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sigtimedwait: Prevent timeout math overflows.

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Our kern_sigtimedwait() calculates absolute sleep timo value as 'uptime+timeout'.
So, when the user specifies a big timeout value (LONG_MAX), the calculated
timo can be less the the current uptime value.
In that case kern_sigtimedwait() returns EAGAIN instead of EINTR, if
unblocked signal was caught.

While here switch to a high-precision sleep method.

Reviewed by:		mav, kib
In collaboration with:	mav
Differential revision:	https://reviews.freebsd.org/D34981
MFC after:		2 weeks
This commit is contained in:
Dmitry Chagin 2022-04-25 10:23:15 +03:00
parent 6201a50d0d
commit 4a700f3c32
1 changed files with 20 additions and 29 deletions
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49
sys/kern/kern_sig.c
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@ -1258,15 +1258,13 @@ kern_sigtimedwait(struct thread *td, sigset_t waitset, ksiginfo_t *ksi,
struct sigacts *ps;
sigset_t saved_mask, new_block;
struct proc *p;
int error, sig, timo, timevalid = 0;
struct timespec rts, ets, ts;
struct timeval tv;
int error, sig, timevalid = 0;
sbintime_t sbt, precision, tsbt;
struct timespec ts;
bool traced;
p = td->td_proc;
error = 0;
ets.tv_sec = 0;
ets.tv_nsec = 0;
traced = false;
/* Ensure the sigfastblock value is up to date. */
@ -1275,10 +1273,19 @@ kern_sigtimedwait(struct thread *td, sigset_t waitset, ksiginfo_t *ksi,
if (timeout != NULL) {
if (timeout->tv_nsec >= 0 && timeout->tv_nsec < 1000000000) {
timevalid = 1;
getnanouptime(&rts);
timespecadd(&rts, timeout, &ets);
ts = *timeout;
if (ts.tv_sec < INT32_MAX / 2) {
tsbt = tstosbt(ts);
precision = tsbt;
precision >>= tc_precexp;
if (TIMESEL(&sbt, tsbt))
sbt += tc_tick_sbt;
sbt += tsbt;
} else
precision = sbt = 0;
}
}
} else
precision = sbt = 0;
ksiginfo_init(ksi);
/* Some signals can not be waited for. */
SIG_CANTMASK(waitset);
@ -1312,21 +1319,9 @@ kern_sigtimedwait(struct thread *td, sigset_t waitset, ksiginfo_t *ksi,
* POSIX says this must be checked after looking for pending
* signals.
*/
if (timeout != NULL) {
if (!timevalid) {
error = EINVAL;
break;
}
getnanouptime(&rts);
if (timespeccmp(&rts, &ets, >=)) {
error = EAGAIN;
break;
}
timespecsub(&ets, &rts, &ts);
TIMESPEC_TO_TIMEVAL(&tv, &ts);
timo = tvtohz(&tv);
} else {
timo = 0;
if (timeout != NULL && !timevalid) {
error = EINVAL;
break;
}
if (traced) {
@ -1334,17 +1329,13 @@ kern_sigtimedwait(struct thread *td, sigset_t waitset, ksiginfo_t *ksi,
break;
}
error = msleep(&p->p_sigacts, &p->p_mtx, PPAUSE | PCATCH,
"sigwait", timo);
error = msleep_sbt(&p->p_sigacts, &p->p_mtx, PPAUSE | PCATCH,
"sigwait", sbt, precision, C_ABSOLUTE);
/* The syscalls can not be restarted. */
if (error == ERESTART)
error = EINTR;
/* We will calculate timeout by ourself. */
if (timeout != NULL && error == EAGAIN)
error = 0;
/*
* If PTRACE_SCE or PTRACE_SCX were set after
* userspace entered the syscall, return spurious