From: Peter Zijlstra <peterz@xxxxxxxxxxxxx> [ Upstream commit cac9b9a4b08304f11daace03b8b48659355e44c1 ] When walking userspace stacks, USER_DS needs to be set, otherwise access_ok() will not function as expected. Reported-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx> Reported-by: Eiichi Tsukata <devel@xxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Tested-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx> Reviewed-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20190718085754.GM3402@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- kernel/stacktrace.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c index 36139de0a3c4..899b726c9e98 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->mm) 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 -- 2.20.1
