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- // SPDX-License-Identifier: GPL-2.0
- /*
- * linux/fs/file.c
- *
- * Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
- *
- * Manage the dynamic fd arrays in the process files_struct.
- */
- #include <linux/syscalls.h>
- #include <linux/export.h>
- #include <linux/fs.h>
- #include <linux/kernel.h>
- #include <linux/mm.h>
- #include <linux/sched/signal.h>
- #include <linux/slab.h>
- #include <linux/file.h>
- #include <linux/fdtable.h>
- #include <linux/bitops.h>
- #include <linux/spinlock.h>
- #include <linux/rcupdate.h>
- #include <linux/close_range.h>
- #include <net/sock.h>
- unsigned int sysctl_nr_open __read_mostly = 1024*1024;
- unsigned int sysctl_nr_open_min = BITS_PER_LONG;
- /* our min() is unusable in constant expressions ;-/ */
- #define __const_min(x, y) ((x) < (y) ? (x) : (y))
- unsigned int sysctl_nr_open_max =
- __const_min(INT_MAX, ~(size_t)0/sizeof(void *)) & -BITS_PER_LONG;
- static void __free_fdtable(struct fdtable *fdt)
- {
- kvfree(fdt->fd);
- kvfree(fdt->open_fds);
- kfree(fdt);
- }
- static void free_fdtable_rcu(struct rcu_head *rcu)
- {
- __free_fdtable(container_of(rcu, struct fdtable, rcu));
- }
- #define BITBIT_NR(nr) BITS_TO_LONGS(BITS_TO_LONGS(nr))
- #define BITBIT_SIZE(nr) (BITBIT_NR(nr) * sizeof(long))
- /*
- * Copy 'count' fd bits from the old table to the new table and clear the extra
- * space if any. This does not copy the file pointers. Called with the files
- * spinlock held for write.
- */
- static void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
- unsigned int count)
- {
- unsigned int cpy, set;
- cpy = count / BITS_PER_BYTE;
- set = (nfdt->max_fds - count) / BITS_PER_BYTE;
- memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
- memset((char *)nfdt->open_fds + cpy, 0, set);
- memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
- memset((char *)nfdt->close_on_exec + cpy, 0, set);
- cpy = BITBIT_SIZE(count);
- set = BITBIT_SIZE(nfdt->max_fds) - cpy;
- memcpy(nfdt->full_fds_bits, ofdt->full_fds_bits, cpy);
- memset((char *)nfdt->full_fds_bits + cpy, 0, set);
- }
- /*
- * Copy all file descriptors from the old table to the new, expanded table and
- * clear the extra space. Called with the files spinlock held for write.
- */
- static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
- {
- size_t cpy, set;
- BUG_ON(nfdt->max_fds < ofdt->max_fds);
- cpy = ofdt->max_fds * sizeof(struct file *);
- set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
- memcpy(nfdt->fd, ofdt->fd, cpy);
- memset((char *)nfdt->fd + cpy, 0, set);
- copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);
- }
- /*
- * Note how the fdtable bitmap allocations very much have to be a multiple of
- * BITS_PER_LONG. This is not only because we walk those things in chunks of
- * 'unsigned long' in some places, but simply because that is how the Linux
- * kernel bitmaps are defined to work: they are not "bits in an array of bytes",
- * they are very much "bits in an array of unsigned long".
- *
- * The ALIGN(nr, BITS_PER_LONG) here is for clarity: since we just multiplied
- * by that "1024/sizeof(ptr)" before, we already know there are sufficient
- * clear low bits. Clang seems to realize that, gcc ends up being confused.
- *
- * On a 128-bit machine, the ALIGN() would actually matter. In the meantime,
- * let's consider it documentation (and maybe a test-case for gcc to improve
- * its code generation ;)
- */
- static struct fdtable * alloc_fdtable(unsigned int nr)
- {
- struct fdtable *fdt;
- void *data;
- /*
- * Figure out how many fds we actually want to support in this fdtable.
- * Allocation steps are keyed to the size of the fdarray, since it
- * grows far faster than any of the other dynamic data. We try to fit
- * the fdarray into comfortable page-tuned chunks: starting at 1024B
- * and growing in powers of two from there on.
- */
- nr /= (1024 / sizeof(struct file *));
- nr = roundup_pow_of_two(nr + 1);
- nr *= (1024 / sizeof(struct file *));
- nr = ALIGN(nr, BITS_PER_LONG);
- /*
- * Note that this can drive nr *below* what we had passed if sysctl_nr_open
- * had been set lower between the check in expand_files() and here. Deal
- * with that in caller, it's cheaper that way.
