Staging: binder: Keep a reference to the files_struct while the driver is mmapped
This prevents breaking fget_light if a single threaded application
allows incoming file descriptors (in replies or on nodes).
Should also prevent inserting a file in the wrong files_struct if the
receving process execs in the middle of a transaction (between
task_get_unused_fd_flags and task_fd_install).
Signed-off-by: Arve Hjønnevåg <arve@android.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/staging/android/binder.c b/drivers/staging/android/binder.c
index 64f95ee..09962e8 100644
--- a/drivers/staging/android/binder.c
+++ b/drivers/staging/android/binder.c
@@ -41,6 +41,8 @@
static struct proc_dir_entry *binder_proc_dir_entry_root;
static struct proc_dir_entry *binder_proc_dir_entry_proc;
static struct hlist_head binder_dead_nodes;
+static HLIST_HEAD(binder_release_files_list);
+static DEFINE_MUTEX(binder_release_files_lock);
static int binder_read_proc_proc(
char *page, char **start, off_t off, int count, int *eof, void *data);
@@ -241,6 +243,8 @@
int pid;
struct vm_area_struct *vma;
struct task_struct *tsk;
+ struct files_struct *files;
+ struct hlist_node release_files_node;
void *buffer;
size_t user_buffer_offset;
@@ -309,9 +313,9 @@
/*
* copied from get_unused_fd_flags
*/
-int task_get_unused_fd_flags(struct task_struct *tsk, int flags)
+int task_get_unused_fd_flags(struct binder_proc *proc, int flags)
{
- struct files_struct *files = get_files_struct(tsk);
+ struct files_struct *files = proc->files;
int fd, error;
struct fdtable *fdt;
unsigned long rlim_cur;
@@ -333,9 +337,9 @@
* will limit the total number of files that can be opened.
*/
rlim_cur = 0;
- if (lock_task_sighand(tsk, &irqs)) {
- rlim_cur = tsk->signal->rlim[RLIMIT_NOFILE].rlim_cur;
- unlock_task_sighand(tsk, &irqs);
+ if (lock_task_sighand(proc->tsk, &irqs)) {
+ rlim_cur = proc->tsk->signal->rlim[RLIMIT_NOFILE].rlim_cur;
+ unlock_task_sighand(proc->tsk, &irqs);
}
if (fd >= rlim_cur)
goto out;
@@ -371,7 +375,6 @@
out:
spin_unlock(&files->file_lock);
- put_files_struct(files);
return error;
}
@@ -379,9 +382,9 @@
* copied from fd_install
*/
static void task_fd_install(
- struct task_struct *tsk, unsigned int fd, struct file *file)
+ struct binder_proc *proc, unsigned int fd, struct file *file)
{
- struct files_struct *files = get_files_struct(tsk);
+ struct files_struct *files = proc->files;
struct fdtable *fdt;
if (files == NULL)
@@ -392,7 +395,6 @@
BUG_ON(fdt->fd[fd] != NULL);
rcu_assign_pointer(fdt->fd[fd], file);
spin_unlock(&files->file_lock);
- put_files_struct(files);
}
/*
@@ -409,10 +411,10 @@
/*
* copied from sys_close
*/
-static long task_close_fd(struct task_struct *tsk, unsigned int fd)
+static long task_close_fd(struct binder_proc *proc, unsigned int fd)
{
struct file *filp;
- struct files_struct *files = get_files_struct(tsk);
+ struct files_struct *files = proc->files;
struct fdtable *fdt;
int retval;
@@ -439,12 +441,10 @@
retval == -ERESTART_RESTARTBLOCK))
retval = -EINTR;
- put_files_struct(files);
return retval;
out_unlock:
spin_unlock(&files->file_lock);
- put_files_struct(files);
return -EBADF;
}
@@ -1549,13 +1549,13 @@
return_error = BR_FAILED_REPLY;
goto err_fget_failed;
}
