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waitid(2): leave copyout of siginfo to syscall itself

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have kernel_waitid() collect the information needed for siginfo into
a small structure (waitid_info) passed to it; deal with copyout in
sys_waitid()/compat_sys_waitid().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2017-05-14 20:53:13 -04:00
parent 359566faef
commit 67d7ddded3
1 changed files with 64 additions and 104 deletions
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168
kernel/exit.c
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@ -996,12 +996,19 @@ SYSCALL_DEFINE1(exit_group, int, error_code)
return 0; return 0;
} }
struct waitid_info {
pid_t pid;
uid_t uid;
int status;
int cause;
};
struct wait_opts { struct wait_opts {
enum pid_type wo_type; enum pid_type wo_type;
int wo_flags; int wo_flags;
struct pid *wo_pid; struct pid *wo_pid;
struct siginfo __user *wo_info; struct waitid_info *wo_info;
int wo_stat; int wo_stat;
struct rusage *wo_rusage; struct rusage *wo_rusage;
@ -1053,8 +1060,7 @@ eligible_child(struct wait_opts *wo, bool ptrace, struct task_struct *p)
static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p, static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
pid_t pid, uid_t uid, int why, int status) pid_t pid, uid_t uid, int why, int status)
{ {
struct siginfo __user *infop; struct waitid_info *infop;
int retval = 0;
if (wo->wo_rusage) if (wo->wo_rusage)
getrusage(p, RUSAGE_BOTH, wo->wo_rusage); getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
@ -1062,22 +1068,12 @@ static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
put_task_struct(p); put_task_struct(p);
infop = wo->wo_info; infop = wo->wo_info;
if (infop) { if (infop) {
if (!retval) infop->cause = why;
retval = put_user(SIGCHLD, &infop->si_signo); infop->pid = pid;
if (!retval) infop->uid = uid;
retval = put_user(0, &infop->si_errno); infop->status = status;
if (!retval)
retval = put_user((short)why, &infop->si_code);
if (!retval)
retval = put_user(pid, &infop->si_pid);
if (!retval)
retval = put_user(uid, &infop->si_uid);
if (!retval)
retval = put_user(status, &infop->si_status);
} }
if (!retval) return pid;
retval = pid;
return retval;
} }
/* /*
@ -1088,10 +1084,10 @@ static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
*/ */
static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p) static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
{ {
int state, retval, status; int state, status;
pid_t pid = task_pid_vnr(p); pid_t pid = task_pid_vnr(p);
uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p)); uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
struct siginfo __user *infop; struct waitid_info *infop;
if (!likely(wo->wo_flags & WEXITED)) if (!likely(wo->wo_flags & WEXITED))
return 0; return 0;
@ -1186,36 +1182,22 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
if (wo->wo_rusage) if (wo->wo_rusage)
getrusage(p, RUSAGE_BOTH, wo->wo_rusage); getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
retval = 0;
status = (p->signal->flags & SIGNAL_GROUP_EXIT) status = (p->signal->flags & SIGNAL_GROUP_EXIT)
? p->signal->group_exit_code : p->exit_code; ? p->signal->group_exit_code : p->exit_code;
wo->wo_stat = status; wo->wo_stat = status;
infop = wo->wo_info; infop = wo->wo_info;
if (!retval && infop) if (infop) {
retval = put_user(SIGCHLD, &infop->si_signo);
if (!retval && infop)
retval = put_user(0, &infop->si_errno);
if (!retval && infop) {
int why;
if ((status & 0x7f) == 0) { if ((status & 0x7f) == 0) {
why = CLD_EXITED; infop->cause = CLD_EXITED;
status >>= 8; infop->status = status >> 8;
} else { } else {
why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED; infop->cause = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
status &= 0x7f; infop->status = status & 0x7f;
} }
retval = put_user((short)why, &infop->si_code); infop->pid = pid;
if (!retval) infop->uid = uid;
retval = put_user(status, &infop->si_status);
} }
if (!retval && infop)
retval = put_user(pid, &infop->si_pid);
if (!retval && infop)
retval = put_user(uid, &infop->si_uid);
if (!retval)
retval = pid;
if (state == EXIT_TRACE) { if (state == EXIT_TRACE) {
write_lock_irq(&tasklist_lock); write_lock_irq(&tasklist_lock);
@ -1232,7 +1214,7 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
if (state == EXIT_DEAD) if (state == EXIT_DEAD)
release_task(p); release_task(p);
return retval; return pid;
} }
static int *task_stopped_code(struct task_struct *p, bool ptrace) static int *task_stopped_code(struct task_struct *p, bool ptrace)
@ -1268,8 +1250,8 @@ static int *task_stopped_code(struct task_struct *p, bool ptrace)