- *
- * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
- * bitmaps handling below becomes unpleasant, to put it mildly...
- */
- if (unlikely(nr > sysctl_nr_open))
- nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
- fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL_ACCOUNT);
- if (!fdt)
- goto out;
- fdt->max_fds = nr;
- data = kvmalloc_array(nr, sizeof(struct file *), GFP_KERNEL_ACCOUNT);
- if (!data)
- goto out_fdt;
- fdt->fd = data;
- data = kvmalloc(max_t(size_t,
- 2 * nr / BITS_PER_BYTE + BITBIT_SIZE(nr), L1_CACHE_BYTES),
- GFP_KERNEL_ACCOUNT);
- if (!data)
- goto out_arr;
- fdt->open_fds = data;
- data += nr / BITS_PER_BYTE;
- fdt->close_on_exec = data;
- data += nr / BITS_PER_BYTE;
- fdt->full_fds_bits = data;
- return fdt;
- out_arr:
- kvfree(fdt->fd);
- out_fdt:
- kfree(fdt);
- out:
- return NULL;
- }
- /*
- * Expand the file descriptor table.
- * This function will allocate a new fdtable and both fd array and fdset, of
- * the given size.
- * Return <0 error code on error; 1 on successful completion.
- * The files->file_lock should be held on entry, and will be held on exit.
- */
- static int expand_fdtable(struct files_struct *files, unsigned int nr)
- __releases(files->file_lock)
- __acquires(files->file_lock)
- {
- struct fdtable *new_fdt, *cur_fdt;
- spin_unlock(&files->file_lock);
- new_fdt = alloc_fdtable(nr);
- /* make sure all __fd_install() have seen resize_in_progress
- * or have finished their rcu_read_lock_sched() section.
- */
- if (atomic_read(&files->count) > 1)
- synchronize_rcu();
- spin_lock(&files->file_lock);
- if (!new_fdt)
- return -ENOMEM;
- /*
- * extremely unlikely race - sysctl_nr_open decreased between the check in
- * caller and alloc_fdtable(). Cheaper to catch it here...
- */
- if (unlikely(new_fdt->max_fds <= nr)) {
- __free_fdtable(new_fdt);
- return -EMFILE;
- }
- cur_fdt = files_fdtable(files);
- BUG_ON(nr < cur_fdt->max_fds);
- copy_fdtable(new_fdt, cur_fdt);
- rcu_assign_pointer(files->fdt, new_fdt);
- if (cur_fdt != &files->fdtab)
- call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
- /* coupled with smp_rmb() in __fd_install() */
- smp_wmb();
- return 1;
- }
- /*
- * Expand files.
- * This function will expand the file structures, if the requested size exceeds
- * the current capacity and there is room for expansion.
- * Return <0 error code on error; 0 when nothing done; 1 when files were
- * expanded and execution may have blocked.
- * The files->file_lock should be held on entry, and will be held on exit.
- */
- static int expand_files(struct files_struct *files, unsigned int nr)
- __releases(files->file_lock)
- __acquires(files->file_lock)
- {
- struct fdtable *fdt;
- int expanded = 0;
- repeat:
- fdt = files_fdtable(files);
- /* Do we need to expand? */
- if (nr < fdt->max_fds)
- return expanded;
- /* Can we expand? */
- if (nr >= sysctl_nr_open)
- return -EMFILE;
- if (unlikely(files->resize_in_progress)) {
- spin_unlock(&files->file_lock);
- expanded = 1;
- wait_event(files->resize_wait, !files->resize_in_progress);
- spin_lock(&files->file_lock);
- goto repeat;
- }
- /* All good, so we try */
- files->resize_in_progress = true;
- expanded = expand_fdtable(files, nr);
- files->resize_in_progress = false;
- wake_up_all(&files->resize_wait);
- return expanded;
- }
- static inline void __set_close_on_exec(unsigned int fd, struct fdtable *fdt)
- {
- __set_bit(fd, fdt->close_on_exec);
- }
- static inline void __clear_close_on_exec(unsigned int fd, struct fdtable *fdt)
- {
- if (test_bit(fd, fdt->close_on_exec))
- __clear_bit(fd, fdt->close_on_exec);
- }
- static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt)
- {
- __set_bit(fd, fdt->open_fds);
- fd /= BITS_PER_LONG;
- if (!~fdt->open_fds[fd])
- __set_bit(fd, fdt->full_fds_bits);
- }
- static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt)
- {
- __clear_bit(fd, fdt->open_fds);
- __clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits);
- }
- static unsigned int count_open_files(struct fdtable *fdt)
- {
- unsigned int size = fdt->max_fds;
- unsigned int i;
- /* Find the last open fd */
- for (i = size / BITS_PER_LONG; i > 0; ) {
- if (fdt->open_fds[--i])
- break;
- }
- i = (i + 1) * BITS_PER_LONG;
- return i;
- }
- /*
- * Note that a sane fdtable size always has to be a multiple of
- * BITS_PER_LONG, since we have bitmaps that are sized by this.
