Root/fs/pipe.c

1/*
2 * linux/fs/pipe.c
3 *
4 * Copyright (C) 1991, 1992, 1999 Linus Torvalds
5 */
6
7#include <linux/mm.h>
8#include <linux/file.h>
9#include <linux/poll.h>
10#include <linux/slab.h>
11#include <linux/module.h>
12#include <linux/init.h>
13#include <linux/fs.h>
14#include <linux/mount.h>
15#include <linux/pipe_fs_i.h>
16#include <linux/uio.h>
17#include <linux/highmem.h>
18#include <linux/pagemap.h>
19#include <linux/audit.h>
20#include <linux/syscalls.h>
21
22#include <asm/uaccess.h>
23#include <asm/ioctls.h>
24
25/*
26 * We use a start+len construction, which provides full use of the
27 * allocated memory.
28 * -- Florian Coosmann (FGC)
29 *
30 * Reads with count = 0 should always return 0.
31 * -- Julian Bradfield 1999-06-07.
32 *
33 * FIFOs and Pipes now generate SIGIO for both readers and writers.
34 * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
35 *
36 * pipe_read & write cleanup
37 * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
38 */
39
40static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
41{
42    if (pipe->inode)
43        mutex_lock_nested(&pipe->inode->i_mutex, subclass);
44}
45
46void pipe_lock(struct pipe_inode_info *pipe)
47{
48    /*
49     * pipe_lock() nests non-pipe inode locks (for writing to a file)
50     */
51    pipe_lock_nested(pipe, I_MUTEX_PARENT);
52}
53EXPORT_SYMBOL(pipe_lock);
54
55void pipe_unlock(struct pipe_inode_info *pipe)
56{
57    if (pipe->inode)
58        mutex_unlock(&pipe->inode->i_mutex);
59}
60EXPORT_SYMBOL(pipe_unlock);
61
62void pipe_double_lock(struct pipe_inode_info *pipe1,
63              struct pipe_inode_info *pipe2)
64{
65    BUG_ON(pipe1 == pipe2);
66
67    if (pipe1 < pipe2) {
68        pipe_lock_nested(pipe1, I_MUTEX_PARENT);
69        pipe_lock_nested(pipe2, I_MUTEX_CHILD);
70    } else {
71        pipe_lock_nested(pipe2, I_MUTEX_PARENT);
72        pipe_lock_nested(pipe1, I_MUTEX_CHILD);
73    }
74}
75
76/* Drop the inode semaphore and wait for a pipe event, atomically */
77void pipe_wait(struct pipe_inode_info *pipe)
78{
79    DEFINE_WAIT(wait);
80
81    /*
82     * Pipes are system-local resources, so sleeping on them
83     * is considered a noninteractive wait:
84     */
85    prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
86    pipe_unlock(pipe);
87    schedule();
88    finish_wait(&pipe->wait, &wait);
89    pipe_lock(pipe);
90}
91
92static int
93pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len,
94            int atomic)
95{
96    unsigned long copy;
97
98    while (len > 0) {
99        while (!iov->iov_len)
100            iov++;
101        copy = min_t(unsigned long, len, iov->iov_len);
102
103        if (atomic) {
104            if (__copy_from_user_inatomic(to, iov->iov_base, copy))
105                return -EFAULT;
106        } else {
107            if (copy_from_user(to, iov->iov_base, copy))
108                return -EFAULT;
109        }
110        to += copy;
111        len -= copy;
112        iov->iov_base += copy;
113        iov->iov_len -= copy;
114    }
115    return 0;
116}
117
118static int
119pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len,
120              int atomic)
121{
122    unsigned long copy;
123
124    while (len > 0) {
125        while (!iov->iov_len)
126            iov++;
127        copy = min_t(unsigned long, len, iov->iov_len);
128
129        if (atomic) {
130            if (__copy_to_user_inatomic(iov->iov_base, from, copy))
131                return -EFAULT;
132        } else {
133            if (copy_to_user(iov->iov_base, from, copy))
134                return -EFAULT;
135        }
136        from += copy;
137        len -= copy;
138        iov->iov_base += copy;
139        iov->iov_len -= copy;
140    }
141    return 0;
142}
143
144/*
145 * Attempt to pre-fault in the user memory, so we can use atomic copies.
