Merge branch 'akpm' (patches from Andrew)

Merge misc fixes from Andrew Morton:
 "28 patches.

  Subsystems affected by this series: mm (memblock, pagealloc, hugetlb,
  highmem, kfence, oom-kill, madvise, kasan, userfaultfd, memcg, and
  zram), core-kernel, kconfig, fork, binfmt, MAINTAINERS, kbuild, and
  ia64"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (28 commits)
  zram: fix broken page writeback
  zram: fix return value on writeback_store
  mm/memcg: set memcg when splitting page
  mm/memcg: rename mem_cgroup_split_huge_fixup to split_page_memcg and add nr_pages argument
  ia64: fix ptrace(PTRACE_SYSCALL_INFO_EXIT) sign
  ia64: fix ia64_syscall_get_set_arguments() for break-based syscalls
  mm/userfaultfd: fix memory corruption due to writeprotect
  kasan: fix KASAN_STACK dependency for HW_TAGS
  kasan, mm: fix crash with HW_TAGS and DEBUG_PAGEALLOC
  mm/madvise: replace ptrace attach requirement for process_madvise
  include/linux/sched/mm.h: use rcu_dereference in in_vfork()
  kfence: fix reports if constant function prefixes exist
  kfence, slab: fix cache_alloc_debugcheck_after() for bulk allocations
  kfence: fix printk format for ptrdiff_t
  linux/compiler-clang.h: define HAVE_BUILTIN_BSWAP*
  MAINTAINERS: exclude uapi directories in API/ABI section
  binfmt_misc: fix possible deadlock in bm_register_write
  mm/highmem.c: fix zero_user_segments() with start > end
  hugetlb: do early cow when page pinned on src mm
  mm: use is_cow_mapping() across tree where proper
  ...

1 files changed, 12 insertions, 1 deletions

diff --git a/mm/madvise.c b/mm/madvise.c
index df692d2e35d4..01fef79ac761 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1198,12 +1198,22 @@ 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_mm;
+	}
+
 	total_len = iov_iter_count(&iter);
 
 	while (iov_iter_count(&iter)) {
@@ -1218,6 +1228,7 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
 	if (ret == 0)
 		ret = total_len - iov_iter_count(&iter);
 
+release_mm:
 	mmput(mm);
 release_task:
 	put_task_struct(task);