     drm_fbdev_generic_client_hotplug+0x6e/0xb0
>     drm_client_register+0x76/0xc0
>     _RNvXs_CsHeezP08sTT_5rvkmsNtB4_5RvkmsNtNtCs1cdwasc6FUb_6kernel8platform6Driver5probe+0xed2/0x1060 [rvkms]
>     ? _RNvMs_NtCs1cdwasc6FUb_6kernel8platformINtB4_7AdapterNtCsHeezP08sTT_5rvkms5RvkmsE14probe_callbackBQ_+0x2b/0x70 [rvkms]
>     ? acpi_dev_pm_attach+0x25/0x110
>     ? platform_probe+0x6a/0xa0
>     ? really_probe+0x10b/0x400
>     ? __driver_probe_device+0x7c/0x140
>     ? driver_probe_device+0x22/0x1b0
>     ? __device_attach_driver+0x13a/0x1c0
>     ? __pfx___device_attach_driver+0x10/0x10
>     ? bus_for_each_drv+0x114/0x170
>     ? __device_attach+0xd6/0x1b0
>     ? bus_probe_device+0x9e/0x120
>     ? device_add+0x288/0x4b0
>     ? platform_device_add+0x75/0x230
>     ? platform_device_register_full+0x141/0x180
>     ? rust_helper_platform_device_register_simple+0x85/0xb0
>     ? _RNvMs2_NtCs1cdwasc6FUb_6kernel8platformNtB5_6Device13create_simple+0x1d/0x60
>     ? _RNvXs0_CsHeezP08sTT_5rvkmsNtB5_5RvkmsNtCs1cdwasc6FUb_6kernel6Module4init+0x11e/0x160 [rvkms]
>     ? 0xffffffffc083f000
>     ? init_module+0x20/0x1000 [rvkms]
>     ? kernfs_xattr_get+0x3e/0x80
>     ? do_one_initcall+0x148/0x3f0
>     ? __lock_acquire+0x5ef/0x2bd0
>     ? __lock_acquire+0x5ef/0x2bd0
>     ? __lock_acquire+0x5ef/0x2bd0
>     ? put_cpu_partial+0x51/0x1d0
>     ? lock_acquire+0xec/0x290
>     ? put_cpu_partial+0x51/0x1d0
>     ? lock_release+0xee/0x310
>     ? put_cpu_partial+0x51/0x1d0
>     ? fs_reclaim_acquire+0x69/0xf0
>     ? lock_acquire+0xec/0x290
>     ? fs_reclaim_acquire+0x69/0xf0
>     ? kfree+0x22f/0x340
>     ? lock_release+0xee/0x310
>     ? kmalloc_trace_noprof+0x48/0x340
>     ? do_init_module+0x22/0x240
>     ? kmalloc_trace_noprof+0x155/0x340
>     ? do_init_module+0x60/0x240
>     ? __se_sys_finit_module+0x2e0/0x3f0
>     ? do_syscall_64+0xa4/0x180
>     ? syscall_exit_to_user_mode+0x108/0x140
>     ? do_syscall_64+0xb0/0x180
>     ? vma_end_read+0xd0/0xe0
>     ? do_user_addr_fault+0x309/0x640
>     ? clear_bhb_loop+0x45/0xa0
>     ? clear_bhb_loop+0x45/0xa0
>     ? clear_bhb_loop+0x45/0xa0
>     ? entry_SYSCALL_64_after_hwframe+0x76/0x7e
>     </TASK>
> 
> Fix this by stubbing these macros out when this config option isn't
> enabled, along with fixing the unused variable warning that introduces.
> 
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Fixes: e2a1cda3e0c7 ("drm/panic: Add drm panic locking")
> Cc: <stable@vger.kernel.org> # v6.10+
> 
> ---
> 
> V2:
> * Use static inline instead of macros so we don't need
>    __maybe_unused
> 
> ---
>   drivers/gpu/drm/drm_atomic_helper.c |  2 +-
>   include/drm/drm_panic.h             | 14 ++++++++++++++
>   2 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 43cdf39019a44..5186d2114a503 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -3015,7 +3015,7 @@ int drm_atomic_helper_swap_state(struct drm_atomic_state *state,
>   				  bool stall)
>   {
>   	int i, ret;
> -	unsigned long flags;
> +	unsigned long flags = 0;
>   	struct drm_connector *connector;
>   	struct drm_connector_state *old_conn_state, *new_conn_state;
>   	struct drm_crtc *crtc;
> diff --git a/include/drm/drm_panic.h b/include/drm/drm_panic.h
> index 54085d5d05c34..f4e1fa9ae607a 100644
> --- a/include/drm/drm_panic.h
> +++ b/include/drm/drm_panic.h
> @@ -64,6 +64,8 @@ struct drm_scanout_buffer {
>   
>   };
>   
> +#ifdef CONFIG_DRM_PANIC
> +
>   /**
>    * drm_panic_trylock - try to enter the panic printing critical section
>    * @dev: struct drm_device
> @@ -149,4 +151,16 @@ struct drm_scanout_buffer {
>   #define drm_panic_unlock(dev, flags) \
>   	raw_spin_unlock_irqrestore(&(dev)->mode_config.panic_lock, flags)
>   
> +#else
> +
> +static inline bool drm_panic_trylock(struct drm_device *dev, unsigned long flags)
> +{
> +	return true;
> +}
> +
> +static inline void drm_panic_lock(struct drm_device *dev, unsigned long flags) {}
> +static inline void drm_panic_unlock(struct drm_device *dev, unsigned long flags) {}
> +
> +#endif
> +
>   #endif /* __DRM_PANIC_H__ */
> 
> base-commit: bf05aeac230e390a5aee4bd3dc978b0c4d7e745f
Re: [PATCH v2] drm/panic: Fix uninitialized spinlock acquisition with CONFIG_DRM_PANIC=n
Posted by Lyude Paul 2 months, 1 week ago 
Eek - sorry, I had already pushed this since it had been reviewed a while ago
and I just forgot to push it afterwards. This being said though - I'm a little
confused here myself. This is correct - drm_client_register was getting called
too early, I wonder if I ran into this before I had moved around the order of
stuff in the KMS init stuff for rust. I will check today and if it fixes the
issue, I'll look at just sending out a revert for review.

On Tue, 2024-09-17 at 09:32 +0200, Jocelyn Falempe wrote:
> On 17/09/2024 01:00, Lyude Paul wrote:
> > It turns out that if you happen to have a kernel config where
> > CONFIG_DRM_PANIC is disabled and spinlock debugging is enabled, along with
> > KMS being enabled - we'll end up trying to acquire an uninitialized
> > spin_lock with drm_panic_lock() when we try to do a commit:
> 
> The raw spinlock should be initialized in drm_dev_init() [1] regardless 
> of DRM_PANIC being enabled or not.
> 
>  From the call trace, it looks like you are calling 
> drm_client_register() before calling drm_dev_register(), and that's 
> probably the root cause.
> 
> I didn't find a doc saying drm_dev_register() should be done before 
> drm_client_register(), but all drivers are doing it this way.
> 
> Can you try to do that in rvkms, and see if it fixes this error ?
> 
> Best regards,
> 

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat

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