2 files changed, 43 insertions, 8 deletions

diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index fcfa1939ac41..06f02f6aecd2 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 +1165,32 @@ 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)
 {
-        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 +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));
                 }
 
diff --git a/lib/syscall.c b/lib/syscall.c
index e30e03932480..63239e097b13 100644
--- a/lib/syscall.c
+++ b/lib/syscall.c
@@ -7,9 +7,19 @@ static int collect_syscall(struct task_struct *target, long *callno,
                            unsigned long args[6], unsigned int maxargs,
                            unsigned long *sp, unsigned long *pc)
 {
-        struct pt_regs *regs = task_pt_regs(target);
-        if (unlikely(!regs))
+        struct pt_regs *regs;
+
+        if (!try_get_task_stack(target)) {
+                /* Task has no stack, so the task isn't in a syscall. */
+                *callno = -1;
+                return 0;
+        }
+
+        regs = task_pt_regs(target);
+        if (unlikely(!regs)) {
+                put_task_stack(target);
                 return -EAGAIN;
+        }
 
         *sp = user_stack_pointer(regs);
         *pc = instruction_pointer(regs);
@@ -18,6 +28,7 @@ static int collect_syscall(struct task_struct *target, long *callno,
         if (*callno != -1L && maxargs > 0)
                 syscall_get_arguments(target, regs, 0, maxargs, args);
 
+        put_task_stack(target);
         return 0;
 }