Messages in this thread Patch in this message | | | From | Kees Cook <> | Subject | [PATCH 1/4] syscalls: Use CHECK_DATA_CORRUPTION for addr_limit_user_check | Date | Thu, 7 Sep 2017 08:30:44 -0700 |
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From: Thomas Garnier <thgarnie@google.com>
Use CHECK_DATA_CORRUPTION instead of BUG_ON to provide more flexibility on address limit failures. By default, send a SIGKILL signal to kill the current process preventing exploitation of a bad address limit.
Make the TIF_FSCHECK flag optional so ARM can use this function.
Signed-off-by: Thomas Garnier <thgarnie@google.com> Signed-off-by: Kees Cook <keescook@chromium.org> --- include/linux/syscalls.h | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 88951b795ee3..65e273aadada 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -219,21 +219,25 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event) } \ static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__)) -#ifdef TIF_FSCHECK /* * Called before coming back to user-mode. Returning to user-mode with an * address limit different than USER_DS can allow to overwrite kernel memory. */ static inline void addr_limit_user_check(void) { - +#ifdef TIF_FSCHECK if (!test_thread_flag(TIF_FSCHECK)) return; +#endif - BUG_ON(!segment_eq(get_fs(), USER_DS)); + if (CHECK_DATA_CORRUPTION(!segment_eq(get_fs(), USER_DS), + "Invalid address limit on user-mode return")) + force_sig(SIGKILL, current); + +#ifdef TIF_FSCHECK clear_thread_flag(TIF_FSCHECK); -} #endif +} asmlinkage long sys32_quotactl(unsigned int cmd, const char __user *special, qid_t id, void __user *addr); -- 2.7.4
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