On Wed, Jul 01, 2020 at 11:08:57PM +0900, Tetsuo Handa wrote: > On 2020/07/01 22:53, Luis Chamberlain wrote: > >> Well, it is not br_stp_call_user() but br_stp_start() which is expecting > >> to set sub_info->retval for both KWIFEXITED() case and KWIFSIGNALED() case. > >> That is, sub_info->retval needs to carry raw value (i.e. without "umh: fix > >> processed error when UMH_WAIT_PROC is used" will be the correct behavior). > > > > br_stp_start() doesn't check for the raw value, it just checks for err > > or !err. So the patch, "umh: fix processed error when UMH_WAIT_PROC is > > used" propagates the correct error now. > > No. If "/sbin/bridge-stp virbr0 start" terminated due to e.g. SIGSEGV > (for example, by inserting "kill -SEGV $$" into right after "#!/bin/sh" line), > br_stp_start() needs to select BR_KERNEL_STP path. We can't assume that > /sbin/bridge-stp is always terminated by exit() syscall (and hence we can't > ignore KWIFSIGNALED() case in call_usermodehelper_exec_sync()). Ah, well that would be a different fix required, becuase again, br_stp_start() does not untangle the correct error today really. I also I think it would be odd odd that SIGSEGV or another signal is what was terminating Christian's bridge stp call, but let's find out! Note we pass 0 to the options to wait so the mistake here could indeed be that we did not need KWIFSIGNALED(). I was afraid of this prospect... as it other implications. It means we either *open code* all callers, or we handle this in a unified way on the umh. And if we do handle this in a unified way, it then begs the question as to *what* do we pass for the signals case and continued case. Below we just pass the signal, and treat continued as OK, but treating continued as OK would also be a *new* change as well. For instance (this goes just boot tested, but Christian if you can try this as well that would be appreciated): diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h index bba06befbff5..d1898f5dd1fc 100644 --- a/include/linux/sched/task.h +++ b/include/linux/sched/task.h @@ -105,10 +105,12 @@ extern long kernel_wait4(pid_t, int __user *, int, struct rusage *); /* Only add helpers for actual use cases in the kernel */ #define KWEXITSTATUS(status) (__KWEXITSTATUS(status)) +#define KWTERMSIG(status) (__KWTERMSIG(status)) +#define KWSTOPSIG(status) (__KWSTOPSIG(status)) #define KWIFEXITED(status) (__KWIFEXITED(status)) - -/* Nonzero if STATUS indicates normal termination. */ -#define __KWIFEXITED(status) (__KWTERMSIG(status) == 0) +#define KWIFSIGNALED(status) (__KWIFSIGNALED(status)) +#define KWIFSTOPPED(status) (__KWIFSTOPPED(status)) +#define KWIFCONTINUED(status) (__KWIFCONTINUED(status)) /* If KWIFEXITED(STATUS), the low-order 8 bits of the status. */ #define __KWEXITSTATUS(status) (((status) & 0xff00) >> 8) @@ -116,6 +118,24 @@ extern long kernel_wait4(pid_t, int __user *, int, struct rusage *); /* If KWIFSIGNALED(STATUS), the terminating signal. */ #define __KWTERMSIG(status) ((status) & 0x7f) +/* If KWIFSTOPPED(STATUS), the signal that stopped the child. */ +#define __KWSTOPSIG(status) __KWEXITSTATUS(status) + +/* Nonzero if STATUS indicates normal termination. */ +#define __KWIFEXITED(status) (__KWTERMSIG(status) == 0) + +/* Nonzero if STATUS indicates termination by a signal. */ +#define __KWIFSIGNALED(status) \ + (((signed char) (((status) & 0x7f) + 1) >> 1) > 0) + +/* Nonzero if STATUS indicates the child is stopped. */ +#define __KWIFSTOPPED(status) (((status) & 0xff) == 0x7f) + +/* Nonzero if STATUS indicates the child continued after a stop. */ +#define __KWIFCONTINUED(status) ((status) == __KW_CONTINUED) + +#define __KW_CONTINUED 0xffff + extern void free_task(struct task_struct *tsk); /* sched_exec is called by processes performing an exec */ diff --git a/kernel/umh.c b/kernel/umh.c index f81e8698e36e..c98fb1ed90c9 100644 --- a/kernel/umh.c +++ b/kernel/umh.c @@ -156,6 +156,18 @@ static void call_usermodehelper_exec_sync(struct subprocess_info *sub_info) */ if (KWIFEXITED(ret)) sub_info->retval = KWEXITSTATUS(ret); + /* + * Do we really want to be passing the signal, or do we pass + * a single error code for all cases? + */ + else if (KWIFSIGNALED(ret)) + sub_info->retval = KWTERMSIG(ret); + /* Same here */ + else if (KWIFSTOPPED((ret))) + sub_info->retval = KWSTOPSIG(ret); + /* And are we really sure we want this? */ + else if (KWIFCONTINUED((ret))) + sub_info->retval = 0; } /* Restore default kernel sig handler */
