Messages in this thread Patch in this message | | | From | Andy Lutomirski <> | Subject | [PATCH v6 2/3] dma-api: Teach the "DMA-from-stack" check about vmapped stacks | Date | Thu, 11 Aug 2016 02:35:22 -0700 |
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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@linux-foundation.org> Cc: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Andy Lutomirski <luto@kernel.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 fcfa1939ac41..ca56d7212e8b 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> @@ -1164,11 +1165,35 @@ 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) @@ -1291,10 +1316,11 @@ 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 +1412,9 @@ 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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