146 * Returns the number of bytes not faulted in.
147 */
148static int iov_fault_in_pages_write(struct iovec *iov, unsigned long len)
149{
150    while (!iov->iov_len)
151        iov++;
152
153    while (len > 0) {
154        unsigned long this_len;
155
156        this_len = min_t(unsigned long, len, iov->iov_len);
157        if (fault_in_pages_writeable(iov->iov_base, this_len))
158            break;
159
160        len -= this_len;
161        iov++;
162    }
163
164    return len;
165}
166
167/*
168 * Pre-fault in the user memory, so we can use atomic copies.
169 */
170static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
171{
172    while (!iov->iov_len)
173        iov++;
174
175    while (len > 0) {
176        unsigned long this_len;
177
178        this_len = min_t(unsigned long, len, iov->iov_len);
179        fault_in_pages_readable(iov->iov_base, this_len);
180        len -= this_len;
181        iov++;
182    }
183}
184
185static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
186                  struct pipe_buffer *buf)
187{
188    struct page *page = buf->page;
189
190    /*
191     * If nobody else uses this page, and we don't already have a
192     * temporary page, let's keep track of it as a one-deep
193     * allocation cache. (Otherwise just release our reference to it)
194     */
195    if (page_count(page) == 1 && !pipe->tmp_page)
196        pipe->tmp_page = page;
197    else
198        page_cache_release(page);
199}
200
201/**
202 * generic_pipe_buf_map - virtually map a pipe buffer
203 * @pipe: the pipe that the buffer belongs to
204 * @buf: the buffer that should be mapped
205 * @atomic: whether to use an atomic map
206 *
207 * Description:
208 * This function returns a kernel virtual address mapping for the
209 * pipe_buffer passed in @buf. If @atomic is set, an atomic map is provided
210 * and the caller has to be careful not to fault before calling
211 * the unmap function.
212 *
213 * Note that this function occupies KM_USER0 if @atomic != 0.
214 */
215void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
216               struct pipe_buffer *buf, int atomic)
217{
218    if (atomic) {
219        buf->flags |= PIPE_BUF_FLAG_ATOMIC;
220        return kmap_atomic(buf->page, KM_USER0);
221    }
222
223    return kmap(buf->page);
224}
225
226/**
227 * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer
228 * @pipe: the pipe that the buffer belongs to
229 * @buf: the buffer that should be unmapped
230 * @map_data: the data that the mapping function returned
231 *
232 * Description:
233 * This function undoes the mapping that ->map() provided.
234 */
235void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
236                struct pipe_buffer *buf, void *map_data)
237{
238    if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
239        buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
240        kunmap_atomic(map_data, KM_USER0);
241    } else
242        kunmap(buf->page);
243}
244
245/**
246 * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
247 * @pipe: the pipe that the buffer belongs to
248 * @buf: the buffer to attempt to steal
249 *
250 * Description:
251 * This function attempts to steal the &struct page attached to
252 * @buf. If successful, this function returns 0 and returns with
253 * the page locked. The caller may then reuse the page for whatever
254 * he wishes; the typical use is insertion into a different file
255 * page cache.
256 */
257int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
258               struct pipe_buffer *buf)
259{
260    struct page *page = buf->page;
261
262    /*
263     * A reference of one is golden, that means that the owner of this
264     * page is the only one holding a reference to it. lock the page
265     * and return OK.
266     */
267    if (page_count(page) == 1) {
268        lock_page(page);
269        return 0;
270    }
271
272    return 1;
273}
274
275/**
276 * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
277 * @pipe: the pipe that the buffer belongs to
278 * @buf: the buffer to get a reference to
279 *
280 * Description:
281 * This function grabs an extra reference to @buf. It's used in
282 * in the tee() system call, when we duplicate the buffers in one
283 * pipe into another.
284 */
285void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
286{
287    page_cache_get(buf->page);
288}
289
290/**
291 * generic_pipe_buf_confirm - verify contents of the pipe buffer
292 * @info: the pipe that the buffer belongs to
293 * @buf: the buffer to confirm
294 *
295 * Description:
296 * This function does nothing, because the generic pipe code uses
297 * pages that are always good when inserted into the pipe.
