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Moore" > > gfx_v9_0_ring_emit_fence_kiq() contains a BUG_ON() that fires when > the AMDGPU_FENCE_FLAG_64BIT flag is passed. The KIQ (Kernel > Interface Queue) ring only allocates 32-bit writeback buffer > addresses for fence sequence numbers. A 64-bit fence write would > overflow the allocated writeback slot, potentially corrupting > adjacent kernel memory. > > Replace BUG_ON() with WARN_ON_ONCE() and mask off the unsupported > flag. This prevents the kernel panic while still logging the > unexpected condition and falling back to a safe 32-bit fence write. > > This is separated from the main gfx9 BUG_ON conversion patch > because it addresses a different security concern (potential buffer > overflow in kernel-managed writeback memory) rather than the address > alignment assertions in the ring emission paths. > > Found by a custom amdgpu DRM ioctl fuzzer. > > Fixes: b1023571479020e9 ("drm/amdgpu: implement GFX 9.0 support (v2)") > Signed-off-by: John B. Moore > Cc: stable@vger.kernel.org > --- > drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c > index 47e81c33d..fb2a0f1af 100644 > --- a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c > +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c > @@ -5679,7 +5679,8 @@ static void gfx_v9_0_ring_emit_fence_kiq(struct amdgpu_ring *ring, u64 addr, > struct amdgpu_device *adev = ring->adev; > > /* we only allocate 32bit for each seq wb address */ > - BUG_ON(flags & AMDGPU_FENCE_FLAG_64BIT); > + if (WARN_ON_ONCE(flags & AMDGPU_FENCE_FLAG_64BIT)) Please use only WARN_ON() and not WARN_ON_ONCE(). > + flags &= ~AMDGPU_FENCE_FLAG_64BIT; I don't think we should mask the flag here. Regards, Christian. > > /* write fence seq to the "addr" */ > amdgpu_ring_write(ring, PACKET3(PACKET3_WRITE_DATA, 3));