Author: kib
Date: Tue Oct 27 10:55:34 2009
New Revision: 198508
URL: http://svn.freebsd.org/changeset/base/198508
Log:
Current pselect(3) is implemented in usermode and thus vulnerable to
well-known race condition, which elimination was the reason for the
function appearance in first place. If sigmask supplied as argument to
pselect() enables a signal, the signal might be delivered before thread
called select(2), causing lost wakeup. Reimplement pselect() in kernel,
making change of sigmask and sleep atomic.
Since signal shall be delivered to the usermode, but sigmask restored,
set TDP_OLDMASK and save old mask in td_oldsigmask. The TDP_OLDMASK
should be cleared by ast() in case signal was not gelivered during
syscall execution.
Reviewed by: davidxu
Tested by: pho
MFC after: 1 month
Deleted:
head/lib/libc/gen/pselect.c
Modified:
head/lib/libc/sys/Symbol.map
head/lib/libthr/thread/thr_syscalls.c
head/sys/compat/freebsd32/freebsd32_misc.c
head/sys/compat/freebsd32/syscalls.master
head/sys/kern/subr_trap.c
head/sys/kern/sys_generic.c
head/sys/kern/syscalls.master
head/sys/sys/syscallsubr.h
Modified: head/lib/libc/sys/Symbol.map
==============================================================================
--- head/lib/libc/sys/Symbol.map Tue Oct 27 10:47:58 2009
(r198507)
+++ head/lib/libc/sys/Symbol.map Tue Oct 27 10:55:34 2009
(r198508)
@@ -211,6 +211,7 @@ FBSD_1.0 {
posix_openpt;
preadv;
profil;
+ pselect;
ptrace;
pwritev;
quotactl;
@@ -781,6 +782,8 @@ FBSDprivate_1.0 {
__sys_preadv;
_profil;
__sys_profil;
+ _pselect;
+ __sys_pselect;
_ptrace;
__sys_ptrace;
_pwritev;
Modified: head/lib/libthr/thread/thr_syscalls.c
==============================================================================
--- head/lib/libthr/thread/thr_syscalls.c Tue Oct 27 10:47:58 2009
(r198507)
+++ head/lib/libthr/thread/thr_syscalls.c Tue Oct 27 10:55:34 2009
(r198508)
@@ -104,6 +104,8 @@ extern int __sys_accept(int, struct sock
extern int __sys_connect(int, const struct sockaddr *, socklen_t);
extern int __sys_fsync(int);
extern int __sys_msync(void *, size_t, int);
+extern int __sys_pselect(int, fd_set *, fd_set *, fd_set *,
+ const struct timespec *, const sigset_t *);
extern int __sys_poll(struct pollfd *, unsigned, int);
extern ssize_t __sys_recv(int, void *, size_t, int);
extern ssize_t __sys_recvfrom(int, void *, size_t, int, struct sockaddr *,
socklen_t *);
@@ -394,7 +396,7 @@ ___pselect(int count, fd_set *rfds, fd_s
int ret;
_thr_cancel_enter(curthread);
- ret = __pselect(count, rfds, wfds, efds, timo, mask);
+ ret = __sys_pselect(count, rfds, wfds, efds, timo, mask);
_thr_cancel_leave(curthread);
return (ret);
Modified: head/sys/compat/freebsd32/freebsd32_misc.c
==============================================================================
--- head/sys/compat/freebsd32/freebsd32_misc.c Tue Oct 27 10:47:58 2009
(r198507)
+++ head/sys/compat/freebsd32/freebsd32_misc.c Tue Oct 27 10:55:34 2009
(r198508)
@@ -593,6 +593,41 @@ freebsd32_select(struct thread *td, stru
sizeof(int32_t) * 8));
}
+int
+freebsd32_pselect(struct thread *td, struct freebsd32_pselect_args *uap)
+{
+ struct timespec32 ts32;
+ struct timespec ts;
+ struct timeval tv, *tvp;
+ sigset_t set, *uset;
+ int error;
+
+ if (uap->ts != NULL) {
+ error = copyin(uap->ts, &ts32, sizeof(ts32));
+ if (error != 0)
+ return (error);
+ CP(ts32, ts, tv_sec);
+ CP(ts32, ts, tv_nsec);
+ TIMESPEC_TO_TIMEVAL(&tv, &ts);
+ tvp = &tv;
+ } else
+ tvp = NULL;
+ if (uap->sm != NULL) {
+ error = copyin(uap->sm, &set, sizeof(set));
+ if (error != 0)
+ return (error);
+ uset = &set;
+ } else
+ uset = NULL;
+ /*
+ * XXX big-endian needs to convert the fd_sets too.
+ * XXX Do pointers need PTRIN()?
+ */
+ error = kern_pselect(td, uap->nd, uap->in, uap->ou, uap->ex, tvp,
+ uset, sizeof(int32_t) * 8);
+ return (error);
+}
+
/*
* Copy 'count' items into the destination list pointed to by uap->eventlist.