298 */
299int generic_pipe_buf_confirm(struct pipe_inode_info *info,
300                 struct pipe_buffer *buf)
301{
302    return 0;
303}
304
305/**
306 * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
307 * @pipe: the pipe that the buffer belongs to
308 * @buf: the buffer to put a reference to
309 *
310 * Description:
311 * This function releases a reference to @buf.
312 */
313void generic_pipe_buf_release(struct pipe_inode_info *pipe,
314                  struct pipe_buffer *buf)
315{
316    page_cache_release(buf->page);
317}
318
319static const struct pipe_buf_operations anon_pipe_buf_ops = {
320    .can_merge = 1,
321    .map = generic_pipe_buf_map,
322    .unmap = generic_pipe_buf_unmap,
323    .confirm = generic_pipe_buf_confirm,
324    .release = anon_pipe_buf_release,
325    .steal = generic_pipe_buf_steal,
326    .get = generic_pipe_buf_get,
327};
328
329static ssize_t
330pipe_read(struct kiocb *iocb, const struct iovec *_iov,
331       unsigned long nr_segs, loff_t pos)
332{
333    struct file *filp = iocb->ki_filp;
334    struct inode *inode = filp->f_path.dentry->d_inode;
335    struct pipe_inode_info *pipe;
336    int do_wakeup;
337    ssize_t ret;
338    struct iovec *iov = (struct iovec *)_iov;
339    size_t total_len;
340
341    total_len = iov_length(iov, nr_segs);
342    /* Null read succeeds. */
343    if (unlikely(total_len == 0))
344        return 0;
345
346    do_wakeup = 0;
347    ret = 0;
348    mutex_lock(&inode->i_mutex);
349    pipe = inode->i_pipe;
350    for (;;) {
351        int bufs = pipe->nrbufs;
352        if (bufs) {
353            int curbuf = pipe->curbuf;
354            struct pipe_buffer *buf = pipe->bufs + curbuf;
355            const struct pipe_buf_operations *ops = buf->ops;
356            void *addr;
357            size_t chars = buf->len;
358            int error, atomic;
359
360            if (chars > total_len)
361                chars = total_len;
362
363            error = ops->confirm(pipe, buf);
364            if (error) {
365                if (!ret)
366                    error = ret;
367                break;
368            }
369
370            atomic = !iov_fault_in_pages_write(iov, chars);
371redo:
372            addr = ops->map(pipe, buf, atomic);
373            error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic);
374            ops->unmap(pipe, buf, addr);
375            if (unlikely(error)) {
376                /*
377                 * Just retry with the slow path if we failed.
378                 */
379                if (atomic) {
380                    atomic = 0;
381                    goto redo;
382                }
383                if (!ret)
384                    ret = error;
385                break;
386            }
387            ret += chars;
388            buf->offset += chars;
389            buf->len -= chars;
390            if (!buf->len) {
391                buf->ops = NULL;
392                ops->release(pipe, buf);
393                curbuf = (curbuf + 1) & (PIPE_BUFFERS-1);
394                pipe->curbuf = curbuf;
395                pipe->nrbufs = --bufs;
396                do_wakeup = 1;
397            }
398            total_len -= chars;
399            if (!total_len)
400                break; /* common path: read succeeded */
401        }
402        if (bufs) /* More to do? */
403            continue;
404        if (!pipe->writers)
405            break;
406        if (!pipe->waiting_writers) {
407            /* syscall merging: Usually we must not sleep
408             * if O_NONBLOCK is set, or if we got some data.
409             * But if a writer sleeps in kernel space, then
410             * we can wait for that data without violating POSIX.
