open08: calling tst_get_bad_addr from LTP API

From open(2) manual, pathname(unmapped_fname) points outside the accessible address space, then test will result in failure with EFAULT.

LTP tst_get_bad_addr() maps a "guard-page" by using PROT_NONE to provides page not be accessed too. Here we can take use of it to achieve the same purpose.

Signed-off-by Li Wang <[email protected]>

---

Notes:
Jan,

I'm sorry I didn't think of that function in LTP API when reveiwed your open08 patch.

Here I propose to remove the get_invalid_addr() from open08.c.

Li Wang

 testcases/kernel/syscalls/open/open08.c | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

testcases/kernel/syscalls/open/open08.c +2 -13

index 5b24752..c407332 100644
@@ -58,6 +58,7 @@
 #include <signal.h>
 #include <pwd.h>
 #include "tst_test.h"
+#include "tst_get_bad_addr.h"
 
 static char *existing_fname = "open08_testfile";
 static char *toolong_fname = "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstmnopqrstuvwxyzabcdefghijklmnopqrstmnopqrstuvwxyzabcdefghijklmnopqrstmnopqrstuvwxyzabcdefghijklmnopqrstmnopqrstuvwxyzabcdefghijklmnopqrstmnopqrstuvwxyzabcdefghijklmnopqrstmnopqrstuvwxyz";

@@ -101,17 +102,6 @@ void verify_open(unsigned int i)
        }
 }
 
-static void *get_invalid_addr(void)
-{
-       char *bad_addr;
-       int len = 2 * 1024 * 1024;
-
-       bad_addr = SAFE_MMAP(0, len, PROT_READ|PROT_WRITE,
-               MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
-       SAFE_MUNMAP(bad_addr, len);
-       return bad_addr + len/2;
-}
-
 static void setup(void)
 {
        int fildes;

@@ -130,7 +120,7 @@ static void setup(void)
        fildes = SAFE_CREAT(existing_fname, 0600);
        close(fildes);
 
-       unmapped_fname = get_invalid_addr();
+       unmapped_fname = tst_get_bad_addr(NULL);
 }
 
 static struct tst_test test = {
--

2.9.5

--
Mailing list info: https://lists.linux.it/listinfo/ltp

Maybe we misled by the code comments before, after thinking over, I guess the "outside your accessible address space" != "outside of process mapped space". So we don't need to do map/unmap to satisfy that.

----- Original Message -----

Quoted 4 lines

Maybe we misled by the code comments before, after thinking over, I guess the "outside your accessible address space" != "outside of process mapped space". So we don't need to do map/unmap to satisfy that.

That may be the case, I changed it on purpose to match that comment. Though as you pointed out PROT_NONE might be enough too.

Is the motivation for your patch to re-use existing function

or have you hit some problem with map/unmap?

Regards,
Jan

Quoted 8 lines

----- Original Message -----

Quoted 4 lines

Maybe we misled by the code comments before, after thinking over, I guess the "outside your accessible address space" != "outside of process mapped space". So we don't need to do map/unmap to satisfy that.

Quoted 4 lines

That may be the case, I changed it on purpose to match that comment. Though as you pointed out PROT_NONE might be enough too.

Is the motivation for your patch to re-use existing function

Yes, firstly my motivation is to re-use the existing function. But then I realized that maybe the original author misunderst
​oo​
d the EFAULT error in open().

So I find open(2) manual and get this:
"EFAULT pathname points outside your *accessible* address space."

​Then I think maybe we need match the manual but not the code comments.

----- Original Message -----

Quoted 1 line

On Wed, Jul 11, 2018 at 3:28 PM, Jan Stancek <[email protected]>

Quoted 18 lines · wrote:

Quoted 8 lines

----- Original Message -----

Quoted 4 lines

Maybe we misled by the code comments before, after thinking over, I guess the "outside your accessible address space" != "outside of process mapped space". So we don't need to do map/unmap to satisfy that.

Quoted 4 lines

That may be the case, I changed it on purpose to match that comment. Though as you pointed out PROT_NONE might be enough too.

Is the motivation for your patch to re-use existing function

Yes, firstly my motivation is to re-use the existing function. But then I realized that maybe the original author misunderst
​oo​
d the EFAULT error in open().

Quoted 4 lines

So I find open(2) manual and get this:
"EFAULT pathname points outside your *accessible* address space."

​Then I think maybe we need match the manual but not the code comments.

I'd say we match it already (in stronger form than PROT_NONE).

I don't object to re-using LTP function. Can you send v2 that updates also the comment please?

Regards,
Jan