| Message ID | 20191018093830.GA26328@suse.de (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | iommu/amd: Check PM_LEVEL_SIZE() condition in locked section | expand |
On Fri Oct 18 19, Joerg Roedel wrote: >On Thu, Oct 17, 2019 at 07:36:51AM -0400, Qian Cai wrote: >> >> >> > On Oct 16, 2019, at 6:59 PM, Jerry Snitselaar <jsnitsel@redhat.com> wrote: >> > >> > I guess the mode level 6 check is really for other potential callers >> > increase_address_space, none exist at the moment, and the condition >> > of the while loop in alloc_pte should fail if the mode level is 6. >> >> Because there is no locking around iommu_map_page(), if there are >> several concurrent callers of it for the same domain, could it be that >> it silently corrupt data due to invalid access? > >No, that can't happen because increase_address_space locks the domain >before actually doing anything. So the address space can't grow above >domain->mode == 6. But what can happen is that the WARN_ON_ONCE triggers >in there and that the address space is increased multiple times when >only one increase would be sufficient. > >To fix this we just need to check the PM_LEVEL_SIZE() condition again >when we hold the lock: > >From e930e792a998e89dfd4feef15fbbf289c45124dc Mon Sep 17 00:00:00 2001 >From: Joerg Roedel <jroedel@suse.de> >Date: Fri, 18 Oct 2019 11:34:22 +0200 >Subject: [PATCH] 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: 754265bcab78 ("iommu/amd: Fix race in increase_address_space()") >Signed-off-by: Joerg Roedel <jroedel@suse.de> >--- > drivers/iommu/amd_iommu.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > >diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c >index 2369b8af81f3..a0639e511ffe 100644 >--- a/drivers/iommu/amd_iommu.c >+++ b/drivers/iommu/amd_iommu.c >@@ -1463,6 +1463,7 @@ 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; >@@ -1471,8 +1472,8 @@ 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); >@@ -1505,7 +1506,7 @@ 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)]; >-- >2.16.4 > Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c index 2369b8af81f3..a0639e511ffe 100644 --- a/drivers/iommu/amd_iommu.c +++ b/drivers/iommu/amd_iommu.c @@ -1463,6 +1463,7 @@ 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; @@ -1471,8 +1472,8 @@ 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); @@ -1505,7 +1506,7 @@ 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)];