static int wait_task_stopped(struct wait_opts *wo, static int wait_task_stopped(struct wait_opts *wo,
int ptrace, struct task_struct *p) int ptrace, struct task_struct *p)
{ {
struct siginfo __user *infop; struct waitid_info *infop;
int retval, exit_code, *p_code, why; int exit_code, *p_code, why;
uid_t uid = 0; /* unneeded, required by compiler */ uid_t uid = 0; /* unneeded, required by compiler */
pid_t pid; pid_t pid;
@ -1320,28 +1302,19 @@ unlock_sig:
if (wo->wo_rusage) if (wo->wo_rusage)
getrusage(p, RUSAGE_BOTH, wo->wo_rusage); getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
retval = 0;
wo->wo_stat = (exit_code << 8) | 0x7f; wo->wo_stat = (exit_code << 8) | 0x7f;
infop = wo->wo_info; infop = wo->wo_info;
if (!retval && infop) if (infop) {
retval = put_user(SIGCHLD, &infop->si_signo); infop->cause = why;
if (!retval && infop) infop->status = exit_code;
retval = put_user(0, &infop->si_errno); infop->pid = pid;
if (!retval && infop) infop->uid = uid;
retval = put_user((short)why, &infop->si_code); }
if (!retval && infop)
retval = put_user(exit_code, &infop->si_status);
if (!retval && infop)
retval = put_user(pid, &infop->si_pid);
if (!retval && infop)
retval = put_user(uid, &infop->si_uid);
if (!retval)
retval = pid;
put_task_struct(p); put_task_struct(p);
BUG_ON(!retval); BUG_ON(!pid);
return retval; return pid;
} }
/* /*
@ -1618,7 +1591,7 @@ end:
return retval; return retval;
} }
static long kernel_waitid(int which, pid_t upid, struct siginfo __user *infop, static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop,
int options, struct rusage *ru) int options, struct rusage *ru)
{ {
struct wait_opts wo; struct wait_opts wo;
@ -1660,27 +1633,8 @@ static long kernel_waitid(int which, pid_t upid, struct siginfo __user *infop,
wo.wo_rusage = ru; wo.wo_rusage = ru;
ret = do_wait(&wo); ret = do_wait(&wo);
if (ret > 0) { if (ret > 0)
ret = 0; ret = 0;
} else if (infop) {
/*
* For a WNOHANG return, clear out all the fields
* we would set so the user can easily tell the
* difference.
*/
if (!ret)
ret = put_user(0, &infop->si_signo);
if (!ret)
ret = put_user(0, &infop->si_errno);
if (!ret)
ret = put_user(0, &infop->si_code);
if (!ret)
ret = put_user(0, &infop->si_pid);
if (!ret)
ret = put_user(0, &infop->si_uid);
if (!ret)
ret = put_user(0, &infop->si_status);
}
put_pid(pid); put_pid(pid);
return ret; return ret;
@ -1690,12 +1644,24 @@ SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
infop, int, options, struct rusage __user *, ru) infop, int, options, struct rusage __user *, ru)
{ {
struct rusage r; struct rusage r;
long err = kernel_waitid(which, upid, infop, options, ru ? &r : NULL); struct waitid_info info = {.status = 0};
long err = kernel_waitid(which, upid, &info, options, ru ? &r : NULL);
if (!err) { if (!err) {
if (ru && copy_to_user(ru, &r, sizeof(struct rusage))) if (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
return -EFAULT; return -EFAULT;
} }
if (!infop)
return err;
if (put_user(err ? 0 : SIGCHLD, &infop->si_signo) ||
put_user(0, &infop->si_errno) ||
put_user((short)info.cause, &infop->si_code) ||
put_user(info.pid, &infop->si_pid) ||
put_user(info.uid, &infop->si_uid) ||
put_user(info.status, &infop->si_status))
err = -EFAULT;
return err; return err;
} }
@ -1785,33 +1751,27 @@ COMPAT_SYSCALL_DEFINE5(waitid,
struct compat_siginfo __user *, infop, int, options, struct compat_siginfo __user *, infop, int, options,
struct compat_rusage __user *, uru) struct compat_rusage __user *, uru)
{ {
siginfo_t info;
struct rusage ru; struct rusage ru;
long ret; struct waitid_info info = {.status = 0};
mm_segment_t old_fs = get_fs(); long err = kernel_waitid(which, pid, &info, options, uru ? &ru : NULL);
memset(&info, 0, sizeof(info)); if (!err && uru) {
/* kernel_waitid() overwrites everything in ru */
set_fs(KERNEL_DS);
ret = kernel_waitid(which, pid, (siginfo_t __user *)&info, options,
uru ? &ru : NULL);
set_fs(old_fs);
if ((ret < 0) || (info.si_signo == 0))
return ret;
if (uru) {
/* sys_waitid() overwrites everything in ru */
if (COMPAT_USE_64BIT_TIME) if (COMPAT_USE_64BIT_TIME)
ret = copy_to_user(uru, &ru, sizeof(ru)); err = copy_to_user(uru, &ru, sizeof(ru));
else else
ret = put_compat_rusage(&ru, uru); err = put_compat_rusage(&ru, uru);
if (ret) if (err)
return -EFAULT; return -EFAULT;
} }
BUG_ON(info.si_code & __SI_MASK); if (put_user(err ? 0 : SIGCHLD, &infop->si_signo) ||
info.si_code |= __SI_CHLD; put_user(0, &infop->si_errno) ||
return copy_siginfo_to_user32(infop, &info); put_user((short)info.cause, &infop->si_code) ||
put_user(info.pid, &infop->si_pid) ||
put_user(info.uid, &infop->si_uid) ||
put_user(info.status, &infop->si_status))
err = -EFAULT;
return err;
} }
#endif #endif