411             */
412            if (ret)
413                break;
414            if (filp->f_flags & O_NONBLOCK) {
415                ret = -EAGAIN;
416                break;
417            }
418        }
419        if (signal_pending(current)) {
420            if (!ret)
421                ret = -ERESTARTSYS;
422            break;
423        }
424        if (do_wakeup) {
425            wake_up_interruptible_sync(&pipe->wait);
426             kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
427        }
428        pipe_wait(pipe);
429    }
430    mutex_unlock(&inode->i_mutex);
431
432    /* Signal writers asynchronously that there is more room. */
433    if (do_wakeup) {
434        wake_up_interruptible_sync(&pipe->wait);
435        kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
436    }
437    if (ret > 0)
438        file_accessed(filp);
439    return ret;
440}
441
442static ssize_t
443pipe_write(struct kiocb *iocb, const struct iovec *_iov,
444        unsigned long nr_segs, loff_t ppos)
445{
446    struct file *filp = iocb->ki_filp;
447    struct inode *inode = filp->f_path.dentry->d_inode;
448    struct pipe_inode_info *pipe;
449    ssize_t ret;
450    int do_wakeup;
451    struct iovec *iov = (struct iovec *)_iov;
452    size_t total_len;
453    ssize_t chars;
454
455    total_len = iov_length(iov, nr_segs);
456    /* Null write succeeds. */
457    if (unlikely(total_len == 0))
458        return 0;
459
460    do_wakeup = 0;
461    ret = 0;
462    mutex_lock(&inode->i_mutex);
463    pipe = inode->i_pipe;
464
465    if (!pipe->readers) {
466        send_sig(SIGPIPE, current, 0);
467        ret = -EPIPE;
468        goto out;
469    }
470
471    /* We try to merge small writes */
472    chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
473    if (pipe->nrbufs && chars != 0) {
474        int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
475                            (PIPE_BUFFERS-1);
476        struct pipe_buffer *buf = pipe->bufs + lastbuf;
477        const struct pipe_buf_operations *ops = buf->ops;
478        int offset = buf->offset + buf->len;
479
480        if (ops->can_merge && offset + chars <= PAGE_SIZE) {
481            int error, atomic = 1;
482            void *addr;
483
484            error = ops->confirm(pipe, buf);
485            if (error)
486                goto out;
487
488            iov_fault_in_pages_read(iov, chars);
489redo1:
490            addr = ops->map(pipe, buf, atomic);
491            error = pipe_iov_copy_from_user(offset + addr, iov,
492                            chars, atomic);
493            ops->unmap(pipe, buf, addr);
494            ret = error;
495            do_wakeup = 1;
496            if (error) {
497                if (atomic) {
498                    atomic = 0;
499                    goto redo1;
500                }
501                goto out;
502            }
503            buf->len += chars;
504            total_len -= chars;
505            ret = chars;
506            if (!total_len)
507                goto out;
508        }
509    }
510
511    for (;;) {
512        int bufs;
513
514        if (!pipe->readers) {
515            send_sig(SIGPIPE, current, 0);
516            if (!ret)
517                ret = -EPIPE;
518            break;
519        }
520        bufs = pipe->nrbufs;
521        if (bufs < PIPE_BUFFERS) {
522            int newbuf = (pipe->curbuf + bufs) & (PIPE_BUFFERS-1);
523            struct pipe_buffer *buf = pipe->bufs + newbuf;
524            struct page *page = pipe->tmp_page;
525            char *src;
526            int error, atomic = 1;
527
528            if (!page) {
529                page = alloc_page(GFP_HIGHUSER);
530                if (unlikely(!page)) {
531                    ret = ret ? : -ENOMEM;
532                    break;
533                }
534                pipe->tmp_page = page;
535            }
536            /* Always wake up, even if the copy fails. Otherwise
537             * we lock up (O_NONBLOCK-)readers that sleep due to
538             * syscall merging.
539             * FIXME! Is this really true?
