linux-kernel - [PATCH v2] drm/panthor: Lock XArray when getting entries for the VM

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Message-ID: <20241106185806.389089-1-liviu.dudau@arm.com>
Date: Wed,  6 Nov 2024 18:58:06 +0000
From: Liviu Dudau <liviu.dudau@....com>
To: Boris Brezillon <boris.brezillon@...labora.com>
Cc: Liviu Dudau <liviu.dudau@....com>,
	Steven Price <steven.price@....com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	Jann Horn <jannh@...gle.com>
Subject: [PATCH v2] drm/panthor: Lock XArray when getting entries for the VM

Similar to cac075706f29 ("drm/panthor: Fix race when converting
group handle to group object") we need to use the XArray's internal
locking when retrieving a vm pointer from there.

v2: Removed part of the patch that was trying to protect fetching
the heap pointer from XArray, as that operation is protected by
the @pool->lock.

Fixes: 647810ec2476 ("drm/panthor: Add the MMU/VM logical block")
Reported-by: Jann Horn <jannh@...gle.com>
Cc: Boris Brezillon <boris.brezillon@...labora.com>
Cc: Steven Price <steven.price@....com>
Signed-off-by: Liviu Dudau <liviu.dudau@....com>
---
 drivers/gpu/drm/panthor/panthor_mmu.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
index 8ca85526491e6..46b84a557d9cc 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -1580,7 +1580,9 @@ panthor_vm_pool_get_vm(struct panthor_vm_pool *pool, u32 handle)
 {
 	struct panthor_vm *vm;
 
+	xa_lock(&pool->xa);
 	vm = panthor_vm_get(xa_load(&pool->xa, handle));
+	xa_unlock(&pool->xa);
 
 	return vm;
 }
-- 
2.47.0