Date: Mon, 25 Apr 2022 07:23:46 GMT From: Dmitry Chagin <dchagin@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 4a700f3c329a - main - sigtimedwait: Prevent timeout math overflows. Message-ID: <202204250723.23P7NkTl065779@gitrepo.freebsd.org>
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The branch main has been updated by dchagin: URL: https://cgit.FreeBSD.org/src/commit/?id=4a700f3c329a48f3a20fd576900820e293c8cad7 commit 4a700f3c329a48f3a20fd576900820e293c8cad7 Author: Dmitry Chagin <dchagin@FreeBSD.org> AuthorDate: 2022-04-25 07:23:15 +0000 Commit: Dmitry Chagin <dchagin@FreeBSD.org> CommitDate: 2022-04-25 07:23:15 +0000 sigtimedwait: Prevent timeout math overflows. 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 --- sys/kern/kern_sig.c | 49 ++++++++++++++++++++----------------------------- 1 file changed, 20 insertions(+), 29 deletions(-) diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c index 55b2957d163b..ce6f517262a4 100644 --- a/sys/kern/kern_sig.c +++ b/sys/kern/kern_sig.c @@ -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
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