[PATCH 5.10 78/84] dma-direct: dont over-decrypt memory

Greg Kroah-Hartman
2022-06-20T13:17:47Z

From: Robin Murphy <robin.murphy@arm.com>

commit 4a37f3dd9a83186cb88d44808ab35b78375082c9 upstream.

The original x86 sev_alloc() only called set_memory_decrypted() on
memory returned by alloc_pages_node(), so the page order calculation
fell out of that logic. However, the common dma-direct code has several
potential allocators, not all of which are guaranteed to round up the
underlying allocation to a power-of-two size, so carrying over that
calculation for the encryption/decryption size was a mistake. Fix it by
rounding to a *number* of pages, rather than an order.

Until recently there was an even worse interaction with DMA_DIRECT_REMAP
where we could have ended up decrypting part of the next adjacent
vmalloc area, only averted by no architecture actually supporting both
configs at once. Don't ask how I found that one out...

Fixes: c10f07aa27da ("dma/direct: Handle force decryption for DMA coherent buffers in common code")
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: David Rientjes <rientjes@google.com>
[ backport the functional change without all the prior refactoring ]
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/dma/direct.c | 16 ++++++----------
1 file changed, 6 insertions(+), 10 deletions(-)

--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -188,7 +188,7 @@ void *dma_direct_alloc(struct device *de
goto out_free_pages;
if (force_dma_unencrypted(dev)) {
err = set_memory_decrypted((unsigned long)ret,
- 1 << get_order(size));
+ PFN_UP(size));
if (err)
goto out_free_pages;
}
@@ -210,7 +210,7 @@ void *dma_direct_alloc(struct device *de
ret = page_address(page);
if (force_dma_unencrypted(dev)) {
err = set_memory_decrypted((unsigned long)ret,
- 1 << get_order(size));
+ PFN_UP(size));
if (err)
goto out_free_pages;
}
@@ -231,7 +231,7 @@ done:
out_encrypt_pages:
if (force_dma_unencrypted(dev)) {
err = set_memory_encrypted((unsigned long)page_address(page),
- 1 << get_order(size));
+ PFN_UP(size));
/* If memory cannot be re-encrypted, it must be leaked */
if (err)
return NULL;
@@ -244,8 +244,6 @@ out_free_pages:
void dma_direct_free(struct device *dev, size_t size,
void *cpu_addr, dma_addr_t dma_addr, unsigned long attrs)
{
- unsigned int page_order = get_order(size);
-
if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) &&
!force_dma_unencrypted(dev)) {
/* cpu_addr is a struct page cookie, not a kernel address */
@@ -266,7 +264,7 @@ void dma_direct_free(struct device *dev,
return;

if (force_dma_unencrypted(dev))
- set_memory_encrypted((unsigned long)cpu_addr, 1 << page_order);
+ set_memory_encrypted((unsigned long)cpu_addr, PFN_UP(size));

if (IS_ENABLED(CONFIG_DMA_REMAP) && is_vmalloc_addr(cpu_addr))
vunmap(cpu_addr);
@@ -302,8 +300,7 @@ struct page *dma_direct_alloc_pages(stru

ret = page_address(page);
if (force_dma_unencrypted(dev)) {
- if (set_memory_decrypted((unsigned long)ret,
- 1 << get_order(size)))
+ if (set_memory_decrypted((unsigned long)ret, PFN_UP(size)))
goto out_free_pages;
}
memset(ret, 0, size);
@@ -318,7 +315,6 @@ void dma_direct_free_pages(struct device
struct page *page, dma_addr_t dma_addr,
enum dma_data_direction dir)
{
- unsigned int page_order = get_order(size);
void *vaddr = page_address(page);

/* If cpu_addr is not from an atomic pool, dma_free_from_pool() fails */
@@ -327,7 +323,7 @@ void dma_direct_free_pages(struct device
return;

if (force_dma_unencrypted(dev))
- set_memory_encrypted((unsigned long)vaddr, 1 << page_order);
+ set_memory_encrypted((unsigned long)vaddr, PFN_UP(size));

dma_free_contiguous(dev, page, size);
}