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Date: Sun, 26 Jun 2016 14:55:30 -0700
From: Andy Lutomirski <luto@...nel.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
linux-arch@...r.kernel.org,
Borislav Petkov <bp@...en8.de>,
Nadav Amit <nadav.amit@...il.com>,
Kees Cook <keescook@...omium.org>,
Brian Gerst <brgerst@...il.com>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Jann Horn <jann@...jh.net>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Andy Lutomirski <luto@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Arnd Bergmann <arnd@...db.de>
Subject: [PATCH v4 08/29] dma-api: Teach the "DMA-from-stack" check about vmapped stacks
If we're using CONFIG_VMAP_STACK and we manage to point an sg entry
at the stack, then either the sg page will be in highmem or sg_virt
will return the direct-map alias. In neither case will the existing
check_for_stack() implementation realize that it's a stack page.
Fix it by explicitly checking for stack pages.
This has no effect by itself. It's broken out for ease of review.
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
lib/dma-debug.c | 39 +++++++++++++++++++++++++++++++++------
1 file changed, 33 insertions(+), 6 deletions(-)
diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index 51a76af25c66..5b2e63cba90e 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -22,6 +22,7 @@
#include <linux/stacktrace.h>
#include <linux/dma-debug.h>
#include <linux/spinlock.h>
+#include <linux/vmalloc.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/export.h>
@@ -1162,11 +1163,35 @@ static void check_unmap(struct dma_debug_entry *ref)
put_hash_bucket(bucket, &flags);
}
-static void check_for_stack(struct device *dev, void *addr)
+static void check_for_stack(struct device *dev,
+ struct page *page, size_t offset)
{
- if (object_is_on_stack(addr))
- err_printk(dev, NULL, "DMA-API: device driver maps memory from "
- "stack [addr=%p]\n", addr);
+ void *addr;
+ struct vm_struct *stack_vm_area = task_stack_vm_area(current);
+
+ if (!stack_vm_area) {
+ /* Stack is direct-mapped. */
+ if (PageHighMem(page))
+ return;
+ addr = page_address(page) + offset;
+ if (object_is_on_stack(addr))
+ err_printk(dev, NULL, "DMA-API: device driver maps memory from stack [addr=%p]\n",
+ addr);
+ } else {
+ /* Stack is vmalloced. */
+ int i;
+
+ for (i = 0; i < stack_vm_area->nr_pages; i++) {
+ if (page != stack_vm_area->pages[i])
+ continue;
+
+ addr = (u8 *)current->stack + i * PAGE_SIZE +
+ offset;
+ err_printk(dev, NULL, "DMA-API: device driver maps memory from stack [probable addr=%p]\n",
+ addr);
+ break;
+ }
+ }
}
static inline bool overlap(void *addr, unsigned long len, void *start, void *end)
@@ -1289,10 +1314,11 @@ void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
if (map_single)
entry->type = dma_debug_single;
+ check_for_stack(dev, page, offset);
+
if (!PageHighMem(page)) {
void *addr = page_address(page) + offset;
- check_for_stack(dev, addr);
check_for_illegal_area(dev, addr, size);
}
@@ -1384,8 +1410,9 @@ void debug_dma_map_sg(struct device *dev, struct scatterlist *sg,
entry->sg_call_ents = nents;
entry->sg_mapped_ents = mapped_ents;
+ check_for_stack(dev, sg_page(s), s->offset);
+
if (!PageHighMem(sg_page(s))) {
- check_for_stack(dev, sg_virt(s));
check_for_illegal_area(dev, sg_virt(s), sg_dma_len(s));
}
--
2.7.4
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