- *
- * 'max_fds' will normally already be properly aligned, but it
- * turns out that in the close_range() -> __close_range() ->
- * unshare_fd() -> dup_fd() -> sane_fdtable_size() we can end
- * up having a 'max_fds' value that isn't already aligned.
- *
- * Rather than make close_range() have to worry about this,
- * just make that BITS_PER_LONG alignment be part of a sane
- * fdtable size. Becuase that's really what it is.
- */
- static unsigned int sane_fdtable_size(struct fdtable *fdt, unsigned int max_fds)
- {
- unsigned int count;
- count = count_open_files(fdt);
- if (max_fds < NR_OPEN_DEFAULT)
- max_fds = NR_OPEN_DEFAULT;
- return ALIGN(min(count, max_fds), BITS_PER_LONG);
- }
- /*
- * Allocate a new files structure and copy contents from the
- * passed in files structure.
- * errorp will be valid only when the returned files_struct is NULL.
- */
- struct files_struct *dup_fd(struct files_struct *oldf, unsigned int max_fds, int *errorp)
- {
- struct files_struct *newf;
- struct file **old_fds, **new_fds;
- unsigned int open_files, i;
- struct fdtable *old_fdt, *new_fdt;
- *errorp = -ENOMEM;
- newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
- if (!newf)
- goto out;
- atomic_set(&newf->count, 1);
- spin_lock_init(&newf->file_lock);
- newf->resize_in_progress = false;
- init_waitqueue_head(&newf->resize_wait);
- newf->next_fd = 0;
- new_fdt = &newf->fdtab;
- new_fdt->max_fds = NR_OPEN_DEFAULT;
- new_fdt->close_on_exec = newf->close_on_exec_init;
- new_fdt->open_fds = newf->open_fds_init;
- new_fdt->full_fds_bits = newf->full_fds_bits_init;
- new_fdt->fd = &newf->fd_array[0];
- spin_lock(&oldf->file_lock);
- old_fdt = files_fdtable(oldf);
- open_files = sane_fdtable_size(old_fdt, max_fds);
- /*
- * Check whether we need to allocate a larger fd array and fd set.
- */
- while (unlikely(open_files > new_fdt->max_fds)) {
- spin_unlock(&oldf->file_lock);
- if (new_fdt != &newf->fdtab)
- __free_fdtable(new_fdt);
- new_fdt = alloc_fdtable(open_files - 1);
- if (!new_fdt) {
- *errorp = -ENOMEM;
- goto out_release;
- }
- /* beyond sysctl_nr_open; nothing to do */
- if (unlikely(new_fdt->max_fds < open_files)) {
- __free_fdtable(new_fdt);
- *errorp = -EMFILE;
- goto out_release;
- }
- /*
- * Reacquire the oldf lock and a pointer to its fd table
- * who knows it may have a new bigger fd table. We need
- * the latest pointer.
- */
- spin_lock(&oldf->file_lock);
- old_fdt = files_fdtable(oldf);
- open_files = sane_fdtable_size(old_fdt, max_fds);
- }
- copy_fd_bitmaps(new_fdt, old_fdt, open_files);
- old_fds = old_fdt->fd;
- new_fds = new_fdt->fd;
- for (i = open_files; i != 0; i--) {
- struct file *f = *old_fds++;
- if (f) {
- get_file(f);
- } else {
- /*
- * The fd may be claimed in the fd bitmap but not yet
- * instantiated in the files array if a sibling thread
- * is partway through open(). So make sure that this
- * fd is available to the new process.
- */
- __clear_open_fd(open_files - i, new_fdt);
- }
- rcu_assign_pointer(*new_fds++, f);
- }
- spin_unlock(&oldf->file_lock);
- /* clear the remainder */
- memset(new_fds, 0, (new_fdt->max_fds - open_files) * sizeof(struct file *));
- rcu_assign_pointer(newf->fdt, new_fdt);
- return newf;
- out_release:
- kmem_cache_free(files_cachep, newf);
- out:
- return NULL;
- }
- static struct fdtable *close_files(struct files_struct * files)
- {
- /*
- * It is safe to dereference the fd table without RCU or
- * ->file_lock because this is the last reference to the
- * files structure.
