The code here uses a struct waitid_info to catch basic information about process exit including the pid, uid, status, and signal that caused the process to exit. This information is then stuffed into a struct siginfo for the waitid() syscall. That seems like an odd thing to do. We can just pass down a siginfo_t struct directly which let's us cleanup and simplify the whole code quite a bit. This patch also simplifies the following implementation of pidfd_wait().
Note that this changes how struct siginfo is filled in for users of waitid. POSIX doesn't mandate anything else other than si_pid, si_uid, si_code, and si_signo. So it seems up to the implementation. In case anyone relies on the old behavior we can just revert but I highly doubt that users fill in siginfo_t before a call to waitid and expect all fields other then the ones mention above to be untouched. Signed-off-by: Christian Brauner <[email protected]> Cc: Arnd Bergmann <[email protected]> Cc: "Eric W. Biederman" <[email protected]> Cc: Kees Cook <[email protected]> Cc: Joel Fernandes (Google) <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Tejun Heo <[email protected]> Cc: David Howells <[email protected]> Cc: Jann Horn <[email protected]> Cc: Andy Lutomirsky <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: Aleksa Sarai <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Al Viro <[email protected]> --- kernel/exit.c | 101 ++++++++++++++++++-------------------------------- 1 file changed, 36 insertions(+), 65 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index a75b6a7f458a..73392a455b72 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -994,19 +994,12 @@ SYSCALL_DEFINE1(exit_group, int, error_code) return 0; } -struct waitid_info { - pid_t pid; - uid_t uid; - int status; - int cause; -}; - struct wait_opts { enum pid_type wo_type; int wo_flags; struct pid *wo_pid; - struct waitid_info *wo_info; + kernel_siginfo_t *wo_info; int wo_stat; struct rusage *wo_rusage; @@ -1058,7 +1051,7 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p) int state, status; pid_t pid = task_pid_vnr(p); uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p)); - struct waitid_info *infop; + kernel_siginfo_t *infop; if (!likely(wo->wo_flags & WEXITED)) return 0; @@ -1169,14 +1162,14 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p) infop = wo->wo_info; if (infop) { if ((status & 0x7f) == 0) { - infop->cause = CLD_EXITED; - infop->status = status >> 8; + infop->si_code = CLD_EXITED; + infop->si_status = status >> 8; } else { - infop->cause = (status & 0x80) ? CLD_DUMPED : CLD_KILLED; - infop->status = status & 0x7f; + infop->si_code = (status & 0x80) ? CLD_DUMPED : CLD_KILLED; + infop->si_status = status & 0x7f; } - infop->pid = pid; - infop->uid = uid; + infop->si_pid = pid; + infop->si_uid = uid; } return pid; @@ -1215,7 +1208,7 @@ static int *task_stopped_code(struct task_struct *p, bool ptrace) static int wait_task_stopped(struct wait_opts *wo, int ptrace, struct task_struct *p) { - struct waitid_info *infop; + kernel_siginfo_t *infop; int exit_code, *p_code, why; uid_t uid = 0; /* unneeded, required by compiler */ pid_t pid; @@ -1270,10 +1263,10 @@ static int wait_task_stopped(struct wait_opts *wo, infop = wo->wo_info; if (infop) { - infop->cause = why; - infop->status = exit_code; - infop->pid = pid; - infop->uid = uid; + infop->si_code = why; + infop->si_status = exit_code; + infop->si_pid = pid; + infop->si_uid = uid; } return pid; } @@ -1286,7 +1279,7 @@ static int wait_task_stopped(struct wait_opts *wo, */ static int wait_task_continued(struct wait_opts *wo, struct task_struct *p) { - struct waitid_info *infop; + kernel_siginfo_t *infop; pid_t pid; uid_t uid; @@ -1316,13 +1309,13 @@ static int wait_task_continued(struct wait_opts *wo, struct task_struct *p) put_task_struct(p); infop = wo->wo_info; - if (!infop) { - wo->wo_stat = 0xffff; + if (infop) { + infop->si_code = CLD_CONTINUED; + infop->si_status = SIGCONT; + infop->si_pid = pid; + infop->si_uid = uid; } else { - infop->cause = CLD_CONTINUED; - infop->pid = pid; - infop->uid = uid; - infop->status = SIGCONT; + wo->wo_stat = 0xffff; } return pid; } @@ -1552,7 +1545,7 @@ static long do_wait(struct wait_opts *wo) return retval; } -static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop, +static long kernel_waitid(int which, pid_t upid, kernel_siginfo_t *infop, int options, struct rusage *ru) { struct wait_opts wo; @@ -1602,33 +1595,22 @@ SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *, infop, int, options, struct rusage __user *, ru) { struct rusage r; - struct waitid_info info = {.status = 0}; - long err = kernel_waitid(which, upid, &info, options, ru ? &r : NULL); - int signo = 0; - + kernel_siginfo_t kinfo = { + .si_signo = 0, + }; + long err = kernel_waitid(which, upid, infop ? &kinfo : NULL, options, + ru ? &r : NULL); if (err > 0) { - signo = SIGCHLD; + kinfo.si_signo = SIGCHLD; err = 0; if (ru && copy_to_user(ru, &r, sizeof(struct rusage))) return -EFAULT; } - if (!infop) - return err; - if (!user_access_begin(infop, sizeof(*infop))) + if (infop && copy_siginfo_to_user(infop, &kinfo)) return -EFAULT; - unsafe_put_user(signo, &infop->si_signo, Efault); - unsafe_put_user(0, &infop->si_errno, Efault); - unsafe_put_user(info.cause, &infop->si_code, Efault); - unsafe_put_user(info.pid, &infop->si_pid, Efault); - unsafe_put_user(info.uid, &infop->si_uid, Efault); - unsafe_put_user(info.status, &infop->si_status, Efault); - user_access_end(); - return err; -Efault: - user_access_end(); - return -EFAULT; + return err ; } long kernel_wait4(pid_t upid, int __user *stat_addr, int options, @@ -1722,11 +1704,13 @@ COMPAT_SYSCALL_DEFINE5(waitid, struct compat_rusage __user *, uru) { struct rusage ru; - struct waitid_info info = {.status = 0}; - long err = kernel_waitid(which, pid, &info, options, uru ? &ru : NULL); - int signo = 0; + kernel_siginfo_t kinfo = { + .si_signo = 0, + }; + long err = kernel_waitid(which, pid, infop ? &kinfo : NULL, options, + uru ? &ru : NULL); if (err > 0) { - signo = SIGCHLD; + kinfo.si_signo = SIGCHLD; err = 0; if (uru) { /* kernel_waitid() overwrites everything in ru */ @@ -1739,23 +1723,10 @@ COMPAT_SYSCALL_DEFINE5(waitid, } } - if (!infop) - return err; - - if (!user_access_begin(infop, sizeof(*infop))) + if (infop && copy_siginfo_to_user32(infop, &kinfo)) return -EFAULT; - unsafe_put_user(signo, &infop->si_signo, Efault); - unsafe_put_user(0, &infop->si_errno, Efault); - unsafe_put_user(info.cause, &infop->si_code, Efault); - unsafe_put_user(info.pid, &infop->si_pid, Efault); - unsafe_put_user(info.uid, &infop->si_uid, Efault); - unsafe_put_user(info.status, &infop->si_status, Efault); - user_access_end(); return err; -Efault: - user_access_end(); - return -EFAULT; } #endif -- 2.22.0
