iommu/amd: Check PM_LEVEL_SIZE() condition in locked section

The increase_address_space() function has to check the PM_LEVEL_SIZE()
condition again under the domain->lock to avoid a false trigger of the
WARN_ON_ONCE() and to avoid that the address space is increase more
often than necessary.

Reported-by: Qian Cai <cai@lca.pw>
Fixes: 2059792d54e3 ("iommu/amd: Fix race in increase_address_space()")
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index bcd89ea50a8bc784da919122538cd47cb2e3b4ad..dd555078258c437c375902538ecc2f9040efd7cc 100644 (file)
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -1464,6 +1464,7 @@ static void free_pagetable(struct protection_domain *domain)
  * to 64 bits.
  */
 static bool increase_address_space(struct protection_domain *domain,
+                                  unsigned long address,
                                   gfp_t gfp)
 {
        unsigned long flags;
@@ -1472,8 +1473,8 @@ static bool increase_address_space(struct protection_domain *domain,
 
        spin_lock_irqsave(&domain->lock, flags);
 
-       if (WARN_ON_ONCE(domain->mode == PAGE_MODE_6_LEVEL))
-               /* address space already 64 bit large */
+       if (address <= PM_LEVEL_SIZE(domain->mode) ||
+           WARN_ON_ONCE(domain->mode == PAGE_MODE_6_LEVEL))
                goto out;
 
        pte = (void *)get_zeroed_page(gfp);
@@ -1506,7 +1507,7 @@ static u64 *alloc_pte(struct protection_domain *domain,
        BUG_ON(!is_power_of_2(page_size));
 
        while (address > PM_LEVEL_SIZE(domain->mode))
-               *updated = increase_address_space(domain, gfp) || *updated;
+               *updated = increase_address_space(domain, address, gfp) || *updated;
 
        level   = domain->mode - 1;
        pte     = &domain->pt_root[PM_LEVEL_INDEX(level, address)];