Re: [PATCH] iommu/arm-smmu-v3: Skip unlinked duplicate stream nodes on removal

[Nicolin Chen]

On Mon, Sep 21, 2026 at 08:17:27PM +0800, zhoumin wrote:
> A master's firmware stream ID list can contain duplicates, for example
> for PCI devices behind an aliasing bridge. arm_smmu_insert_master()
> accepts these IDs when the existing stream belongs to the same master,
> but does not link the duplicate stream's rb_node into the SID tree.
> 
> Both arm_smmu_remove_master() and the insertion error path nevertheless
> call rb_erase() for every stream in their respective ranges. Erasing a
> zero-initialized, unlinked node can clear the tree root, losing SID to
> master mappings for other devices sharing the SMMU and leaving the tree
> inconsistent for subsequent operations.
> 
> Mark skipped duplicate nodes with RB_CLEAR_NODE() and skip them in both
> removal paths. Set the marker after sorting the stream array, since it
> contains the node's own address. Keep the stream array and num_streams
> unchanged to preserve existing STE, invalidation and single-stream
> feature checks.
> 
> Fixes: b00d24997a11 ("iommu/arm-smmu-v3: Fix iommu_device_probe bug due to duplicated stream ids") 

I submitted a similar fix a while ago:
https://lore.kernel.org/linux-iommu/9136477b9c737a50cecc38f2ee6704a01510169a.1783044582.git.nicolinc@xxxxxxxxxx/

I wonder if you really hit the issue or it's just a Sashiko finding?

Nicolin