- target_fd = task_get_unused_fd_flags(target_proc->tsk, O_CLOEXEC);
+ target_fd = task_get_unused_fd_flags(target_proc, O_CLOEXEC);
if (target_fd < 0) {
fput(file);
return_error = BR_FAILED_REPLY;
goto err_get_unused_fd_failed;
}
- task_fd_install(target_proc->tsk, target_fd, file);
+ task_fd_install(target_proc, target_fd, file);
if (binder_debug_mask & BINDER_DEBUG_TRANSACTION)
printk(KERN_INFO " fd %ld -> %d\n", fp->handle, target_fd);
/* TODO: fput? */
@@ -1698,7 +1698,7 @@
if (binder_debug_mask & BINDER_DEBUG_TRANSACTION)
printk(KERN_INFO " fd %ld\n", fp->handle);
if (failed_at)
- task_close_fd(proc->tsk, fp->handle);
+ task_close_fd(proc, fp->handle);
break;
default:
@@ -2663,6 +2663,34 @@
(unsigned long)pgprot_val(vma->vm_page_prot));
dump_stack();
}
+
+static void binder_release_files(struct work_struct *work)
+{
+ struct binder_proc *proc;
+ struct files_struct *files;
+ do {
+ mutex_lock(&binder_lock);
+ mutex_lock(&binder_release_files_lock);
+ if (!hlist_empty(&binder_release_files_list)) {
+ proc = hlist_entry(binder_release_files_list.first,
+ struct binder_proc, release_files_node);
+ hlist_del_init(&proc->release_files_node);
+ files = proc->files;
+ if (files)
+ proc->files = NULL;
+ } else {
+ proc = NULL;
+ files = NULL;
+ }
+ mutex_unlock(&binder_release_files_lock);
+ mutex_unlock(&binder_lock);
+ if (files)
+ put_files_struct(files);
+ } while (proc);
+}
+
+static DECLARE_WORK(binder_release_files_work, binder_release_files);
+
static void binder_vma_close(struct vm_area_struct *vma)
{
struct binder_proc *proc = vma->vm_private_data;
@@ -2673,6 +2701,13 @@
(vma->vm_end - vma->vm_start) / SZ_1K, vma->vm_flags,
(unsigned long)pgprot_val(vma->vm_page_prot));
proc->vma = NULL;
+ mutex_lock(&binder_release_files_lock);
+ if (proc->files) {
+ hlist_add_head(&proc->release_files_node,
+ &binder_release_files_list);
+ schedule_work(&binder_release_files_work);
+ }
+ mutex_unlock(&binder_release_files_lock);
}
static struct vm_operations_struct binder_vm_ops = {
@@ -2751,6 +2786,7 @@
binder_insert_free_buffer(proc, buffer);
proc->free_async_space = proc->buffer_size / 2;
barrier();
+ proc->files = get_files_struct(current);
proc->vma = vma;
/*printk(KERN_INFO "binder_mmap: %d %lx-%lx maps %p\n", proc->pid, vma->vm_start, vma->vm_end, proc->buffer);*/
@@ -2831,6 +2867,7 @@
struct hlist_node *pos;
struct binder_transaction *t;
struct rb_node *n;
+ struct files_struct *files;
struct binder_proc *proc = filp->private_data;
int threads, nodes, incoming_refs, outgoing_refs, buffers, active_transactions, page_count;
@@ -2840,6 +2877,14 @@
remove_proc_entry(strbuf, binder_proc_dir_entry_proc);
}
mutex_lock(&binder_lock);
+ mutex_lock(&binder_release_files_lock);
+ if (!hlist_unhashed(&proc->release_files_node))
+ hlist_del(&proc->release_files_node);
+ files = proc->files;
+ if (files)
+ proc->files = NULL;
+ mutex_unlock(&binder_release_files_lock);
+
hlist_del(&proc->proc_node);
if (binder_context_mgr_node && binder_context_mgr_node->proc == proc) {
if (binder_debug_mask & BINDER_DEBUG_DEAD_BINDER)
@@ -2937,6 +2982,8 @@
proc->pid, threads, nodes, incoming_refs, outgoing_refs, active_transactions, buffers, page_count);
kfree(proc);
+ if (files)
+ put_files_struct(files);
return 0;
}