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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>
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Al Viro committed May 21, 2017
1 parent 359566f commit 67d7ddd
Showing 1 changed file with 64 additions and 104 deletions.
168 changes: 64 additions & 104 deletions kernel/exit.c
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Original file line number Diff line number Diff line change
Expand Up @@ -996,12 +996,19 @@ 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 siginfo __user *wo_info;
struct waitid_info *wo_info;
int wo_stat;
struct rusage *wo_rusage;

Expand Down Expand Up @@ -1053,31 +1060,20 @@ 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,
pid_t pid, uid_t uid, int why, int status)
{
struct siginfo __user *infop;
int retval = 0;
struct waitid_info *infop;

if (wo->wo_rusage)
getrusage(p, RUSAGE_BOTH, wo->wo_rusage);

put_task_struct(p);
infop = wo->wo_info;
if (infop) {
if (!retval)
retval = put_user(SIGCHLD, &infop->si_signo);
if (!retval)
retval = put_user(0, &infop->si_errno);
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);
infop->cause = why;
infop->pid = pid;
infop->uid = uid;
infop->status = status;
}
if (!retval)
retval = pid;
return retval;
return pid;
}

/*
Expand All @@ -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)
{
int state, retval, status;
int state, status;
pid_t pid = task_pid_vnr(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))
return 0;
Expand Down Expand Up @@ -1186,36 +1182,22 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)

if (wo->wo_rusage)
getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
retval = 0;
status = (p->signal->flags & SIGNAL_GROUP_EXIT)
? p->signal->group_exit_code : p->exit_code;
wo->wo_stat = status;

infop = wo->wo_info;
if (!retval && infop)
retval = put_user(SIGCHLD, &infop->si_signo);
if (!retval && infop)
retval = put_user(0, &infop->si_errno);
if (!retval && infop) {
int why;

if (infop) {
if ((status & 0x7f) == 0) {
why = CLD_EXITED;
status >>= 8;
infop->cause = CLD_EXITED;
infop->status = status >> 8;
} else {
why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
status &= 0x7f;
infop->cause = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
infop->status = status & 0x7f;
}
retval = put_user((short)why, &infop->si_code);
if (!retval)
retval = put_user(status, &infop->si_status);
infop->pid = pid;
infop->uid = uid;
}
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) {
write_lock_irq(&tasklist_lock);
Expand All @@ -1232,7 +1214,7 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
if (state == EXIT_DEAD)
release_task(p);

return retval;
return pid;
}

static int *task_stopped_code(struct task_struct *p, bool ptrace)
Expand Down Expand Up @@ -1268,8 +1250,8 @@ 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 siginfo __user *infop;
int retval, exit_code, *p_code, why;
struct waitid_info *infop;
int exit_code, *p_code, why;
uid_t uid = 0; /* unneeded, required by compiler */
pid_t pid;

Expand Down Expand Up @@ -1320,28 +1302,19 @@ static int wait_task_stopped(struct wait_opts *wo,

if (wo->wo_rusage)
getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
retval = 0;
wo->wo_stat = (exit_code << 8) | 0x7f;

infop = wo->wo_info;
if (!retval && infop)
retval = put_user(SIGCHLD, &infop->si_signo);
if (!retval && infop)
retval = put_user(0, &infop->si_errno);
if (!retval && infop)
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;
if (infop) {
infop->cause = why;
infop->status = exit_code;
infop->pid = pid;
infop->uid = uid;
}
put_task_struct(p);

BUG_ON(!retval);
return retval;
BUG_ON(!pid);
return pid;
}

/*
Expand Down Expand Up @@ -1618,7 +1591,7 @@ static long do_wait(struct wait_opts *wo)
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)
{
struct wait_opts wo;
Expand Down Expand Up @@ -1660,27 +1633,8 @@ static long kernel_waitid(int which, pid_t upid, struct siginfo __user *infop,
wo.wo_rusage = ru;
ret = do_wait(&wo);

if (ret > 0) {
if (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);
return ret;
Expand All @@ -1690,12 +1644,24 @@ SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
infop, int, options, struct rusage __user *, ru)
{
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 (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
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;
}

Expand Down Expand Up @@ -1785,33 +1751,27 @@ COMPAT_SYSCALL_DEFINE5(waitid,
struct compat_siginfo __user *, infop, int, options,
struct compat_rusage __user *, uru)
{
siginfo_t info;
struct rusage ru;
long ret;
mm_segment_t old_fs = get_fs();

memset(&info, 0, sizeof(info));
struct waitid_info info = {.status = 0};
long err = kernel_waitid(which, pid, &info, options, uru ? &ru : NULL);

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 (!err && uru) {
/* kernel_waitid() overwrites everything in ru */
if (COMPAT_USE_64BIT_TIME)
ret = copy_to_user(uru, &ru, sizeof(ru));
err = copy_to_user(uru, &ru, sizeof(ru));
else
ret = put_compat_rusage(&ru, uru);
if (ret)
err = put_compat_rusage(&ru, uru);
if (err)
return -EFAULT;
}

BUG_ON(info.si_code & __SI_MASK);
info.si_code |= __SI_CHLD;
return copy_siginfo_to_user32(infop, &info);
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;
}
#endif

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