- */
- struct fdtable *fdt = rcu_dereference_raw(files->fdt);
- unsigned int i, j = 0;
- for (;;) {
- unsigned long set;
- i = j * BITS_PER_LONG;
- if (i >= fdt->max_fds)
- break;
- set = fdt->open_fds[j++];
- while (set) {
- if (set & 1) {
- struct file * file = xchg(&fdt->fd[i], NULL);
- if (file) {
- filp_close(file, files);
- cond_resched();
- }
- }
- i++;
- set >>= 1;
- }
- }
- return fdt;
- }
- struct files_struct *get_files_struct(struct task_struct *task)
- {
- struct files_struct *files;
- task_lock(task);
- files = task->files;
- if (files)
- atomic_inc(&files->count);
- task_unlock(task);
- return files;
- }
- void put_files_struct(struct files_struct *files)
- {
- if (atomic_dec_and_test(&files->count)) {
- struct fdtable *fdt = close_files(files);
- /* free the arrays if they are not embedded */
- if (fdt != &files->fdtab)
- __free_fdtable(fdt);
- kmem_cache_free(files_cachep, files);
- }
- }
- void reset_files_struct(struct files_struct *files)
- {
- struct task_struct *tsk = current;
- struct files_struct *old;
- old = tsk->files;
- task_lock(tsk);
- tsk->files = files;
- task_unlock(tsk);
- put_files_struct(old);
- }
- void exit_files(struct task_struct *tsk)
- {
- struct files_struct * files = tsk->files;
- if (files) {
- task_lock(tsk);
- tsk->files = NULL;
- task_unlock(tsk);
- put_files_struct(files);
- }
- }
- struct files_struct init_files = {
- .count = ATOMIC_INIT(1),
- .fdt = &init_files.fdtab,
- .fdtab = {
- .max_fds = NR_OPEN_DEFAULT,
- .fd = &init_files.fd_array[0],
- .close_on_exec = init_files.close_on_exec_init,
- .open_fds = init_files.open_fds_init,
- .full_fds_bits = init_files.full_fds_bits_init,
- },
- .file_lock = __SPIN_LOCK_UNLOCKED(init_files.file_lock),
- .resize_wait = __WAIT_QUEUE_HEAD_INITIALIZER(init_files.resize_wait),
- };
- static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start)
- {
- unsigned int maxfd = fdt->max_fds;
- unsigned int maxbit = maxfd / BITS_PER_LONG;
- unsigned int bitbit = start / BITS_PER_LONG;
- bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG;
- if (bitbit > maxfd)
- return maxfd;
- if (bitbit > start)
- start = bitbit;
- return find_next_zero_bit(fdt->open_fds, maxfd, start);
- }
- /*
- * allocate a file descriptor, mark it busy.
- */
- int __alloc_fd(struct files_struct *files,
- unsigned start, unsigned end, unsigned flags)
- {
- unsigned int fd;
- int error;
- struct fdtable *fdt;
- spin_lock(&files->file_lock);
- repeat:
- fdt = files_fdtable(files);
- fd = start;
- if (fd < files->next_fd)
- fd = files->next_fd;
- if (fd < fdt->max_fds)
- fd = find_next_fd(fdt, fd);
- /*
- * N.B. For clone tasks sharing a files structure, this test
- * will limit the total number of files that can be opened.
- */
- error = -EMFILE;
- if (fd >= end)
- goto out;
- error = expand_files(files, fd);
- if (error < 0)
- goto out;
- /*
- * If we needed to expand the fs array we
- * might have blocked - try again.
- */
- if (error)
- goto repeat;
- if (start <= files->next_fd)
- files->next_fd = fd + 1;
- __set_open_fd(fd, fdt);
- if (flags & O_CLOEXEC)
- __set_close_on_exec(fd, fdt);
- else
- __clear_close_on_exec(fd, fdt);
- error = fd;
- #if 1
- /* Sanity check */
- if (rcu_access_pointer(fdt->fd[fd]) != NULL) {
- printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
- rcu_assign_pointer(fdt->fd[fd], NULL);
- }
- #endif
- out:
- spin_unlock(&files->file_lock);
- return error;
- }
- static int alloc_fd(unsigned start, unsigned flags)
- {
- return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags);
- }
- int __get_unused_fd_flags(unsigned flags, unsigned long nofile)
- {
- return __alloc_fd(current->files, 0, nofile, flags);
- }
- int get_unused_fd_flags(unsigned flags)
- {
- return __get_unused_fd_flags(flags, rlimit(RLIMIT_NOFILE));
- }
- EXPORT_SYMBOL(get_unused_fd_flags);
- static void __put_unused_fd(struct files_struct *files, unsigned int fd)
- {
- struct fdtable *fdt = files_fdtable(files);
- __clear_open_fd(fd, fdt);
- if (fd < files->next_fd)
- files->next_fd = fd;
- }
- void put_unused_fd(unsigned int fd)
- {
- struct files_struct *files = current->files;
- spin_lock(&files->file_lock);
- __put_unused_fd(files, fd);
- spin_unlock(&files->file_lock);
- }
- EXPORT_SYMBOL(put_unused_fd);
- /*
- * Install a file pointer in the fd array.
