diff options
| author | Jann Horn <jannh@google.com> | 2019-05-29 13:31:57 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-06-19 08:20:55 +0200 |
| commit | 7013ea8df35d3078b286aa8b99bf868c24c92ca5 (patch) | |
| tree | 3925e76a6eec6b72f0cc2e70a202e8bf59654881 /kernel/ptrace.c | |
| parent | 50f806a53964577d43c4fbb7b35416fe3d317105 (diff) | |
ptrace: restore smp_rmb() in __ptrace_may_access()
commit f6581f5b55141a95657ef5742cf6a6bfa20a109f upstream.
Restore the read memory barrier in __ptrace_may_access() that was deleted
a couple years ago. Also add comments on this barrier and the one it pairs
with to explain why they're there (as far as I understand).
Fixes: bfedb589252c ("mm: Add a user_ns owner to mm_struct and fix ptrace permission checks")
Cc: stable@vger.kernel.org
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel/ptrace.c')
| -rw-r--r-- | kernel/ptrace.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/kernel/ptrace.c b/kernel/ptrace.c index f6b452e3c204..a75959dc149e 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -323,6 +323,16 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode) return -EPERM; ok: rcu_read_unlock(); + /* + * If a task drops privileges and becomes nondumpable (through a syscall + * like setresuid()) while we are trying to access it, we must ensure + * that the dumpability is read after the credentials; otherwise, + * we may be able to attach to a task that we shouldn't be able to + * attach to (as if the task had dropped privileges without becoming + * nondumpable). + * Pairs with a write barrier in commit_creds(). + */ + smp_rmb(); mm = task->mm; if (mm && ((get_dumpable(mm) != SUID_DUMP_USER) && |