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Linux epoll: Check both read and write kqueue events existence in EPOLL_CTL_ADD

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Linux epoll EPOLL_CTL_ADD op handler should always check registration
of both EVFILT_READ and EVFILT_WRITE kevents to deceide if supplied
file descriptor fd is already registered with epoll instance.

Reviewed by:	emaste
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D22515
This commit is contained in:
Vladimir Kondratyev 2019-11-24 20:44:14 +00:00
parent 896a4c279d
commit 461120b834
1 changed files with 40 additions and 31 deletions
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71
sys/compat/linux/linux_event.c
View File

@ -98,14 +98,16 @@ __attribute__((packed))
#define LINUX_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event))
static void epoll_fd_install(struct thread *td, int fd, epoll_udata_t udata);
static int epoll_to_kevent(struct thread *td, struct file *epfp,
int fd, struct epoll_event *l_event, int *kev_flags,
struct kevent *kevent, int *nkevents);
static int epoll_to_kevent(struct thread *td, int fd,
struct epoll_event *l_event, struct kevent *kevent,
int *nkevents);
static void kevent_to_epoll(struct kevent *kevent, struct epoll_event *l_event);
static int epoll_kev_copyout(void *arg, struct kevent *kevp, int count);
static int epoll_kev_copyin(void *arg, struct kevent *kevp, int count);
static int epoll_delete_event(struct thread *td, struct file *epfp,
int fd, int filter);
static int epoll_register_kevent(struct thread *td, struct file *epfp,
int fd, int filter, unsigned int flags);
static int epoll_fd_registered(struct thread *td, struct file *epfp,
int fd);
static int epoll_delete_all_events(struct thread *td, struct file *epfp,
int fd);
@ -296,31 +298,31 @@ linux_epoll_create1(struct thread *td, struct linux_epoll_create1_args *args)
/* Structure converting function from epoll to kevent. */
static int
epoll_to_kevent(struct thread *td, struct file *epfp,
int fd, struct epoll_event *l_event, int *kev_flags,
epoll_to_kevent(struct thread *td, int fd, struct epoll_event *l_event,
struct kevent *kevent, int *nkevents)
{
uint32_t levents = l_event->events;
struct linux_pemuldata *pem;
struct proc *p;
unsigned short kev_flags = EV_ADD | EV_ENABLE;
/* flags related to how event is registered */
if ((levents & LINUX_EPOLLONESHOT) != 0)
*kev_flags |= EV_DISPATCH;
kev_flags |= EV_DISPATCH;
if ((levents & LINUX_EPOLLET) != 0)
*kev_flags |= EV_CLEAR;
kev_flags |= EV_CLEAR;
if ((levents & LINUX_EPOLLERR) != 0)
*kev_flags |= EV_ERROR;
kev_flags |= EV_ERROR;
if ((levents & LINUX_EPOLLRDHUP) != 0)
*kev_flags |= EV_EOF;
kev_flags |= EV_EOF;
/* flags related to what event is registered */
if ((levents & LINUX_EPOLL_EVRD) != 0) {
EV_SET(kevent++, fd, EVFILT_READ, *kev_flags, 0, 0, 0);
EV_SET(kevent++, fd, EVFILT_READ, kev_flags, 0, 0, 0);
++(*nkevents);
}
if ((levents & LINUX_EPOLL_EVWR) != 0) {
EV_SET(kevent++, fd, EVFILT_WRITE, *kev_flags, 0, 0, 0);
EV_SET(kevent++, fd, EVFILT_WRITE, kev_flags, 0, 0, 0);
++(*nkevents);
}
@ -451,7 +453,6 @@ linux_epoll_ctl(struct thread *td, struct linux_epoll_ctl_args *args)
epoll_kev_copyin};
struct epoll_event le;
cap_rights_t rights;
int kev_flags;
int nchanges = 0;
int error;
@ -484,9 +485,7 @@ linux_epoll_ctl(struct thread *td, struct linux_epoll_ctl_args *args)
ciargs.changelist = kev;
if (args->op != LINUX_EPOLL_CTL_DEL) {
kev_flags = EV_ADD | EV_ENABLE;
error = epoll_to_kevent(td, epfp, args->fd, &le,
&kev_flags, kev, &nchanges);
error = epoll_to_kevent(td, args->fd, &le, kev, &nchanges);
if (error != 0)
goto leave0;
}
@ -499,19 +498,10 @@ linux_epoll_ctl(struct thread *td, struct linux_epoll_ctl_args *args)
break;
case LINUX_EPOLL_CTL_ADD:
/*
* kqueue_register() return ENOENT if event does not exists
* and the EV_ADD flag is not set. Reset EV_ENABLE flag to
* avoid accidental activation of fired oneshot events.
*/
kev[0].flags &= ~(EV_ADD | EV_ENABLE);
error = kqfd_register(args->epfd, &kev[0], td, M_WAITOK);
if (error != ENOENT) {
if (epoll_fd_registered(td, epfp, args->fd)) {
error = EEXIST;
goto leave0;
}
error = 0;
kev[0].flags |= (EV_ADD | EV_ENABLE);
break;
case LINUX_EPOLL_CTL_DEL:
@ -651,7 +641,8 @@ linux_epoll_pwait(struct thread *td, struct linux_epoll_pwait_args *args)
}
static int
epoll_delete_event(struct thread *td, struct file *epfp, int fd, int filter)
epoll_register_kevent(struct thread *td, struct file *epfp, int fd, int filter,
unsigned int flags)
{
struct epoll_copyin_args ciargs;
struct kevent kev;
@ -660,18 +651,36 @@ epoll_delete_event(struct thread *td, struct file *epfp, int fd, int filter)
epoll_kev_copyin};
ciargs.changelist = &kev;
EV_SET(&kev, fd, filter, EV_DELETE | EV_DISABLE, 0, 0, 0);
EV_SET(&kev, fd, filter, flags, 0, 0, 0);
return (kern_kevent_fp(td, epfp, 1, 0, &k_ops, NULL));
}
static int
epoll_fd_registered(struct thread *td, struct file *epfp, int fd)
{
/*
* Set empty filter flags to avoid accidental modification of already
* registered events. In the case of event re-registration:
* 1. If event does not exists kevent() does nothing and returns ENOENT
* 2. If event does exists, it's enabled/disabled state is preserved
* but fflags, data and udata fields are overwritten. So we can not
* set socket lowats and store user's context pointer in udata.
*/
if (epoll_register_kevent(td, epfp, fd, EVFILT_READ, 0) != ENOENT ||
epoll_register_kevent(td, epfp, fd, EVFILT_WRITE, 0) != ENOENT)
return (1);
return (0);
}
static int
epoll_delete_all_events(struct thread *td, struct file *epfp, int fd)
{
int error1, error2;
error1 = epoll_delete_event(td, epfp, fd, EVFILT_READ);
error2 = epoll_delete_event(td, epfp, fd, EVFILT_WRITE);
error1 = epoll_register_kevent(td, epfp, fd, EVFILT_READ, EV_DELETE);
error2 = epoll_register_kevent(td, epfp, fd, EVFILT_WRITE, EV_DELETE);
/* return 0 if at least one result positive */
return (error1 == 0 ? 0 : error2);