- *
- * The VFS is full of places where we drop the files lock between
- * setting the open_fds bitmap and installing the file in the file
- * array. At any such point, we are vulnerable to a dup2() race
- * installing a file in the array before us. We need to detect this and
- * fput() the struct file we are about to overwrite in this case.
- *
- * It should never happen - if we allow dup2() do it, _really_ bad things
- * will follow.
- *
- * NOTE: __fd_install() variant is really, really low-level; don't
- * use it unless you are forced to by truly lousy API shoved down
- * your throat. 'files' *MUST* be either current->files or obtained
- * by get_files_struct(current) done by whoever had given it to you,
- * or really bad things will happen. Normally you want to use
- * fd_install() instead.
- */
- void __fd_install(struct files_struct *files, unsigned int fd,
- struct file *file)
- {
- struct fdtable *fdt;
- rcu_read_lock_sched();
- if (unlikely(files->resize_in_progress)) {
- rcu_read_unlock_sched();
- spin_lock(&files->file_lock);
- fdt = files_fdtable(files);
- BUG_ON(fdt->fd[fd] != NULL);
- rcu_assign_pointer(fdt->fd[fd], file);
- spin_unlock(&files->file_lock);
- return;
- }
- /* coupled with smp_wmb() in expand_fdtable() */
- smp_rmb();
- fdt = rcu_dereference_sched(files->fdt);
- BUG_ON(fdt->fd[fd] != NULL);
- rcu_assign_pointer(fdt->fd[fd], file);
- rcu_read_unlock_sched();
- }
- /*
- * This consumes the "file" refcount, so callers should treat it
- * as if they had called fput(file).
- */
- void fd_install(unsigned int fd, struct file *file)
- {
- __fd_install(current->files, fd, file);
- }
- EXPORT_SYMBOL(fd_install);
- static struct file *pick_file(struct files_struct *files, unsigned fd)
- {
- struct file *file = NULL;
- struct fdtable *fdt;
- spin_lock(&files->file_lock);
- fdt = files_fdtable(files);
- if (fd >= fdt->max_fds)
- goto out_unlock;
- file = fdt->fd[fd];
- if (!file)
- goto out_unlock;
- rcu_assign_pointer(fdt->fd[fd], NULL);
- __put_unused_fd(files, fd);
- out_unlock:
- spin_unlock(&files->file_lock);
- return file;
- }
- /*
- * The same warnings as for __alloc_fd()/__fd_install() apply here...
- */
- int __close_fd(struct files_struct *files, unsigned fd)
- {
- struct file *file;
- file = pick_file(files, fd);
- if (!file)
- return -EBADF;
- return filp_close(file, files);
- }
- EXPORT_SYMBOL(__close_fd); /* for ksys_close() */
- /**
- * __close_range() - Close all file descriptors in a given range.
- *
- * @fd: starting file descriptor to close
- * @max_fd: last file descriptor to close
- *
- * This closes a range of file descriptors. All file descriptors
- * from @fd up to and including @max_fd are closed.
- */
- int __close_range(unsigned fd, unsigned max_fd, unsigned int flags)
- {
- unsigned int cur_max;
- struct task_struct *me = current;
- struct files_struct *cur_fds = me->files, *fds = NULL;
- if (flags & ~CLOSE_RANGE_UNSHARE)
- return -EINVAL;
- if (fd > max_fd)
- return -EINVAL;
- rcu_read_lock();
- cur_max = files_fdtable(cur_fds)->max_fds;
- rcu_read_unlock();
- /* cap to last valid index into fdtable */
- cur_max--;
- if (flags & CLOSE_RANGE_UNSHARE) {
- int ret;
- unsigned int max_unshare_fds = NR_OPEN_MAX;
- /*
- * If the requested range is greater than the current maximum,
- * we're closing everything so only copy all file descriptors
- * beneath the lowest file descriptor.
- */
- if (max_fd >= cur_max)
- max_unshare_fds = fd;
- ret = unshare_fd(CLONE_FILES, max_unshare_fds, &fds);
- if (ret)
- return ret;
- /*
- * We used to share our file descriptor table, and have now
- * created a private one, make sure we're using it below.
