From: Peter Zijlstra peterz@infradead.org
[ 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@oracle.com Reported-by: Eiichi Tsukata devel@etsukata.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Signed-off-by: Thomas Gleixner tglx@linutronix.de Tested-by: Vegard Nossum vegard.nossum@oracle.com Reviewed-by: Joel Fernandes (Google) joel@joelfernandes.org Link: https://lkml.kernel.org/r/20190718085754.GM3402@hirez.programming.kicks-ass.... Signed-off-by: Sasha Levin sashal@kernel.org --- 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