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authorTodd Kjos <tkjos@android.com>2017-11-27 09:32:33 -0800
committerMartijn Coenen <maco@android.com>2018-07-17 11:14:22 +0200
commitfbb4339c024d65c9eadbfc664d82bf8c5307ac18 (patch)
tree72a46d20a9d10c1f9660f8f63c4fba657c19265d
parent6f7e5f90350e92f056bb092c067c83b18a81136e (diff)
downloadlinux-linaro-stable-fbb4339c024d65c9eadbfc664d82bf8c5307ac18.tar.gz
UPSTREAM: binder: fix proc->files use-after-free
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.c44
1 files changed, 31 insertions, 13 deletions
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index dc7a4f5171c8..3d49fd1e391c 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -501,7 +501,8 @@ 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
@@ -547,6 +548,7 @@ 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;
@@ -943,20 +945,26 @@ 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;
}
/*
@@ -965,8 +973,10 @@ 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);
}
/*
@@ -976,9 +986,11 @@ 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 ||
@@ -986,7 +998,8 @@ 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;
}
@@ -4894,7 +4907,9 @@ 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:
@@ -4918,6 +4933,7 @@ 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;
@@ -5177,9 +5193,11 @@ 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)