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dma-direct: don't over-decrypt memory

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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: c10f07aa27 ("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>
This commit is contained in:
Robin Murphy 2022-05-20 18:10:13 +01:00 committed by Greg Kroah-Hartman
parent aa9a001efa
commit 73bc8a5e8e
1 changed files with 6 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
kernel/dma/direct.c
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@ -188,7 +188,7 @@ void *dma_direct_alloc(struct device *dev, size_t size,
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 *dev, size_t size,
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 @@ void *dma_direct_alloc(struct device *dev, size_t size,
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 @@ void *dma_direct_alloc(struct device *dev, size_t size,
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, size_t size,
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(struct device *dev, size_t size,
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 *dev, size_t size,
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 *dev, size_t size,
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);
}