- */
- if (fds)
- swap(cur_fds, fds);
- }
- max_fd = min(max_fd, cur_max);
- while (fd <= max_fd) {
- struct file *file;
- file = pick_file(cur_fds, fd++);
- if (!file)
- continue;
- filp_close(file, cur_fds);
- cond_resched();
- }
- if (fds) {
- /*
- * We're done closing the files we were supposed to. Time to install
- * the new file descriptor table and drop the old one.
- */
- task_lock(me);
- me->files = cur_fds;
- task_unlock(me);
- put_files_struct(fds);
- }
- return 0;
- }
- /*
- * variant of __close_fd that gets a ref on the file for later fput.
- * The caller must ensure that filp_close() called on the file, and then
- * an fput().
- */
- int __close_fd_get_file(unsigned int fd, struct file **res)
- {
- struct files_struct *files = current->files;
- struct file *file;
- struct fdtable *fdt;
- spin_lock(&files->file_lock);
- fdt = files_fdtable(files);
- if (fd >= fdt->max_fds)
- goto out_unlock;
- file = fdt->fd[fd];
- if (!file)
- goto out_unlock;
- rcu_assign_pointer(fdt->fd[fd], NULL);
- __put_unused_fd(files, fd);
- spin_unlock(&files->file_lock);
- get_file(file);
- *res = file;
- return 0;
- out_unlock:
- spin_unlock(&files->file_lock);
- *res = NULL;
- return -ENOENT;
- }
- void do_close_on_exec(struct files_struct *files)
- {
- unsigned i;
- struct fdtable *fdt;
- /* exec unshares first */
- spin_lock(&files->file_lock);
- for (i = 0; ; i++) {
- unsigned long set;
- unsigned fd = i * BITS_PER_LONG;
- fdt = files_fdtable(files);
- if (fd >= fdt->max_fds)
- break;
- set = fdt->close_on_exec[i];
- if (!set)
- continue;
- fdt->close_on_exec[i] = 0;
- for ( ; set ; fd++, set >>= 1) {
- struct file *file;
- if (!(set & 1))
- continue;
- file = fdt->fd[fd];
- if (!file)
- continue;
- rcu_assign_pointer(fdt->fd[fd], NULL);
- __put_unused_fd(files, fd);
- spin_unlock(&files->file_lock);
- filp_close(file, files);
- cond_resched();
- spin_lock(&files->file_lock);
- }
- }
- spin_unlock(&files->file_lock);
- }
- static inline struct file *__fget_files_rcu(struct files_struct *files,
- unsigned int fd, fmode_t mask, unsigned int refs)
- {
- for (;;) {
- struct file *file;
- struct fdtable *fdt = rcu_dereference_raw(files->fdt);
- struct file __rcu **fdentry;
- if (unlikely(fd >= fdt->max_fds))
- return NULL;
- fdentry = fdt->fd + array_index_nospec(fd, fdt->max_fds);
- file = rcu_dereference_raw(*fdentry);
- if (unlikely(!file))
- return NULL;
- if (unlikely(file->f_mode & mask))
- return NULL;
- /*
- * Ok, we have a file pointer. However, because we do
- * this all locklessly under RCU, we may be racing with
- * that file being closed.
- *
- * Such a race can take two forms:
- *
- * (a) the file ref already went down to zero,
- * and get_file_rcu_many() fails. Just try
- * again:
- */
- if (unlikely(!get_file_rcu_many(file, refs)))
- continue;
- /*
- * (b) the file table entry has changed under us.
- * Note that we don't need to re-check the 'fdt->fd'
- * pointer having changed, because it always goes
- * hand-in-hand with 'fdt'.
- *
- * If so, we need to put our refs and try again.
- */
- if (unlikely(rcu_dereference_raw(files->fdt) != fdt) ||
- unlikely(rcu_dereference_raw(*fdentry) != file)) {
- fput_many(file, refs);
- continue;
- }
- /*
- * Ok, we have a ref to the file, and checked that it
- * still exists.
- */
- return file;
- }
- }
- static struct file *__fget_files(struct files_struct *files, unsigned int fd,
- fmode_t mask, unsigned int refs)
- {
- struct file *file;
- rcu_read_lock();
- file = __fget_files_rcu(files, fd, mask, refs);
- rcu_read_unlock();
- return file;
- }
- static inline struct file *__fget(unsigned int fd, fmode_t mask,
- unsigned int refs)
- {
- return __fget_files(current->files, fd, mask, refs);
- }
- struct file *fget_many(unsigned int fd, unsigned int refs)
- {
- return __fget(fd, FMODE_PATH, refs);
- }
- struct file *fget(unsigned int fd)
- {
- return __fget(fd, FMODE_PATH, 1);
- }
- EXPORT_SYMBOL(fget);
- struct file *fget_raw(unsigned int fd)
- {
- return __fget(fd, 0, 1);
- }
- EXPORT_SYMBOL(fget_raw);
- struct file *fget_task(struct task_struct *task, unsigned int fd)
- {
- struct file *file = NULL;
- task_lock(task);
- if (task->files)
- file = __fget_files(task->files, fd, 0, 1);
- task_unlock(task);
- return file;
- }
- /*
- * Lightweight file lookup - no refcnt increment if fd table isn't shared.