540             */
541            do_wakeup = 1;
542            chars = PAGE_SIZE;
543            if (chars > total_len)
544                chars = total_len;
545
546            iov_fault_in_pages_read(iov, chars);
547redo2:
548            if (atomic)
549                src = kmap_atomic(page, KM_USER0);
550            else
551                src = kmap(page);
552
553            error = pipe_iov_copy_from_user(src, iov, chars,
554                            atomic);
555            if (atomic)
556                kunmap_atomic(src, KM_USER0);
557            else
558                kunmap(page);
559
560            if (unlikely(error)) {
561                if (atomic) {
562                    atomic = 0;
563                    goto redo2;
564                }
565                if (!ret)
566                    ret = error;
567                break;
568            }
569            ret += chars;
570
571            /* Insert it into the buffer array */
572            buf->page = page;
573            buf->ops = &anon_pipe_buf_ops;
574            buf->offset = 0;
575            buf->len = chars;
576            pipe->nrbufs = ++bufs;
577            pipe->tmp_page = NULL;
578
579            total_len -= chars;
580            if (!total_len)
581                break;
582        }
583        if (bufs < PIPE_BUFFERS)
584            continue;
585        if (filp->f_flags & O_NONBLOCK) {
586            if (!ret)
587                ret = -EAGAIN;
588            break;
589        }
590        if (signal_pending(current)) {
591            if (!ret)
592                ret = -ERESTARTSYS;
593            break;
594        }
595        if (do_wakeup) {
596            wake_up_interruptible_sync(&pipe->wait);
597            kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
598            do_wakeup = 0;
599        }
600        pipe->waiting_writers++;
601        pipe_wait(pipe);
602        pipe->waiting_writers--;
603    }
604out:
605    mutex_unlock(&inode->i_mutex);
606    if (do_wakeup) {
607        wake_up_interruptible_sync(&pipe->wait);
608        kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
609    }
610    if (ret > 0)
611        file_update_time(filp);
612    return ret;
613}
614
615static ssize_t
616bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
617{
618    return -EBADF;
619}
620
621static ssize_t
622bad_pipe_w(struct file *filp, const char __user *buf, size_t count,
623       loff_t *ppos)
624{
625    return -EBADF;
626}
627
628static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
629{
630    struct inode *inode = filp->f_path.dentry->d_inode;
631    struct pipe_inode_info *pipe;
632    int count, buf, nrbufs;
633
634    switch (cmd) {
635        case FIONREAD:
636            mutex_lock(&inode->i_mutex);
637            pipe = inode->i_pipe;
638            count = 0;
639            buf = pipe->curbuf;
640            nrbufs = pipe->nrbufs;
641            while (--nrbufs >= 0) {
642                count += pipe->bufs[buf].len;
643                buf = (buf+1) & (PIPE_BUFFERS-1);
644            }
645            mutex_unlock(&inode->i_mutex);
646
647            return put_user(count, (int __user *)arg);
648        default:
649            return -EINVAL;
650    }
651}
652
653/* No kernel lock held - fine */
654static unsigned int
655pipe_poll(struct file *filp, poll_table *wait)
656{
657    unsigned int mask;
658    struct inode *inode = filp->f_path.dentry->d_inode;
659    struct pipe_inode_info *pipe = inode->i_pipe;
660    int nrbufs;
661
662    poll_wait(filp, &pipe->wait, wait);
663
664    /* Reading only -- no need for acquiring the semaphore. */
665    nrbufs = pipe->nrbufs;
666    mask = 0;
667    if (filp->f_mode & FMODE_READ) {
668        mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
669        if (!pipe->writers && filp->f_version != pipe->w_counter)
670            mask |= POLLHUP;
671    }
672
673    if (filp->f_mode & FMODE_WRITE) {
674        mask |= (nrbufs < PIPE_BUFFERS) ? POLLOUT | POLLWRNORM : 0;
675        /*
676         * Most Unices do not set POLLERR for FIFOs but on Linux they
677         * behave exactly like pipes for poll().
