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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
commitace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch)
treeb2d64bc10158fdd5497876388cd68142ca374ed3 /fs/file.c
parentInitial commit. (diff)
downloadlinux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz
linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'fs/file.c')
-rw-r--r--fs/file.c1336
1 files changed, 1336 insertions, 0 deletions
diff --git a/fs/file.c b/fs/file.c
new file mode 100644
index 0000000000..3e4a4dfa38
--- /dev/null
+++ b/fs/file.c
@@ -0,0 +1,1336 @@
+// 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>
+
+#include "internal.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;
+}
+
+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 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.
+ */
+static int alloc_fd(unsigned start, unsigned end, unsigned flags)
+{
+ struct files_struct *files = current->files;
+ 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;
+}
+
+int __get_unused_fd_flags(unsigned flags, unsigned long nofile)
+{
+ return alloc_fd(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.
+ *
+ * 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)
+{
+ struct files_struct *files = current->files;
+ 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();
+}
+
+EXPORT_SYMBOL(fd_install);
+
+/**
+ * pick_file - return file associatd with fd
+ * @files: file struct to retrieve file from
+ * @fd: file descriptor to retrieve file for
+ *
+ * Context: files_lock must be held.
+ *
+ * Returns: The file associated with @fd (NULL if @fd is not open)
+ */
+static struct file *pick_file(struct files_struct *files, unsigned fd)
+{
+ struct fdtable *fdt = files_fdtable(files);
+ struct file *file;
+
+ if (fd >= fdt->max_fds)
+ return NULL;
+
+ fd = array_index_nospec(fd, fdt->max_fds);
+ file = fdt->fd[fd];
+ if (file) {
+ rcu_assign_pointer(fdt->fd[fd], NULL);
+ __put_unused_fd(files, fd);
+ }
+ return file;
+}
+
+int close_fd(unsigned fd)
+{
+ struct files_struct *files = current->files;
+ struct file *file;
+
+ spin_lock(&files->file_lock);
+ file = pick_file(files, fd);
+ spin_unlock(&files->file_lock);
+ if (!file)
+ return -EBADF;
+
+ return filp_close(file, files);
+}
+EXPORT_SYMBOL(close_fd); /* for ksys_close() */
+
+/**
+ * last_fd - return last valid index into fd table
+ * @fdt: File descriptor table.
+ *
+ * Context: Either rcu read lock or files_lock must be held.
+ *
+ * Returns: Last valid index into fdtable.
+ */
+static inline unsigned last_fd(struct fdtable *fdt)
+{
+ return fdt->max_fds - 1;
+}
+
+static inline void __range_cloexec(struct files_struct *cur_fds,
+ unsigned int fd, unsigned int max_fd)
+{
+ struct fdtable *fdt;
+
+ /* make sure we're using the correct maximum value */
+ spin_lock(&cur_fds->file_lock);
+ fdt = files_fdtable(cur_fds);
+ max_fd = min(last_fd(fdt), max_fd);
+ if (fd <= max_fd)
+ bitmap_set(fdt->close_on_exec, fd, max_fd - fd + 1);
+ spin_unlock(&cur_fds->file_lock);
+}
+
+static inline void __range_close(struct files_struct *files, unsigned int fd,
+ unsigned int max_fd)
+{
+ struct file *file;
+ unsigned n;
+
+ spin_lock(&files->file_lock);
+ n = last_fd(files_fdtable(files));
+ max_fd = min(max_fd, n);
+
+ for (; fd <= max_fd; fd++) {
+ file = pick_file(files, fd);
+ if (file) {
+ spin_unlock(&files->file_lock);
+ filp_close(file, files);
+ cond_resched();
+ spin_lock(&files->file_lock);
+ } else if (need_resched()) {
+ spin_unlock(&files->file_lock);
+ cond_resched();
+ spin_lock(&files->file_lock);
+ }
+ }
+ spin_unlock(&files->file_lock);
+}
+
+/**
+ * __close_range() - Close all file descriptors in a given range.
+ *
+ * @fd: starting file descriptor to close
+ * @max_fd: last file descriptor to close
+ * @flags: CLOSE_RANGE flags.
+ *
+ * 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)
+{
+ struct task_struct *me = current;
+ struct files_struct *cur_fds = me->files, *fds = NULL;
+
+ if (flags & ~(CLOSE_RANGE_UNSHARE | CLOSE_RANGE_CLOEXEC))
+ return -EINVAL;
+
+ if (fd > max_fd)
+ return -EINVAL;
+
+ if (flags & CLOSE_RANGE_UNSHARE) {
+ int ret;
+ unsigned int max_unshare_fds = NR_OPEN_MAX;
+
+ /*
+ * If the caller requested all fds to be made cloexec we always
+ * copy all of the file descriptors since they still want to
+ * use them.
+ */
+ if (!(flags & CLOSE_RANGE_CLOEXEC)) {
+ /*
+ * 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.
+ */
+ rcu_read_lock();
+ if (max_fd >= last_fd(files_fdtable(cur_fds)))
+ max_unshare_fds = fd;
+ rcu_read_unlock();
+ }
+
+ 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);
+ }
+
+ if (flags & CLOSE_RANGE_CLOEXEC)
+ __range_cloexec(cur_fds, fd, max_fd);
+ else
+ __range_close(cur_fds, fd, max_fd);
+
+ 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;
+}
+
+/*
+ * See close_fd_get_file() below, this variant assumes current->files->file_lock
+ * is held.
