path: root/mm
diff options
authorAndrey Ryabinin <a.ryabinin@samsung.com>2015-03-12 16:26:11 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-03-12 18:46:08 -0700
commita5af5aa8b67dfdba36c853b70564fd2dfe73d478 (patch)
treed898e560802ef68b21280539040ccd19dc62678b /mm
parentfanotify: fix event filtering with FAN_ONDIR set (diff)
kasan, module, vmalloc: rework shadow allocation for modules
Current approach in handling shadow memory for modules is broken. Shadow memory could be freed only after memory shadow corresponds it is no longer used. vfree() called from interrupt context could use memory its freeing to store 'struct llist_node' in it: void vfree(const void *addr) { ... if (unlikely(in_interrupt())) { struct vfree_deferred *p = this_cpu_ptr(&vfree_deferred); if (llist_add((struct llist_node *)addr, &p->list)) schedule_work(&p->wq); Later this list node used in free_work() which actually frees memory. Currently module_memfree() called in interrupt context will free shadow before freeing module's memory which could provoke kernel crash. So shadow memory should be freed after module's memory. However, such deallocation order could race with kasan_module_alloc() in module_alloc(). Free shadow right before releasing vm area. At this point vfree()'d memory is not used anymore and yet not available for other allocations. New VM_KASAN flag used to indicate that vm area has dynamically allocated shadow memory so kasan frees shadow only if it was previously allocated. Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com> Acked-by: Rusty Russell <rusty@rustcorp.com.au> Cc: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
2 files changed, 12 insertions, 3 deletions
diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 78fee632a7ee..936d81661c47 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -29,6 +29,7 @@
#include <linux/stacktrace.h>
#include <linux/string.h>
#include <linux/types.h>
+#include <linux/vmalloc.h>
#include <linux/kasan.h>
#include "kasan.h"
@@ -414,12 +415,19 @@ int kasan_module_alloc(void *addr, size_t size)
- return ret ? 0 : -ENOMEM;
+ if (ret) {
+ find_vm_area(addr)->flags |= VM_KASAN;
+ return 0;
+ }
+ return -ENOMEM;
-void kasan_module_free(void *addr)
+void kasan_free_shadow(const struct vm_struct *vm)
- vfree(kasan_mem_to_shadow(addr));
+ if (vm->flags & VM_KASAN)
+ vfree(kasan_mem_to_shadow(vm->addr));
static void register_global(struct kasan_global *global)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 35b25e1340ca..49abccf29a29 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1418,6 +1418,7 @@ struct vm_struct *remove_vm_area(const void *addr)
vmap_debug_free_range(va->va_start, va->va_end);
+ kasan_free_shadow(vm);
vm->size -= PAGE_SIZE;