- *
- * You can use this instead of fget if you satisfy all of the following
- * conditions:
- * 1) You must call fput_light before exiting the syscall and returning control
- * to userspace (i.e. you cannot remember the returned struct file * after
- * returning to userspace).
- * 2) You must not call filp_close on the returned struct file * in between
- * calls to fget_light and fput_light.
- * 3) You must not clone the current task in between the calls to fget_light
- * and fput_light.
- *
- * The fput_needed flag returned by fget_light should be passed to the
- * corresponding fput_light.
- */
- static unsigned long __fget_light(unsigned int fd, fmode_t mask)
- {
- struct files_struct *files = current->files;
- struct file *file;
- if (atomic_read(&files->count) == 1) {
- file = __fcheck_files(files, fd);
- if (!file || unlikely(file->f_mode & mask))
- return 0;
- return (unsigned long)file;
- } else {
- file = __fget(fd, mask, 1);
- if (!file)
- return 0;
- return FDPUT_FPUT | (unsigned long)file;
- }
- }
- unsigned long __fdget(unsigned int fd)
- {
- return __fget_light(fd, FMODE_PATH);
- }
- EXPORT_SYMBOL(__fdget);
- unsigned long __fdget_raw(unsigned int fd)
- {
- return __fget_light(fd, 0);
- }
- unsigned long __fdget_pos(unsigned int fd)
- {
- unsigned long v = __fdget(fd);
- struct file *file = (struct file *)(v & ~3);
- if (file && (file->f_mode & FMODE_ATOMIC_POS)) {
- if (file_count(file) > 1) {
- v |= FDPUT_POS_UNLOCK;
- mutex_lock(&file->f_pos_lock);
- }
- }
- return v;
- }
- void __f_unlock_pos(struct file *f)
- {
- mutex_unlock(&f->f_pos_lock);
- }
- /*
- * We only lock f_pos if we have threads or if the file might be
- * shared with another process. In both cases we'll have an elevated
- * file count (done either by fdget() or by fork()).
- */
- void set_close_on_exec(unsigned int fd, int flag)
- {
- struct files_struct *files = current->files;
- struct fdtable *fdt;
- spin_lock(&files->file_lock);
- fdt = files_fdtable(files);
- if (flag)
- __set_close_on_exec(fd, fdt);
- else
- __clear_close_on_exec(fd, fdt);
- spin_unlock(&files->file_lock);
- }
- bool get_close_on_exec(unsigned int fd)
- {
- struct files_struct *files = current->files;
- struct fdtable *fdt;
- bool res;
- rcu_read_lock();
- fdt = files_fdtable(files);
- res = close_on_exec(fd, fdt);
- rcu_read_unlock();
- return res;
- }
- static int do_dup2(struct files_struct *files,
- struct file *file, unsigned fd, unsigned flags)
- __releases(&files->file_lock)
- {
- struct file *tofree;
- struct fdtable *fdt;
- /*
- * We need to detect attempts to do dup2() over allocated but still
- * not finished descriptor. NB: OpenBSD avoids that at the price of
- * extra work in their equivalent of fget() - they insert struct
- * file immediately after grabbing descriptor, mark it larval if
- * more work (e.g. actual opening) is needed and make sure that
- * fget() treats larval files as absent. Potentially interesting,
- * but while extra work in fget() is trivial, locking implications
- * and amount of surgery on open()-related paths in VFS are not.
- * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
- * deadlocks in rather amusing ways, AFAICS. All of that is out of
- * scope of POSIX or SUS, since neither considers shared descriptor
- * tables and this condition does not arise without those.
