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iommu: debug-pagealloc: Check mapped/unmapped kernel memory

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Now, as the page_ext holds count of IOMMU mappings, we can use it to
assert that any page allocated/freed is indeed not in the IOMMU.

The sanitizer doesn’t protect against mapping/unmapping during this
period. However, that’s less harmful as the page is not used by the
kernel.

Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Reviewed-by: Pranjal Shrivastava <praan@google.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
This commit is contained in:
Mostafa Saleh
2026-01-09 17:18:05 +00:00
committed by Joerg Roedel
parent 7e84593795
commit a8258ffed2
3 changed files with 42 additions and 0 deletions
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23
drivers/iommu/iommu-debug-pagealloc.c
View File

@@ -9,6 +9,7 @@
#include <linux/iommu-debug-pagealloc.h>
#include <linux/kernel.h>
#include <linux/page_ext.h>
#include <linux/page_owner.h>
#include "iommu-priv.h"
@@ -73,6 +74,28 @@ static size_t iommu_debug_page_size(struct iommu_domain *domain)
return 1UL << __ffs(domain->pgsize_bitmap);
}
static bool iommu_debug_page_count(const struct page *page)
{
unsigned int ref;
struct page_ext *page_ext = page_ext_get(page);
struct iommu_debug_metadata *d = get_iommu_data(page_ext);
ref = atomic_read(&d->ref);
page_ext_put(page_ext);
return ref != 0;
}
void __iommu_debug_check_unmapped(const struct page *page, int numpages)
{
while (numpages--) {
if (WARN_ON(iommu_debug_page_count(page))) {
pr_warn("iommu: Detected page leak!\n");
dump_page_owner(page);
}
page++;
}
}
void __iommu_debug_map(struct iommu_domain *domain, phys_addr_t phys, size_t size)
{
size_t off, end;

14
include/linux/iommu-debug-pagealloc.h
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@@ -13,6 +13,20 @@ DECLARE_STATIC_KEY_FALSE(iommu_debug_initialized);
extern struct page_ext_operations page_iommu_debug_ops;
void __iommu_debug_check_unmapped(const struct page *page, int numpages);
static inline void iommu_debug_check_unmapped(const struct page *page, int numpages)
{
if (static_branch_unlikely(&iommu_debug_initialized))
__iommu_debug_check_unmapped(page, numpages);
}
#else
static inline void iommu_debug_check_unmapped(const struct page *page,
int numpages)
{
}
#endif /* CONFIG_IOMMU_DEBUG_PAGEALLOC */
#endif /* __LINUX_IOMMU_DEBUG_PAGEALLOC_H */

5
include/linux/mm.h
View File

@@ -36,6 +36,7 @@
#include <linux/rcuwait.h>
#include <linux/bitmap.h>
#include <linux/bitops.h>
#include <linux/iommu-debug-pagealloc.h>
struct mempolicy;
struct anon_vma;
@@ -4133,12 +4134,16 @@ extern void __kernel_map_pages(struct page *page, int numpages, int enable);
#ifdef CONFIG_DEBUG_PAGEALLOC
static inline void debug_pagealloc_map_pages(struct page *page, int numpages)
{
iommu_debug_check_unmapped(page, numpages);
if (debug_pagealloc_enabled_static())
__kernel_map_pages(page, numpages, 1);
}
static inline void debug_pagealloc_unmap_pages(struct page *page, int numpages)
{
iommu_debug_check_unmapped(page, numpages);
if (debug_pagealloc_enabled_static())
__kernel_map_pages(page, numpages, 0);
}