Messages in this thread | | | Date | Tue, 5 Apr 2022 13:00:42 -0400 | Subject | Re: [PATCH] drm/amdkfd: Fix potential NULL pointer dereference | From | Felix Kuehling <> |
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Am 2022-04-04 um 18:21 schrieb Grigory Vasilyev: > In the amdgpu_amdkfd_get_xgmi_bandwidth_mbytes function, > the peer_adev pointer can be NULL and is passed to amdgpu_xgmi_get_num_links. > > In amdgpu_xgmi_get_num_links, peer_adev pointer is dereferenced > without any checks: peer_adev->gmc.xgmi.node_id .
What's worse, peer_adev is uninitialized with an undefined value if src is NULL. So that code was definitely bogus.
However, I think your patch will result in incorrect results. Currently amdgpu_amdkfd_get_xgmi_bandwidth is always called with is_min=true if src==NULL, and with is_min=false if src!=NULL. The intention is, that we assume a single XGMI link in the case that src==NULL. That means the is_min parameter is redundant. What we should do instead is, assume that num_links==1 if src==NULL, and drop the is_min parameter.
That would keep things working the way they do now, and prevent potential problems in the future.
Regards, Felix
> > Signed-off-by: Grigory Vasilyev <h0tc0d3@gmail.com> > --- > drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c > index be1a55f8b8c5..1a1006b18016 100644 > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c > @@ -541,11 +541,10 @@ int amdgpu_amdkfd_get_xgmi_bandwidth_mbytes(struct amdgpu_device *dst, > struct amdgpu_device *adev = dst, *peer_adev; > int num_links; > > - if (adev->asic_type != CHIP_ALDEBARAN) > + if (!src || adev->asic_type != CHIP_ALDEBARAN) > return 0; > > - if (src) > - peer_adev = src; > + peer_adev = src; > > /* num links returns 0 for indirect peers since indirect route is unknown. */ > num_links = is_min ? 1 : amdgpu_xgmi_get_num_links(adev, peer_adev);
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