On Wed, Jul 17, 2019 at 10:09:45AM +0200, Vegard Nossum wrote: > On 7/17/19 10:07 AM, Peter Zijlstra wrote:
> > Does something like the below help? > Yes. Thanks! --- Subject: stacktrace: Force USER_DS for stack_trace_save_user() From: Peter Zijlstra <pet...@infradead.org> Date: Thu Jul 18 10:47:47 CEST 2019 When walking userspace stacks, we should set USER_DS, otherwise access_ok() will not function as expected. Reported-by: Vegard Nossum <vegard.nos...@oracle.com> Tested-by: Vegard Nossum <vegard.nos...@oracle.com> Reported-by: Eiichi Tsukata <de...@etsukata.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> --- --- a/kernel/stacktrace.c +++ b/kernel/stacktrace.c @@ -226,12 +226,17 @@ unsigned int stack_trace_save_user(unsig .store = store, .size = size, }; + mm_segment_t fs; /* Trace user stack if not a kernel thread */ if (current->flags & PF_KTHREAD) return 0; + fs = get_fs(); + set_fs(USER_DS); arch_stack_walk_user(consume_entry, &c, task_pt_regs(current)); + set_fs(fs); + return c.len; } #endif