diff options
author | Todd Kjos <tkjos@android.com> | 2017-11-27 09:32:33 -0800 |
---|---|---|
committer | Todd Kjos <tkjos@google.com> | 2019-02-01 11:47:51 -0800 |
commit | 08294da7686c64b33c313ec474933a3a9562f37f (patch) | |
tree | 3aea496b846b072447e6f4eff2b5832d15139d8b | |
parent | 832d4c8785ba8f7f01119ab4d345cdb565d6c739 (diff) |
UPSTREAM: binder: fix proc->files use-after-freeASB-2019-02-05_4.4-o
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>
Cc: stable <stable@vger.kernel.org> # 4.14
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 7f3dc0088b98533f17128058fac73cd8b2752ef1)
Change-Id: I40982bb0b4615bda5459538c20eb2a913964042c
-rw-r--r-- | drivers/android/binder.c | 44 |
1 files changed, 31 insertions, 13 deletions
diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 6f0349b3ac0a..46de2d47d49d 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -506,7 +506,8 @@ struct binder_priority { * @tsk task_struct for group_leader of process * (invariant after initialized) * @files files_struct for process - * (invariant after initialized) + * (protected by @files_lock) + * @files_lock mutex to protect @files * @deferred_work_node: element for binder_deferred_list * (protected by binder_deferred_lock) * @deferred_work: bitmap of deferred work to perform @@ -554,6 +555,7 @@ struct binder_proc { int pid; struct task_struct *tsk; struct files_struct *files; + struct mutex files_lock; struct hlist_node deferred_work_node; int deferred_work; bool is_dead; @@ -904,20 +906,26 @@ static void binder_inc_node_tmpref_ilocked(struct binder_node *node); static int task_get_unused_fd_flags(struct binder_proc *proc, int flags) { - struct files_struct *files = proc->files; unsigned long rlim_cur; unsigned long irqs; + int ret; - if (files == NULL) - return -ESRCH; - - if (!lock_task_sighand(proc->tsk, &irqs)) - return -EMFILE; - + mutex_lock(&proc->files_lock); + if (proc->files == NULL) { + ret = -ESRCH; + goto err; + } + if (!lock_task_sighand(proc->tsk, &irqs)) { + ret = -EMFILE; + goto err; + } rlim_cur = task_rlimit(proc->tsk, RLIMIT_NOFILE); unlock_task_sighand(proc->tsk, &irqs); - return __alloc_fd(files, 0, rlim_cur, flags); + ret = __alloc_fd(proc->files, 0, rlim_cur, flags); +err: + mutex_unlock(&proc->files_lock); + return ret; } /* @@ -926,8 +934,10 @@ static int task_get_unused_fd_flags(struct binder_proc *proc, int flags) static void task_fd_install( struct binder_proc *proc, unsigned int fd, struct file *file) { + mutex_lock(&proc->files_lock); if (proc->files) __fd_install(proc->files, fd, file); + mutex_unlock(&proc->files_lock); } /* @@ -937,9 +947,11 @@ static long task_close_fd(struct binder_proc *proc, unsigned int fd) { int retval; - if (proc->files == NULL) - return -ESRCH; - + mutex_lock(&proc->files_lock); + if (proc->files == NULL) { + retval = -ESRCH; + goto err; + } retval = __close_fd(proc->files, fd); /* can't restart close syscall because file table entry was cleared */ if (unlikely(retval == -ERESTARTSYS || @@ -947,7 +959,8 @@ static long task_close_fd(struct binder_proc *proc, unsigned int fd) retval == -ERESTARTNOHAND || retval == -ERESTART_RESTARTBLOCK)) retval = -EINTR; - +err: + mutex_unlock(&proc->files_lock); return retval; } @@ -4781,7 +4794,9 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma) ret = binder_alloc_mmap_handler(&proc->alloc, vma); if (ret) return ret; + mutex_lock(&proc->files_lock); proc->files = get_files_struct(current); + mutex_unlock(&proc->files_lock); return 0; err_bad_arg: @@ -4805,6 +4820,7 @@ static int binder_open(struct inode *nodp, struct file *filp) spin_lock_init(&proc->outer_lock); get_task_struct(current->group_leader); proc->tsk = current->group_leader; + mutex_init(&proc->files_lock); INIT_LIST_HEAD(&proc->todo); if (binder_supported_policy(current->policy)) { proc->default_priority.sched_policy = current->policy; @@ -5064,9 +5080,11 @@ static void binder_deferred_func(struct work_struct *work) files = NULL; if (defer & BINDER_DEFERRED_PUT_FILES) { + mutex_lock(&proc->files_lock); files = proc->files; if (files) proc->files = NULL; + mutex_unlock(&proc->files_lock); } if (defer & BINDER_DEFERRED_FLUSH) |