678         */
679        if (!pipe->readers)
680            mask |= POLLERR;
681    }
682
683    return mask;
684}
685
686static int
687pipe_release(struct inode *inode, int decr, int decw)
688{
689    struct pipe_inode_info *pipe;
690
691    mutex_lock(&inode->i_mutex);
692    pipe = inode->i_pipe;
693    pipe->readers -= decr;
694    pipe->writers -= decw;
695
696    if (!pipe->readers && !pipe->writers) {
697        free_pipe_info(inode);
698    } else {
699        wake_up_interruptible_sync(&pipe->wait);
700        kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
701        kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
702    }
703    mutex_unlock(&inode->i_mutex);
704
705    return 0;
706}
707
708static int
709pipe_read_fasync(int fd, struct file *filp, int on)
710{
711    struct inode *inode = filp->f_path.dentry->d_inode;
712    int retval;
713
714    mutex_lock(&inode->i_mutex);
715    retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_readers);
716    mutex_unlock(&inode->i_mutex);
717
718    return retval;
719}
720
721
722static int
723pipe_write_fasync(int fd, struct file *filp, int on)
724{
725    struct inode *inode = filp->f_path.dentry->d_inode;
726    int retval;
727
728    mutex_lock(&inode->i_mutex);
729    retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_writers);
730    mutex_unlock(&inode->i_mutex);
731
732    return retval;
733}
734
735
736static int
737pipe_rdwr_fasync(int fd, struct file *filp, int on)
738{
739    struct inode *inode = filp->f_path.dentry->d_inode;
740    struct pipe_inode_info *pipe = inode->i_pipe;
741    int retval;
742
743    mutex_lock(&inode->i_mutex);
744    retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
745    if (retval >= 0) {
746        retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
747        if (retval < 0) /* this can happen only if on == T */
748            fasync_helper(-1, filp, 0, &pipe->fasync_readers);
749    }
750    mutex_unlock(&inode->i_mutex);
751    return retval;
752}
753
754
755static int
756pipe_read_release(struct inode *inode, struct file *filp)
757{
758    return pipe_release(inode, 1, 0);
759}
760
761static int
762pipe_write_release(struct inode *inode, struct file *filp)
763{
764    return pipe_release(inode, 0, 1);
765}
766
767static int
768pipe_rdwr_release(struct inode *inode, struct file *filp)
769{
770    int decr, decw;
771
772    decr = (filp->f_mode & FMODE_READ) != 0;
773    decw = (filp->f_mode & FMODE_WRITE) != 0;
774    return pipe_release(inode, decr, decw);
775}
776
777static int
778pipe_read_open(struct inode *inode, struct file *filp)
779{
780    int ret = -ENOENT;
781
782    mutex_lock(&inode->i_mutex);
783
784    if (inode->i_pipe) {
785        ret = 0;
786        inode->i_pipe->readers++;
787    }
788
789    mutex_unlock(&inode->i_mutex);
790
791    return ret;
792}
793
794static int
795pipe_write_open(struct inode *inode, struct file *filp)
796{
797    int ret = -ENOENT;
798
799    mutex_lock(&inode->i_mutex);
800
801    if (inode->i_pipe) {
802        ret = 0;
803        inode->i_pipe->writers++;
804    }
805
806    mutex_unlock(&inode->i_mutex);
807
808    return ret;
809}
810
811static int
812pipe_rdwr_open(struct inode *inode, struct file *filp)
813{
814    int ret = -ENOENT;
815
816    mutex_lock(&inode->i_mutex);
817
818    if (inode->i_pipe) {
819        ret = 0;
820        if (filp->f_mode & FMODE_READ)
821            inode->i_pipe->readers++;
822        if (filp->f_mode & FMODE_WRITE)
823            inode->i_pipe->writers++;
824    }
825
826    mutex_unlock(&inode->i_mutex);
827
828    return ret;
829}
830
831/*
832 * The file_operations structs are not static because they
833 * are also used in linux/fs/fifo.c to do operations on FIFOs.
834 *
835 * Pipes reuse fifos' file_operations structs.
