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Commit b4a0f533 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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dma-api: Teach the "DMA-from-stack" check about vmapped stacks 



If we're using CONFIG_VMAP_STACK=y 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.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/448460622731312298bf19dcbacb1606e75de7a9.1470907718.git.luto@kernel.org


[ Minor edits. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent ba14a194

lib/dma-debug.c

+30 −6
Original line number Diff line number Diff line
@@ -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>
@@ -1164,11 +1165,32 @@ 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)

{

	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);

			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)
@@ -1291,10 +1313,11 @@ 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);

	}
@@ -1386,8 +1409,9 @@ 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));

		}