*/
Modified: head/sys/compat/freebsd32/syscalls.master
==============================================================================
--- head/sys/compat/freebsd32/syscalls.master Tue Oct 27 10:47:58 2009
(r198507)
+++ head/sys/compat/freebsd32/syscalls.master Tue Oct 27 10:55:34 2009
(r198508)
@@ -909,3 +909,7 @@
519 AUE_PDKILL UNIMPL pdkill
520 AUE_PDGETPID UNIMPL pdgetpid
521 AUE_PDWAIT UNIMPL pdwait
+522 AUE_SELECT STD { int freebsd32_pselect(int nd, fd_set *in, \
+ fd_set *ou, fd_set *ex, \
+ const struct timespec32 *ts, \
+ const sigset_t *sm); }
Modified: head/sys/kern/subr_trap.c
==============================================================================
--- head/sys/kern/subr_trap.c Tue Oct 27 10:47:58 2009 (r198507)
+++ head/sys/kern/subr_trap.c Tue Oct 27 10:55:34 2009 (r198508)
@@ -245,6 +245,11 @@ ast(struct trapframe *framep)
PROC_UNLOCK(p);
}
+ if (td->td_pflags & TDP_OLDMASK) {
+ td->td_pflags &= ~TDP_OLDMASK;
+ kern_sigprocmask(td, SIG_SETMASK, &td->td_oldsigmask, NULL, 0);
+ }
+
userret(td, framep);
mtx_assert(&Giant, MA_NOTOWNED);
}
Modified: head/sys/kern/sys_generic.c
==============================================================================
--- head/sys/kern/sys_generic.c Tue Oct 27 10:47:58 2009 (r198507)
+++ head/sys/kern/sys_generic.c Tue Oct 27 10:55:34 2009 (r198508)
@@ -751,6 +751,58 @@ poll_no_poll(int events)
return (events & (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM));
}
+int
+pselect(struct thread *td, struct pselect_args *uap)
+{
+ struct timespec ts;
+ struct timeval tv, *tvp;
+ sigset_t set, *uset;
+ int error;
+
+ if (uap->ts != NULL) {
+ error = copyin(uap->ts, &ts, sizeof(ts));
+ if (error != 0)
+ return (error);
+ TIMESPEC_TO_TIMEVAL(&tv, &ts);
+ tvp = &tv;
+ } else
+ tvp = NULL;
+ if (uap->sm != NULL) {
+ error = copyin(uap->sm, &set, sizeof(set));
+ if (error != 0)
+ return (error);
+ uset = &set;
+ } else
+ uset = NULL;
+ return (kern_pselect(td, uap->nd, uap->in, uap->ou, uap->ex, tvp,
+ uset, NFDBITS));
+}
+
+int
+kern_pselect(struct thread *td, int nd, fd_set *in, fd_set *ou, fd_set *ex,
+ struct timeval *tvp, sigset_t *uset, int abi_nfdbits)
+{
+ int error;
+
+ if (uset != NULL) {
+ error = kern_sigprocmask(td, SIG_SETMASK, uset,
+ &td->td_oldsigmask, 0);
+ if (error != 0)
+ return (error);
+ td->td_pflags |= TDP_OLDMASK;
+ /*
+ * Make sure that ast() is called on return to
+ * usermode and TDP_OLDMASK is cleared, restoring old
+ * sigmask.
+ */
+ thread_lock(td);
+ td->td_flags |= TDF_ASTPENDING;
+ thread_unlock(td);
+ }
+ error = kern_select(td, nd, in, ou, ex, tvp, abi_nfdbits);
+ return (error);
+}
+
#ifndef _SYS_SYSPROTO_H_
struct select_args {
int nd;
@@ -759,9 +811,7 @@ struct select_args {
};
#endif
int
-select(td, uap)
- register struct thread *td;
- register struct select_args *uap;
+select(struct thread *td, struct select_args *uap)
{
struct timeval tv, *tvp;
int error;
Modified: head/sys/kern/syscalls.master
==============================================================================
--- head/sys/kern/syscalls.master Tue Oct 27 10:47:58 2009
(r198507)
+++ head/sys/kern/syscalls.master Tue Oct 27 10:55:34 2009
(r198508)
@@ -919,5 +919,9 @@
519 AUE_PDKILL UNIMPL pdkill
520 AUE_PDGETPID UNIMPL pdgetpid
521 AUE_PDWAIT UNIMPL pdwait
+522 AUE_SELECT STD { int pselect(int nd, fd_set *in, \
+ fd_set *ou, fd_set *ex, \
+ const struct timespec *ts, \
+ const sigset_t *sm); }
; Please copy any additions and changes to the following compatability tables:
; sys/compat/freebsd32/syscalls.master
Modified: head/sys/sys/syscallsubr.h
==============================================================================
--- head/sys/sys/syscallsubr.h Tue Oct 27 10:47:58 2009 (r198507)
+++ head/sys/sys/syscallsubr.h Tue Oct 27 10:55:34 2009 (r198508)
@@ -148,6 +148,8 @@ int kern_pathconf(struct thread *td, cha
int name, u_long flags);
int kern_pipe(struct thread *td, int fildes[2]);
int kern_preadv(struct thread *td, int fd, struct uio *auio, off_t offset);
+int kern_pselect(struct thread *td, int nd, fd_set *in, fd_set *ou,
+ fd_set *ex, struct timeval *tvp, sigset_t *uset, int abi_nfdbits);
int kern_ptrace(struct thread *td, int req, pid_t pid, void *addr,
int data);
int kern_pwritev(struct thread *td, int fd, struct uio *auio, off_t offset);
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