836 */
837const struct file_operations read_pipefifo_fops = {
838    .llseek = no_llseek,
839    .read = do_sync_read,
840    .aio_read = pipe_read,
841    .write = bad_pipe_w,
842    .poll = pipe_poll,
843    .unlocked_ioctl = pipe_ioctl,
844    .open = pipe_read_open,
845    .release = pipe_read_release,
846    .fasync = pipe_read_fasync,
847};
848
849const struct file_operations write_pipefifo_fops = {
850    .llseek = no_llseek,
851    .read = bad_pipe_r,
852    .write = do_sync_write,
853    .aio_write = pipe_write,
854    .poll = pipe_poll,
855    .unlocked_ioctl = pipe_ioctl,
856    .open = pipe_write_open,
857    .release = pipe_write_release,
858    .fasync = pipe_write_fasync,
859};
860
861const struct file_operations rdwr_pipefifo_fops = {
862    .llseek = no_llseek,
863    .read = do_sync_read,
864    .aio_read = pipe_read,
865    .write = do_sync_write,
866    .aio_write = pipe_write,
867    .poll = pipe_poll,
868    .unlocked_ioctl = pipe_ioctl,
869    .open = pipe_rdwr_open,
870    .release = pipe_rdwr_release,
871    .fasync = pipe_rdwr_fasync,
872};
873
874struct pipe_inode_info * alloc_pipe_info(struct inode *inode)
875{
876    struct pipe_inode_info *pipe;
877
878    pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
879    if (pipe) {
880        init_waitqueue_head(&pipe->wait);
881        pipe->r_counter = pipe->w_counter = 1;
882        pipe->inode = inode;
883    }
884
885    return pipe;
886}
887
888void __free_pipe_info(struct pipe_inode_info *pipe)
889{
890    int i;
891
892    for (i = 0; i < PIPE_BUFFERS; i++) {
893        struct pipe_buffer *buf = pipe->bufs + i;
894        if (buf->ops)
895            buf->ops->release(pipe, buf);
896    }
897    if (pipe->tmp_page)
898        __free_page(pipe->tmp_page);
899    kfree(pipe);
900}
901
902void free_pipe_info(struct inode *inode)
903{
904    __free_pipe_info(inode->i_pipe);
905    inode->i_pipe = NULL;
906}
907
908static struct vfsmount *pipe_mnt __read_mostly;
909
910/*
911 * pipefs_dname() is called from d_path().
912 */
913static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
914{
915    return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
916                dentry->d_inode->i_ino);
917}
918
919static const struct dentry_operations pipefs_dentry_operations = {
920    .d_dname = pipefs_dname,
921};
922
923static struct inode * get_pipe_inode(void)
924{
925    struct inode *inode = new_inode(pipe_mnt->mnt_sb);
926    struct pipe_inode_info *pipe;
927
928    if (!inode)
929        goto fail_inode;
930
931    pipe = alloc_pipe_info(inode);
932    if (!pipe)
933        goto fail_iput;
934    inode->i_pipe = pipe;
935
936    pipe->readers = pipe->writers = 1;
937    inode->i_fop = &rdwr_pipefifo_fops;
938
939    /*
940     * Mark the inode dirty from the very beginning,
941     * that way it will never be moved to the dirty
942     * list because "mark_inode_dirty()" will think
943     * that it already _is_ on the dirty list.
944     */
945    inode->i_state = I_DIRTY;
946    inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
947    inode->i_uid = current_fsuid();
948    inode->i_gid = current_fsgid();
949    inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
950
951    return inode;
952
953fail_iput:
954    iput(inode);
955
956fail_inode:
957    return NULL;
958}
959
960struct file *create_write_pipe(int flags)
961{
962    int err;
963    struct inode *inode;
964    struct file *f;
965    struct path path;
966    struct qstr name = { .name = "" };
967
968    err = -ENFILE;
969    inode = get_pipe_inode();
970    if (!inode)
971        goto err;
972
973    err = -ENOMEM;
974    path.dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &name);
975    if (!path.dentry)
976        goto err_inode;
977    path.mnt = mntget(pipe_mnt);
978
979    path.dentry->d_op = &pipefs_dentry_operations;
980    d_instantiate(path.dentry, inode);
981
982    err = -ENFILE;
983    f = alloc_file(&path, FMODE_WRITE, &write_pipefifo_fops);
