* [PATCH] drm/panfrost: Don't dereference bogus MMU pointers
@ 2019-10-28 20:08 ` Robin Murphy
0 siblings, 0 replies; 4+ messages in thread
From: Robin Murphy @ 2019-10-28 20:08 UTC (permalink / raw)
To: robh, tomeu.vizoso; +Cc: steven.price, dri-devel, linux-kernel
It seems that killing an application while faults are occurring
(particularly with a GPU in FPGA at a whopping 40MHz) can lead to
handling a lingering page fault after all the address space contexts
have already been freed. In this situation, the LRU list is empty so
addr_to_drm_mm_node() ends up dereferencing the list head as if it were
a struct panfrost_mmu entry; this leaves "mmu->as" actually pointing at
the pfdev->alloc_mask bitmap, which is also empty, and given that the
fault has a high likelihood of being in AS0, hilarity ensues.
Sadly, the cleanest solution seems to involve another goto. Oh well, at
least it's robust...
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
drivers/gpu/drm/panfrost/panfrost_mmu.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
index e61984e26e0a..508765f80cfe 100644
--- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
+++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
@@ -413,11 +413,11 @@ addr_to_drm_mm_node(struct panfrost_device *pfdev, int as, u64 addr)
spin_lock(&pfdev->as_lock);
list_for_each_entry(mmu, &pfdev->as_lru_list, list) {
if (as == mmu->as)
- break;
+ goto found_mmu;
}
- if (as != mmu->as)
- goto out;
+ goto out;
+found_mmu:
priv = container_of(mmu, struct panfrost_file_priv, mmu);
spin_lock(&priv->mm_lock);
--
2.21.0.dirty
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH] drm/panfrost: Don't dereference bogus MMU pointers
@ 2019-10-28 20:08 ` Robin Murphy
0 siblings, 0 replies; 4+ messages in thread
From: Robin Murphy @ 2019-10-28 20:08 UTC (permalink / raw)
To: robh, tomeu.vizoso; +Cc: linux-kernel, dri-devel, steven.price
It seems that killing an application while faults are occurring
(particularly with a GPU in FPGA at a whopping 40MHz) can lead to
handling a lingering page fault after all the address space contexts
have already been freed. In this situation, the LRU list is empty so
addr_to_drm_mm_node() ends up dereferencing the list head as if it were
a struct panfrost_mmu entry; this leaves "mmu->as" actually pointing at
the pfdev->alloc_mask bitmap, which is also empty, and given that the
fault has a high likelihood of being in AS0, hilarity ensues.
Sadly, the cleanest solution seems to involve another goto. Oh well, at
least it's robust...
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
drivers/gpu/drm/panfrost/panfrost_mmu.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
index e61984e26e0a..508765f80cfe 100644
--- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
+++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
@@ -413,11 +413,11 @@ addr_to_drm_mm_node(struct panfrost_device *pfdev, int as, u64 addr)
spin_lock(&pfdev->as_lock);
list_for_each_entry(mmu, &pfdev->as_lru_list, list) {
if (as == mmu->as)
- break;
+ goto found_mmu;
}
- if (as != mmu->as)
- goto out;
+ goto out;
+found_mmu:
priv = container_of(mmu, struct panfrost_file_priv, mmu);
spin_lock(&priv->mm_lock);
--
2.21.0.dirty
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dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] drm/panfrost: Don't dereference bogus MMU pointers
@ 2019-10-29 18:27 ` Rob Herring
0 siblings, 0 replies; 4+ messages in thread
From: Rob Herring @ 2019-10-29 18:27 UTC (permalink / raw)
To: Robin Murphy; +Cc: Tomeu Vizoso, Steven Price, dri-devel, linux-kernel
On Mon, Oct 28, 2019 at 3:08 PM Robin Murphy <robin.murphy@arm.com> wrote:
>
> It seems that killing an application while faults are occurring
> (particularly with a GPU in FPGA at a whopping 40MHz) can lead to
> handling a lingering page fault after all the address space contexts
> have already been freed. In this situation, the LRU list is empty so
> addr_to_drm_mm_node() ends up dereferencing the list head as if it were
> a struct panfrost_mmu entry; this leaves "mmu->as" actually pointing at
> the pfdev->alloc_mask bitmap, which is also empty, and given that the
> fault has a high likelihood of being in AS0, hilarity ensues.
>
> Sadly, the cleanest solution seems to involve another goto. Oh well, at
> least it's robust...
>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
> drivers/gpu/drm/panfrost/panfrost_mmu.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
Applied to drm-misc-fixes
Rob
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] drm/panfrost: Don't dereference bogus MMU pointers
@ 2019-10-29 18:27 ` Rob Herring
0 siblings, 0 replies; 4+ messages in thread
From: Rob Herring @ 2019-10-29 18:27 UTC (permalink / raw)
To: Robin Murphy; +Cc: linux-kernel, dri-devel, Tomeu Vizoso, Steven Price
On Mon, Oct 28, 2019 at 3:08 PM Robin Murphy <robin.murphy@arm.com> wrote:
>
> It seems that killing an application while faults are occurring
> (particularly with a GPU in FPGA at a whopping 40MHz) can lead to
> handling a lingering page fault after all the address space contexts
> have already been freed. In this situation, the LRU list is empty so
> addr_to_drm_mm_node() ends up dereferencing the list head as if it were
> a struct panfrost_mmu entry; this leaves "mmu->as" actually pointing at
> the pfdev->alloc_mask bitmap, which is also empty, and given that the
> fault has a high likelihood of being in AS0, hilarity ensues.
>
> Sadly, the cleanest solution seems to involve another goto. Oh well, at
> least it's robust...
>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
> drivers/gpu/drm/panfrost/panfrost_mmu.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
Applied to drm-misc-fixes
Rob
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2019-10-29 18:27 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2019-10-28 20:08 [PATCH] drm/panfrost: Don't dereference bogus MMU pointers Robin Murphy
2019-10-28 20:08 ` Robin Murphy
2019-10-29 18:27 ` Rob Herring
2019-10-29 18:27 ` Rob Herring
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