From 152c862c172162d1bed85bfb9ecdf62fec9e86ae Mon Sep 17 00:00:00 2001 From: Jason Gunthorpe Date: Thu, 20 Nov 2025 14:47:42 -0400 Subject: [PATCH] iommupt: Fix unlikely flows in increase_top() Since increase_top() does it's own READ_ONCE() on top_of_table, the caller's prior READ_ONCE() could be inconsistent and the first time through the loop we may actually already have the right level if two threads are racing map. In this case new_level will be left uninitialized. Further all the exits from the loop have to either commit to the new top or free any memory allocated so the early return must be a goto err_free. Make it so the only break from the loop always sets new_level to the right value and all other exits go to err_free. Use pts.level (the pts represents the top we are stacking) within the loop instead of new_level. Fixes: dcd6a011a8d5 ("iommupt: Add map_pages op") Reported-by: Dan Carpenter Closes: https://lore.kernel.org/r/aRwgNW9PiW2j-Qwo@stanley.mountain Signed-off-by: Jason Gunthorpe Reviewed-by: Alejandro Jimenez Reviewed-by: Vasant Hegde Reviewed-by: Kevin Tian Signed-off-by: Joerg Roedel --- drivers/iommu/generic_pt/iommu_pt.h | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/drivers/iommu/generic_pt/iommu_pt.h b/drivers/iommu/generic_pt/iommu_pt.h index 0e046fe0eea34..032d04ec7b568 100644 --- a/drivers/iommu/generic_pt/iommu_pt.h +++ b/drivers/iommu/generic_pt/iommu_pt.h @@ -683,8 +683,11 @@ static int increase_top(struct pt_iommu *iommu_table, struct pt_range *range, top_range.va = range->va; top_range.last_va = range->last_va; - if (!pt_check_range(&top_range) && map->leaf_level <= pts.level) + if (!pt_check_range(&top_range) && + map->leaf_level <= pts.level) { + new_level = pts.level; break; + } pts.level++; if (pts.level > PT_MAX_TOP_LEVEL || @@ -693,17 +696,18 @@ static int increase_top(struct pt_iommu *iommu_table, struct pt_range *range, goto err_free; } - new_level = pts.level; table_mem = table_alloc_top(common, _pt_top_set(NULL, pts.level), map->attrs.gfp, ALLOC_DEFER_COHERENT_FLUSH); - if (IS_ERR(table_mem)) - return PTR_ERR(table_mem); + if (IS_ERR(table_mem)) { + ret = PTR_ERR(table_mem); + goto err_free; + } iommu_pages_list_add(&free_list, table_mem); /* The new table links to the lower table always at index 0 */ top_range.va = 0; - top_range.top_level = new_level; + top_range.top_level = pts.level; pts.table_lower = pts.table; pts.table = table_mem; pt_load_single_entry(&pts); @@ -735,7 +739,8 @@ static int increase_top(struct pt_iommu *iommu_table, struct pt_range *range, */ domain_lock = iommu_table->driver_ops->get_top_lock(iommu_table); spin_lock_irqsave(domain_lock, flags); - if (common->top_of_table != top_of_table) { + if (common->top_of_table != top_of_table || + top_of_table == new_top_of_table) { spin_unlock_irqrestore(domain_lock, flags); ret = -EAGAIN; goto err_free; -- 2.47.3