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binder: fix proc->files use-after-free
commit 7f3dc0088b
upstream.
proc->files cleanup is initiated by binder_vma_close. Therefore
a reference on the binder_proc is not enough to prevent the
files_struct from being released while the binder_proc still has
a reference. This can lead to an attempt to dereference the
stale pointer obtained from proc->files prior to proc->files
cleanup. This has been seen once in task_get_unused_fd_flags()
when __alloc_fd() is called with a stale "files".
The fix is to protect proc->files with a mutex to prevent cleanup
while in use.
Signed-off-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
412091e27d
commit
c0d75dacff
1 changed files with 29 additions and 12 deletions
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@ -302,6 +302,7 @@ struct binder_proc {
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struct mm_struct *vma_vm_mm;
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struct mm_struct *vma_vm_mm;
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struct task_struct *tsk;
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struct task_struct *tsk;
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struct files_struct *files;
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struct files_struct *files;
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struct mutex files_lock;
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struct hlist_node deferred_work_node;
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struct hlist_node deferred_work_node;
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int deferred_work;
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int deferred_work;
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void *buffer;
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void *buffer;
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@ -375,20 +376,26 @@ binder_defer_work(struct binder_proc *proc, enum binder_deferred_state defer);
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static int task_get_unused_fd_flags(struct binder_proc *proc, int flags)
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static int task_get_unused_fd_flags(struct binder_proc *proc, int flags)
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{
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{
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struct files_struct *files = proc->files;
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unsigned long rlim_cur;
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unsigned long rlim_cur;
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unsigned long irqs;
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unsigned long irqs;
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int ret;
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if (files == NULL)
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mutex_lock(&proc->files_lock);
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return -ESRCH;
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if (proc->files == NULL) {
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ret = -ESRCH;
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if (!lock_task_sighand(proc->tsk, &irqs))
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goto err;
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return -EMFILE;
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}
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if (!lock_task_sighand(proc->tsk, &irqs)) {
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ret = -EMFILE;
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goto err;
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}
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rlim_cur = task_rlimit(proc->tsk, RLIMIT_NOFILE);
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rlim_cur = task_rlimit(proc->tsk, RLIMIT_NOFILE);
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unlock_task_sighand(proc->tsk, &irqs);
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unlock_task_sighand(proc->tsk, &irqs);
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return __alloc_fd(files, 0, rlim_cur, flags);
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ret = __alloc_fd(proc->files, 0, rlim_cur, flags);
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err:
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mutex_unlock(&proc->files_lock);
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return ret;
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}
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}
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/*
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/*
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@ -397,8 +404,10 @@ static int task_get_unused_fd_flags(struct binder_proc *proc, int flags)
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static void task_fd_install(
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static void task_fd_install(
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struct binder_proc *proc, unsigned int fd, struct file *file)
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struct binder_proc *proc, unsigned int fd, struct file *file)
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{
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{
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mutex_lock(&proc->files_lock);
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if (proc->files)
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if (proc->files)
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__fd_install(proc->files, fd, file);
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__fd_install(proc->files, fd, file);
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mutex_unlock(&proc->files_lock);
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}
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}
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/*
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/*
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@ -408,9 +417,11 @@ static long task_close_fd(struct binder_proc *proc, unsigned int fd)
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{
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{
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int retval;
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int retval;
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if (proc->files == NULL)
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mutex_lock(&proc->files_lock);
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return -ESRCH;
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if (proc->files == NULL) {
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retval = -ESRCH;
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goto err;
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}
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retval = __close_fd(proc->files, fd);
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retval = __close_fd(proc->files, fd);
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/* can't restart close syscall because file table entry was cleared */
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/* can't restart close syscall because file table entry was cleared */
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if (unlikely(retval == -ERESTARTSYS ||
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if (unlikely(retval == -ERESTARTSYS ||
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@ -418,7 +429,8 @@ static long task_close_fd(struct binder_proc *proc, unsigned int fd)
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retval == -ERESTARTNOHAND ||
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retval == -ERESTARTNOHAND ||
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retval == -ERESTART_RESTARTBLOCK))
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retval == -ERESTART_RESTARTBLOCK))
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retval = -EINTR;
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retval = -EINTR;
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err:
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mutex_unlock(&proc->files_lock);
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return retval;
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return retval;
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}
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}
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@ -2946,7 +2958,9 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma)
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binder_insert_free_buffer(proc, buffer);
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binder_insert_free_buffer(proc, buffer);
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proc->free_async_space = proc->buffer_size / 2;
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proc->free_async_space = proc->buffer_size / 2;
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barrier();
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barrier();
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mutex_lock(&proc->files_lock);
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proc->files = get_files_struct(current);
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proc->files = get_files_struct(current);
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mutex_unlock(&proc->files_lock);
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proc->vma = vma;
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proc->vma = vma;
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proc->vma_vm_mm = vma->vm_mm;
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proc->vma_vm_mm = vma->vm_mm;
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@ -2982,6 +2996,7 @@ static int binder_open(struct inode *nodp, struct file *filp)
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return -ENOMEM;
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return -ENOMEM;
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get_task_struct(current->group_leader);
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get_task_struct(current->group_leader);
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proc->tsk = current->group_leader;
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proc->tsk = current->group_leader;
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mutex_init(&proc->files_lock);
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INIT_LIST_HEAD(&proc->todo);
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INIT_LIST_HEAD(&proc->todo);
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init_waitqueue_head(&proc->wait);
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init_waitqueue_head(&proc->wait);
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proc->default_priority = task_nice(current);
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proc->default_priority = task_nice(current);
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@ -3220,9 +3235,11 @@ static void binder_deferred_func(struct work_struct *work)
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files = NULL;
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files = NULL;
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if (defer & BINDER_DEFERRED_PUT_FILES) {
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if (defer & BINDER_DEFERRED_PUT_FILES) {
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mutex_lock(&proc->files_lock);
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files = proc->files;
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files = proc->files;
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if (files)
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if (files)
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proc->files = NULL;
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proc->files = NULL;
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mutex_unlock(&proc->files_lock);
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}
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}
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if (defer & BINDER_DEFERRED_FLUSH)
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if (defer & BINDER_DEFERRED_FLUSH)
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