From cac9b9a4b08304f11daace03b8b48659355e44c1 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 18 Jul 2019 10:47:47 +0200 Subject: [PATCH] stacktrace: Force USER_DS for stack_trace_save_user() When walking userspace stacks, USER_DS needs to be set, otherwise access_ok() will not function as expected. Reported-by: Vegard Nossum Reported-by: Eiichi Tsukata Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Tested-by: Vegard Nossum Reviewed-by: Joel Fernandes (Google) Link: https://lkml.kernel.org/r/20190718085754.GM3402@hirez.programming.kicks-ass.net --- kernel/stacktrace.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c index e6a02b274b73..f5440abb7532 100644 --- a/kernel/stacktrace.c +++ b/kernel/stacktrace.c @@ -226,12 +226,17 @@ unsigned int stack_trace_save_user(unsigned long *store, unsigned int size) .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 -- 2.30.2