Re: [PATCH v6 06/17] iommu/arm-smmu-v3: Don't rb_erase() a never-inserted stream node
From: Mostafa Saleh <smostafa@google.com>
Date: 2026-09-24 08:21:04
Also in:
linux-acpi, linux-cxl, linux-iommu, linux-pci, lkml
On Wed, Sep 23, 2026 at 01:11:25PM -0700, Nicolin Chen wrote:
arm_smmu_insert_master() skips inserting a stream whose StreamID duplicates
one the same master already owns (bridged PCI devices can present duplicate
IDs), leaving that master->streams[i].node zeroed and unlinked from the
smmu->streams rb-tree.
Both the insert error-rollback loop and arm_smmu_remove_master() then call
rb_erase() on every master->streams[i].node unconditionally. rb_erase() on
a zeroed node sees a NULL parent, treats the node as the tree root and sets
root->rb_node = NULL, silently emptying the whole SID tree and breaking SID
lookups (and DMA) for every other master on the SMMU.
Mark each node with RB_CLEAR_NODE() after sort_nonatomic() reorders the
array, since sorting relocates the entries and would leave the earlier
self-referential RB_CLEAR_NODE() pointer stale. An un-inserted node then
stays RB_EMPTY_NODE() and is skipped in both erase loops; inserted nodes
are linked by rb_find_add() and erased as before.
Fixes: b00d24997a11 ("iommu/arm-smmu-v3: Fix iommu_device_probe bug due to duplicated stream ids")
Assisted-by: LLM
Signed-off-by: Nicolin Chen <redacted>Reviewed-by: Mostafa Saleh <smostafa@google.com> Thanks, Mostafa
quoted hunk ↗ jump to hunk
--- drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-)diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c index 5732f3ba0122d..082da3dc09e56 100644 --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c@@ -4122,6 +4122,13 @@ static int arm_smmu_insert_master(struct arm_smmu_device *smmu, sizeof(master->streams[0]), arm_smmu_stream_id_cmp, NULL); + /* + * Clear after sorting: RB_CLEAR_NODE() records the node's own address, + * which sort_nonatomic() invalidates by relocating the entries. + */ + for (i = 0; i < fwspec->num_ids; i++) + RB_CLEAR_NODE(&master->streams[i].node); + mutex_lock(&smmu->streams_mutex); for (i = 0; i < fwspec->num_ids; i++) { struct arm_smmu_stream *new_stream = &master->streams[i];@@ -4154,7 +4161,9 @@ static int arm_smmu_insert_master(struct arm_smmu_device *smmu, if (ret) { for (i--; i >= 0; i--) - rb_erase(&master->streams[i].node, &smmu->streams); + if (!RB_EMPTY_NODE(&master->streams[i].node)) + rb_erase(&master->streams[i].node, + &smmu->streams); kfree(master->streams); kfree(master->build_invs); }@@ -4174,7 +4183,8 @@ static void arm_smmu_remove_master(struct arm_smmu_master *master) mutex_lock(&smmu->streams_mutex); for (i = 0; i < fwspec->num_ids; i++) - rb_erase(&master->streams[i].node, &smmu->streams); + if (!RB_EMPTY_NODE(&master->streams[i].node)) + rb_erase(&master->streams[i].node, &smmu->streams); mutex_unlock(&smmu->streams_mutex); kfree(master->streams);-- 2.43.0