Re: [PATCH 1/1] mm/madvise: replace ptrace attach requirement for process_madvise

On Fri, Jan 8, 2021 at 5:02 PM David Rientjes [off-list ref] wrote:

On Fri, 8 Jan 2021, Suren Baghdasaryan wrote:

quoted

quoted

quoted

@@ -1197,12 +1197,22 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
              goto release_task;
      }

-     mm = mm_access(task, PTRACE_MODE_ATTACH_FSCREDS);
+     /* Require PTRACE_MODE_READ to avoid leaking ASLR metadata. */
+     mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
      if (IS_ERR_OR_NULL(mm)) {
              ret = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
              goto release_task;
      }

+     /*
+      * Require CAP_SYS_NICE for influencing process performance. Note that
+      * only non-destructive hints are currently supported.
+      */
+     if (!capable(CAP_SYS_NICE)) {
+             ret = -EPERM;
+             goto release_task;

mmput?

Ouch! Thanks for pointing it out! Will include in the next respin.

With the fix, feel free to add:

        Acked-by: David Rientjes [off-list ref]

Thanks! Will post a new version with the fix on Monday.

Thanks Suren!