- */
- fdt = files_fdtable(files);
- tofree = fdt->fd[fd];
- if (!tofree && fd_is_open(fd, fdt))
- goto Ebusy;
- get_file(file);
- rcu_assign_pointer(fdt->fd[fd], file);
- __set_open_fd(fd, fdt);
- if (flags & O_CLOEXEC)
- __set_close_on_exec(fd, fdt);
- else
- __clear_close_on_exec(fd, fdt);
- spin_unlock(&files->file_lock);
- if (tofree)
- filp_close(tofree, files);
- return fd;
- Ebusy:
- spin_unlock(&files->file_lock);
- return -EBUSY;
- }
- int replace_fd(unsigned fd, struct file *file, unsigned flags)
- {
- int err;
- struct files_struct *files = current->files;
- if (!file)
- return __close_fd(files, fd);
- if (fd >= rlimit(RLIMIT_NOFILE))
- return -EBADF;
- spin_lock(&files->file_lock);
- err = expand_files(files, fd);
- if (unlikely(err < 0))
- goto out_unlock;
- return do_dup2(files, file, fd, flags);
- out_unlock:
- spin_unlock(&files->file_lock);
- return err;
- }
- /**
- * __receive_fd() - Install received file into file descriptor table
- *
- * @fd: fd to install into (if negative, a new fd will be allocated)
- * @file: struct file that was received from another process
- * @ufd: __user pointer to write new fd number to
- * @o_flags: the O_* flags to apply to the new fd entry
- *
- * Installs a received file into the file descriptor table, with appropriate
- * checks and count updates. Optionally writes the fd number to userspace, if
- * @ufd is non-NULL.
- *
- * This helper handles its own reference counting of the incoming
- * struct file.
- *
- * Returns newly install fd or -ve on error.
- */
- int __receive_fd(int fd, struct file *file, int __user *ufd, unsigned int o_flags)
- {
- int new_fd;
- int error;
- error = security_file_receive(file);
- if (error)
- return error;
- if (fd < 0) {
- new_fd = get_unused_fd_flags(o_flags);
- if (new_fd < 0)
- return new_fd;
- } else {
- new_fd = fd;
- }
- if (ufd) {
- error = put_user(new_fd, ufd);
- if (error) {
- if (fd < 0)
- put_unused_fd(new_fd);
- return error;
- }
- }
- if (fd < 0) {
- fd_install(new_fd, get_file(file));
- } else {
- error = replace_fd(new_fd, file, o_flags);
- if (error)
- return error;
- }
- /* Bump the sock usage counts, if any. */
- __receive_sock(file);
- return new_fd;
- }
- static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
- {
- int err = -EBADF;
- struct file *file;
- struct files_struct *files = current->files;
- if ((flags & ~O_CLOEXEC) != 0)
- return -EINVAL;
- if (unlikely(oldfd == newfd))
- return -EINVAL;
- if (newfd >= rlimit(RLIMIT_NOFILE))
- return -EBADF;
- spin_lock(&files->file_lock);
- err = expand_files(files, newfd);
- file = fcheck(oldfd);
- if (unlikely(!file))
- goto Ebadf;
- if (unlikely(err < 0)) {
- if (err == -EMFILE)
- goto Ebadf;
- goto out_unlock;
- }
- return do_dup2(files, file, newfd, flags);
- Ebadf:
- err = -EBADF;
- out_unlock:
- spin_unlock(&files->file_lock);
- return err;
- }
- SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
- {
- return ksys_dup3(oldfd, newfd, flags);
- }
- SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
- {
- if (unlikely(newfd == oldfd)) { /* corner case */
- struct files_struct *files = current->files;
- int retval = oldfd;
- rcu_read_lock();
- if (!fcheck_files(files, oldfd))
- retval = -EBADF;
- rcu_read_unlock();
- return retval;
- }
- return ksys_dup3(oldfd, newfd, 0);
- }
- SYSCALL_DEFINE1(dup, unsigned int, fildes)
- {
- int ret = -EBADF;
- struct file *file = fget_raw(fildes);
- if (file) {
- ret = get_unused_fd_flags(0);
- if (ret >= 0)
- fd_install(ret, file);
- else
- fput(file);
- }
- return ret;
- }
- int f_dupfd(unsigned int from, struct file *file, unsigned flags)
- {
- int err;
- if (from >= rlimit(RLIMIT_NOFILE))
- return -EINVAL;
- err = alloc_fd(from, flags);
- if (err >= 0) {
- get_file(file);
- fd_install(err, file);
- }
- return err;
- }
- int iterate_fd(struct files_struct *files, unsigned n,
- int (*f)(const void *, struct file *, unsigned),
- const void *p)
- {
- struct fdtable *fdt;
- int res = 0;
- if (!files)
- return 0;
- spin_lock(&files->file_lock);
- for (fdt = files_fdtable(files); n < fdt->max_fds; n++) {
- struct file *file;
- file = rcu_dereference_check_fdtable(files, fdt->fd[n]);
- if (!file)
- continue;
- res = f(p, file, n);
- if (res)
- break;
- }
- spin_unlock(&files->file_lock);
- return res;
- }
- EXPORT_SYMBOL(iterate_fd);
|