Re: [PATCH mm 03/22] kasan: rearrange stack frame info in reports

[Alexander Potapenko <glider@xxxxxxxxxx>]

On Wed, Mar 2, 2022 at 5:36 PM <andrey.konovalov@xxxxxxxxx> wrote:

From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>

- Move printing stack frame info before printing page info.

- Add object_is_on_stack() check to print_address_description()
  and add a corresponding WARNING to kasan_print_address_stack_frame().
  This looks more in line with the rest of the checks in this function
  and also allows to avoid complicating code logic wrt line breaks.

- Clean up comments related to get_address_stack_frame_info().

Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>

Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx> 

---
 mm/kasan/report.c         | 12 +++++++++---
 mm/kasan/report_generic.c | 15 ++++-----------
 2 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index ded648c0a0e4..d60ee8b81e2b 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -259,6 +259,15 @@ static void print_address_description(void *addr, u8 tag)
                pr_err("\n");
        }

+       if (object_is_on_stack(addr)) {
+               /*
+                * Currently, KASAN supports printing frame information only
+                * for accesses to the task's own stack.
+                */
+               kasan_print_address_stack_frame(addr);
+               pr_err("\n");
+       }
+
        if (is_vmalloc_addr(addr)) {
                struct vm_struct *va = find_vm_area(addr);

@@ -278,9 +287,6 @@ static void print_address_description(void *addr, u8 tag)
                dump_page(page, "kasan: bad access detected");
                pr_err("\n");
        }
-
-       kasan_print_address_stack_frame(addr);
-       pr_err("\n");
 }

 static bool meta_row_is_guilty(const void *row, const void *addr)
diff --git a/mm/kasan/report_generic.c b/mm/kasan/report_generic.c
index 139615ef326b..3751391ff11a 100644
--- a/mm/kasan/report_generic.c
+++ b/mm/kasan/report_generic.c
@@ -211,6 +211,7 @@ static void print_decoded_frame_descr(const char *frame_descr)
        }
 }

+/* Returns true only if the address is on the current task's stack. */
 static bool __must_check get_address_stack_frame_info(const void *addr,
                                                      unsigned long *offset,
                                                      const char **frame_descr,
@@ -224,13 +225,6 @@ static bool __must_check get_address_stack_frame_info(const void *addr,

        BUILD_BUG_ON(IS_ENABLED(CONFIG_STACK_GROWSUP));

-       /*
-        * NOTE: We currently only support printing frame information for
-        * accesses to the task's own stack.
-        */
-       if (!object_is_on_stack(addr))
-               return false;
-
        aligned_addr = round_down((unsigned long)addr, sizeof(long));
        mem_ptr = round_down(aligned_addr, KASAN_GRANULE_SIZE);
        shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr);
@@ -269,14 +263,13 @@ void kasan_print_address_stack_frame(const void *addr)
        const char *frame_descr;
        const void *frame_pc;

+       if (WARN_ON(!object_is_on_stack(addr)))
+               return;
+
        if (!get_address_stack_frame_info(addr, &offset, &frame_descr,
                                          &frame_pc))
                return;

-       /*
-        * get_address_stack_frame_info only returns true if the given addr is
-        * on the current task's stack.
-        */
        pr_err("\n");
        pr_err("addr %px is located in stack of task %s/%d at offset %lu in frame:\n",
               addr, current->comm, task_pid_nr(current), offset);
--
2.25.1

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Alexander Potapenko
Software Engineer

Google Germany GmbH
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