+ */
+struct file *__close_fd_get_file(unsigned int fd)
+{
+ return pick_file(current->files, fd);
+}
+
+/*
+ * 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.
+ */
+struct file *close_fd_get_file(unsigned int fd)
+{
+ struct files_struct *files = current->files;
+ struct file *file;
+
+ spin_lock(&files->file_lock);
+ file = pick_file(files, fd);
+ spin_unlock(&files->file_lock);
+
+ return file;
+}
+
+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)
+{
+ 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() fails. Just try again:
+ */
+ if (unlikely(!get_file_rcu(file)))
+ 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 ref and try again.
+ */
+ if (unlikely(rcu_dereference_raw(files->fdt) != fdt) ||
+ unlikely(rcu_dereference_raw(*fdentry) != file)) {
+ fput(file);
+ 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)
+{
+ struct file *file;
+
+ rcu_read_lock();
+ file = __fget_files_rcu(files, fd, mask);
+ rcu_read_unlock();
+
+ return file;
+}
+
+static inline struct file *__fget(unsigned int fd, fmode_t mask)
+{
+ return __fget_files(current->files, fd, mask);
+}
+
+struct file *fget(unsigned int fd)
+{
+ return __fget(fd, FMODE_PATH);
+}
+EXPORT_SYMBOL(fget);
+
+struct file *fget_raw(unsigned int fd)
+{
+ return __fget(fd, 0);
+}
+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);
+ task_unlock(task);
+
+ return file;
+}
+
+struct file *task_lookup_fd_rcu(struct task_struct *task, unsigned int fd)
+{
+ /* Must be called with rcu_read_lock held */
+ struct files_struct *files;
+ struct file *file = NULL;
+
+ task_lock(task);
+ files = task->files;
+ if (files)
+ file = files_lookup_fd_rcu(files, fd);
+ task_unlock(task);
+
+ return file;
+}
+
+struct file *task_lookup_next_fd_rcu(struct task_struct *task, unsigned int *ret_fd)
+{
+ /* Must be called with rcu_read_lock held */
+ struct files_struct *files;
+ unsigned int fd = *ret_fd;
+ struct file *file = NULL;
+
+ task_lock(task);
+ files = task->files;
+ if (files) {
+ for (; fd < files_fdtable(files)->max_fds; fd++) {
+ file = files_lookup_fd_rcu(files, fd);
+ if (file)
+ break;
+ }
+ }
+ task_unlock(task);
+ *ret_fd = fd;
+ return file;
+}
+EXPORT_SYMBOL(task_lookup_next_fd_rcu);
+
+/*
+ * 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 another thread is concurrently calling close_fd() followed
+ * by put_files_struct(), we must not observe the old table
+ * entry combined with the new refcount - otherwise we could
+ * return a file that is concurrently being freed.
+ *
+ * atomic_read_acquire() pairs with atomic_dec_and_test() in
+ * put_files_struct().
+ */
+ if (atomic_read_acquire(&files->count) == 1) {
+ file = files_lookup_fd_raw(files, fd);
+ if (!file || unlikely(file->f_mode & mask))
+ return 0;
+ return (unsigned long)file;
+ } else {
+ file = __fget(fd, mask);
+ 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);
+}
+
+/*
+ * Try to avoid f_pos locking. We only need it if the
+ * file is marked for FMODE_ATOMIC_POS, and it can be
+ * accessed multiple ways.
+ *
+ * Always do it for directories, because pidfd_getfd()
+ * can make a file accessible even if it otherwise would
+ * not be, and for directories this is a correctness
+ * issue, not a "POSIX requirement".
+ */
+static inline bool file_needs_f_pos_lock(struct file *file)
+{
+ return (file->f_mode & FMODE_ATOMIC_POS) &&
+ (file_count(file) > 1 || file->f_op->iterate_shared);
+}
+
+unsigned long __fdget_pos(unsigned int fd)
+{
+ unsigned long v = __fdget(fd);
+ struct file *file = (struct file *)(v & ~3);
+
+ if (file && file_needs_f_pos_lock(file)) {
+ 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(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
+ * @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(struct file *file, int __user *ufd, unsigned int o_flags)
+{
+ int new_fd;
+ int error;
+
+ error = security_file_receive(file);
+ if (error)
+ return error;
+
+ new_fd = get_unused_fd_flags(o_flags);
+ if (new_fd < 0)
+ return new_fd;
+
+ if (ufd) {
+ error = put_user(new_fd, ufd);
+ if (error) {
+ put_unused_fd(new_fd);
+ return error;
+ }
+ }
+
+ fd_install(new_fd, get_file(file));
+ __receive_sock(file);
+ return new_fd;
+}
+
+int receive_fd_replace(int new_fd, struct file *file, unsigned int o_flags)
+{
+ int error;
+
+ error = security_file_receive(file);
+ if (error)
+ return error;
+ error = replace_fd(new_fd, file, o_flags);
+ if (error)
+ return error;
+ __receive_sock(file);
+ return new_fd;
+}
+
+int receive_fd(struct file *file, unsigned int o_flags)
+{
+ return __receive_fd(file, NULL, o_flags);
+}
+EXPORT_SYMBOL_GPL(receive_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 = files_lookup_fd_locked(files, 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 (!files_lookup_fd_rcu(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)
+{
+ unsigned long nofile = rlimit(RLIMIT_NOFILE);
+ int err;
+ if (from >= nofile)
+ return -EINVAL;
+ err = alloc_fd(from, nofile, 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);