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Date: Mon, 19 Jul 2021 13:30:51 +0100
From: Will Deacon <will@...nel.org>
To: iommu@...ts.linux-foundation.org
Cc: linux-kernel@...r.kernel.org, Will Deacon <will@...nel.org>,
Guenter Roeck <linux@...ck-us.net>,
Claire Chang <tientzu@...omium.org>,
Christoph Hellwig <hch@....de>,
Robin Murphy <robin.murphy@....com>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH 2/5] swiotlb: Point io_default_tlb_mem at static allocation
Since commit 69031f500865 ("swiotlb: Set dev->dma_io_tlb_mem to the
swiotlb pool used"), 'struct device' may hold a copy of the global
'io_default_tlb_mem' pointer if the device is using swiotlb for DMA. A
subsequent call to swiotlb_exit() will therefore leave dangling pointers
behind in these device structures, resulting in KASAN splats such as:
| BUG: KASAN: use-after-free in __iommu_dma_unmap_swiotlb+0x64/0xb0
| Read of size 8 at addr ffff8881d7830000 by task swapper/0/0
|
| CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.12.0-rc3-debug #1
| Hardware name: HP HP Desktop M01-F1xxx/87D6, BIOS F.12 12/17/2020
| Call Trace:
| <IRQ>
| dump_stack+0x9c/0xcf
| print_address_description.constprop.0+0x18/0x130
| kasan_report.cold+0x7f/0x111
| __iommu_dma_unmap_swiotlb+0x64/0xb0
| nvme_pci_complete_rq+0x73/0x130
| blk_complete_reqs+0x6f/0x80
| __do_softirq+0xfc/0x3be
Point 'io_default_tlb_mem' at a static structure, so that the per-device
pointers remain valid after swiotlb_exit() has been invoked. The 'slots'
array is still allocated dynamically and referenced via a pointer rather
than a flexible array member.
Cc: Claire Chang <tientzu@...omium.org>
Cc: Christoph Hellwig <hch@....de>
Cc: Robin Murphy <robin.murphy@....com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Fixes: 69031f500865 ("swiotlb: Set dev->dma_io_tlb_mem to the swiotlb pool used")
Reported-by: Nathan Chancellor <nathan@...nel.org>
Tested-by: Nathan Chancellor <nathan@...nel.org>
Signed-off-by: Will Deacon <will@...nel.org>
---
include/linux/swiotlb.h | 2 +-
kernel/dma/swiotlb.c | 34 +++++++++++++++++++++-------------
2 files changed, 22 insertions(+), 14 deletions(-)
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 39284ff2a6cd..d3b617c19045 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -103,7 +103,7 @@ struct io_tlb_mem {
phys_addr_t orig_addr;
size_t alloc_size;
unsigned int list;
- } slots[];
+ } *slots;
};
extern struct io_tlb_mem *io_tlb_default_mem;
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index f1a9ae7fad8f..992d73cdc944 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -71,6 +71,7 @@
enum swiotlb_force swiotlb_force;
struct io_tlb_mem *io_tlb_default_mem;
+static struct io_tlb_mem _io_tlb_default_mem;
/*
* Max segment that we can provide which (if pages are contingous) will
@@ -201,7 +202,7 @@ static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t start,
int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
{
- struct io_tlb_mem *mem;
+ struct io_tlb_mem *mem = &_io_tlb_default_mem;
size_t alloc_size;
if (swiotlb_force == SWIOTLB_NO_FORCE)
@@ -211,9 +212,9 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
if (WARN_ON_ONCE(io_tlb_default_mem))
return -ENOMEM;
- alloc_size = PAGE_ALIGN(struct_size(mem, slots, nslabs));
- mem = memblock_alloc(alloc_size, PAGE_SIZE);
- if (!mem)
+ alloc_size = PAGE_ALIGN(array_size(sizeof(*mem->slots), nslabs));
+ mem->slots = memblock_alloc(alloc_size, PAGE_SIZE);
+ if (!mem->slots)
panic("%s: Failed to allocate %zu bytes align=0x%lx\n",
__func__, alloc_size, PAGE_SIZE);
@@ -304,7 +305,7 @@ swiotlb_late_init_with_default_size(size_t default_size)
int
swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
{
- struct io_tlb_mem *mem;
+ struct io_tlb_mem *mem = &_io_tlb_default_mem;
unsigned long bytes = nslabs << IO_TLB_SHIFT;
if (swiotlb_force == SWIOTLB_NO_FORCE)
@@ -314,12 +315,11 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
if (WARN_ON_ONCE(io_tlb_default_mem))
return -ENOMEM;
- mem = (void *)__get_free_pages(GFP_KERNEL,
- get_order(struct_size(mem, slots, nslabs)));
- if (!mem)
+ mem->slots = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
+ get_order(array_size(sizeof(*mem->slots), nslabs)));
+ if (!mem->slots)
return -ENOMEM;
- memset(mem, 0, sizeof(*mem));
set_memory_decrypted((unsigned long)tlb, bytes >> PAGE_SHIFT);
swiotlb_init_io_tlb_mem(mem, virt_to_phys(tlb), nslabs, true);
@@ -337,12 +337,13 @@ void __init swiotlb_exit(void)
if (!mem)
return;
- size = struct_size(mem, slots, mem->nslabs);
+ size = array_size(sizeof(*mem->slots), mem->nslabs);
if (mem->late_alloc)
- free_pages((unsigned long)mem, get_order(size));
+ free_pages((unsigned long)mem->slots, get_order(size));
else
- memblock_free_late(__pa(mem), PAGE_ALIGN(size));
+ memblock_free_late(__pa(mem->slots), PAGE_ALIGN(size));
io_tlb_default_mem = NULL;
+ memset(mem, 0, sizeof(*mem));
}
/*
@@ -783,10 +784,17 @@ static int rmem_swiotlb_device_init(struct reserved_mem *rmem,
* to it.
*/
if (!mem) {
- mem = kzalloc(struct_size(mem, slots, nslabs), GFP_KERNEL);
+ mem = kzalloc(sizeof(*mem), GFP_KERNEL);
if (!mem)
return -ENOMEM;
+ mem->slots = kzalloc(array_size(sizeof(*mem->slots), nslabs),
+ GFP_KERNEL);
+ if (!mem->slots) {
+ kfree(mem);
+ return -ENOMEM;
+ }
+
set_memory_decrypted((unsigned long)phys_to_virt(rmem->base),
rmem->size >> PAGE_SHIFT);
swiotlb_init_io_tlb_mem(mem, rmem->base, nslabs, false);
--
2.32.0.402.g57bb445576-goog
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