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Subject[PATCH stable 4.9] iommu/amd: Fix sleeping in atomic in increase_address_space()
Date
commit 140456f994195b568ecd7fc2287a34eadffef3ca upstream.

increase_address_space() calls get_zeroed_page(gfp) under spin_lock with
disabled interrupts. gfp flags passed to increase_address_space() may allow
sleeping, so it comes to this:

BUG: sleeping function called from invalid context at mm/page_alloc.c:4342
in_atomic(): 1, irqs_disabled(): 1, pid: 21555, name: epdcbbf1qnhbsd8

Call Trace:
dump_stack+0x66/0x8b
___might_sleep+0xec/0x110
__alloc_pages_nodemask+0x104/0x300
get_zeroed_page+0x15/0x40
iommu_map_page+0xdd/0x3e0
amd_iommu_map+0x50/0x70
iommu_map+0x106/0x220
vfio_iommu_type1_ioctl+0x76e/0x950 [vfio_iommu_type1]
do_vfs_ioctl+0xa3/0x6f0
ksys_ioctl+0x66/0x70
__x64_sys_ioctl+0x16/0x20
do_syscall_64+0x4e/0x100
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fix this by moving get_zeroed_page() out of spin_lock/unlock section.

Fixes: 754265bcab ("iommu/amd: Fix race in increase_address_space()")
Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210217143004.19165-1-arbn@yandex-team.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com>
---
drivers/iommu/amd_iommu.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index f4a15d9f2bbb2..8377bd388d673 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -1331,24 +1331,26 @@ static void increase_address_space(struct protection_domain *domain,
unsigned long flags;
u64 *pte;

+ pte = (void *)get_zeroed_page(gfp);
+ if (!pte)
+ goto out;
+
spin_lock_irqsave(&domain->lock, flags);

if (WARN_ON_ONCE(domain->mode == PAGE_MODE_6_LEVEL))
/* address space already 64 bit large */
goto out;

- pte = (void *)get_zeroed_page(gfp);
- if (!pte)
- goto out;
-
*pte = PM_LEVEL_PDE(domain->mode,
virt_to_phys(domain->pt_root));
domain->pt_root = pte;
domain->mode += 1;
domain->updated = true;
+ pte = NULL;

out:
spin_unlock_irqrestore(&domain->lock, flags);
+ free_page((unsigned long)pte);

return;
}
--
2.26.2
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