984    if (!f)
985        goto err_dentry;
986    f->f_mapping = inode->i_mapping;
987
988    f->f_flags = O_WRONLY | (flags & O_NONBLOCK);
989    f->f_version = 0;
990
991    return f;
992
993 err_dentry:
994    free_pipe_info(inode);
995    path_put(&path);
996    return ERR_PTR(err);
997
998 err_inode:
999    free_pipe_info(inode);
1000    iput(inode);
1001 err:
1002    return ERR_PTR(err);
1003}
1004
1005void free_write_pipe(struct file *f)
1006{
1007    free_pipe_info(f->f_dentry->d_inode);
1008    path_put(&f->f_path);
1009    put_filp(f);
1010}
1011
1012struct file *create_read_pipe(struct file *wrf, int flags)
1013{
1014    /* Grab pipe from the writer */
1015    struct file *f = alloc_file(&wrf->f_path, FMODE_READ,
1016                    &read_pipefifo_fops);
1017    if (!f)
1018        return ERR_PTR(-ENFILE);
1019
1020    path_get(&wrf->f_path);
1021    f->f_flags = O_RDONLY | (flags & O_NONBLOCK);
1022
1023    return f;
1024}
1025
1026int do_pipe_flags(int *fd, int flags)
1027{
1028    struct file *fw, *fr;
1029    int error;
1030    int fdw, fdr;
1031
1032    if (flags & ~(O_CLOEXEC | O_NONBLOCK))
1033        return -EINVAL;
1034
1035    fw = create_write_pipe(flags);
1036    if (IS_ERR(fw))
1037        return PTR_ERR(fw);
1038    fr = create_read_pipe(fw, flags);
1039    error = PTR_ERR(fr);
1040    if (IS_ERR(fr))
1041        goto err_write_pipe;
1042
1043    error = get_unused_fd_flags(flags);
1044    if (error < 0)
1045        goto err_read_pipe;
1046    fdr = error;
1047
1048    error = get_unused_fd_flags(flags);
1049    if (error < 0)
1050        goto err_fdr;
1051    fdw = error;
1052
1053    audit_fd_pair(fdr, fdw);
1054    fd_install(fdr, fr);
1055    fd_install(fdw, fw);
1056    fd[0] = fdr;
1057    fd[1] = fdw;
1058
1059    return 0;
1060
1061 err_fdr:
1062    put_unused_fd(fdr);
1063 err_read_pipe:
1064    path_put(&fr->f_path);
1065    put_filp(fr);
1066 err_write_pipe:
1067    free_write_pipe(fw);
1068    return error;
1069}
1070
1071/*
1072 * sys_pipe() is the normal C calling standard for creating
1073 * a pipe. It's not the way Unix traditionally does this, though.
1074 */
1075SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1076{
1077    int fd[2];
1078    int error;
1079
1080    error = do_pipe_flags(fd, flags);
1081    if (!error) {
1082        if (copy_to_user(fildes, fd, sizeof(fd))) {
1083            sys_close(fd[0]);
1084            sys_close(fd[1]);
1085            error = -EFAULT;
1086        }
1087    }
1088    return error;
1089}
1090
1091SYSCALL_DEFINE1(pipe, int __user *, fildes)
1092{
1093    return sys_pipe2(fildes, 0);
1094}
1095
1096/*
1097 * pipefs should _never_ be mounted by userland - too much of security hassle,
1098 * no real gain from having the whole whorehouse mounted. So we don't need
1099 * any operations on the root directory. However, we need a non-trivial
1100 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1101 */
1102static int pipefs_get_sb(struct file_system_type *fs_type,
1103             int flags, const char *dev_name, void *data,
1104             struct vfsmount *mnt)
1105{
1106    return get_sb_pseudo(fs_type, "pipe:", NULL, PIPEFS_MAGIC, mnt);
1107}
1108
1109static struct file_system_type pipe_fs_type = {
1110    .name = "pipefs",
1111    .get_sb = pipefs_get_sb,
1112    .kill_sb = kill_anon_super,
1113};
1114
1115static int __init init_pipe_fs(void)
1116{
1117    int err = register_filesystem(&pipe_fs_type);
1118
1119    if (!err) {
1120        pipe_mnt = kern_mount(&pipe_fs_type);
1121        if (IS_ERR(pipe_mnt)) {
1122            err = PTR_ERR(pipe_mnt);
1123            unregister_filesystem(&pipe_fs_type);
1124        }
1125    }
1126    return err;
1127}
1128
1129static void __exit exit_pipe_fs(void)
1130{
1131    unregister_filesystem(&pipe_fs_type);
1132    mntput(pipe_mnt);
1133}
1134
1135fs_initcall(init_pipe_fs);
1136module_exit(exit_pipe_fs);
1137

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