cifs: fail i/o on soft mounts if sessionsetup errors out

[sagit-ice-cold/kernel_xiaomi_msm8998.git] / fs / aio.c

diff --git a/fs/aio.c b/fs/aio.c
index 155f842..7187d03 100644 (file)
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -40,6 +40,7 @@
 #include <linux/ramfs.h>
 #include <linux/percpu-refcount.h>
 #include <linux/mount.h>
+#include <linux/nospec.h>
 
 #include <asm/kmap_types.h>
 #include <asm/uaccess.h>
@@ -68,9 +69,9 @@ struct aio_ring {
 #define AIO_RING_PAGES 8
 
 struct kioctx_table {
-       struct rcu_head rcu;
-       unsigned        nr;
-       struct kioctx   *table[];
+       struct rcu_head         rcu;
+       unsigned                nr;
+       struct kioctx __rcu     *table[];
 };
 
 struct kioctx_cpu {
@@ -115,7 +116,8 @@ struct kioctx {
        struct page             **ring_pages;
        long                    nr_pages;
 
-       struct work_struct      free_work;
+       struct rcu_head         free_rcu;
+       struct work_struct      free_work;      /* see free_ioctx() */
 
        /*
         * signals when all in-flight requests are done
@@ -239,7 +241,12 @@ static struct dentry *aio_mount(struct file_system_type *fs_type,
        static const struct dentry_operations ops = {
                .d_dname        = simple_dname,
        };
-       return mount_pseudo(fs_type, "aio:", NULL, &ops, AIO_RING_MAGIC);
+       struct dentry *root = mount_pseudo(fs_type, "aio:", NULL, &ops,
+                                          AIO_RING_MAGIC);
+
+       if (!IS_ERR(root))
+               root->d_sb->s_iflags |= SB_I_NOEXEC;
+       return root;
 }
 
 /* aio_setup
@@ -321,7 +328,7 @@ static int aio_ring_mremap(struct vm_area_struct *vma)
        for (i = 0; i < table->nr; i++) {
                struct kioctx *ctx;
 
-               ctx = table->table[i];
+               ctx = rcu_dereference(table->table[i]);
                if (ctx && ctx->aio_ring_file == file) {
                        if (!atomic_read(&ctx->dead)) {
                                ctx->user_id = ctx->mmap_base = vma->vm_start;
@@ -568,6 +575,12 @@ static int kiocb_cancel(struct aio_kiocb *kiocb)
        return cancel(&kiocb->common);
 }
 
+/*
+ * free_ioctx() should be RCU delayed to synchronize against the RCU
+ * protected lookup_ioctx() and also needs process context to call
+ * aio_free_ring(), so the double bouncing through kioctx->free_rcu and
+ * ->free_work.
+ */
 static void free_ioctx(struct work_struct *work)
 {
        struct kioctx *ctx = container_of(work, struct kioctx, free_work);
@@ -581,6 +594,14 @@ static void free_ioctx(struct work_struct *work)
        kmem_cache_free(kioctx_cachep, ctx);
 }
 
+static void free_ioctx_rcufn(struct rcu_head *head)
+{
+       struct kioctx *ctx = container_of(head, struct kioctx, free_rcu);
+
+       INIT_WORK(&ctx->free_work, free_ioctx);
+       schedule_work(&ctx->free_work);
+}
+
 static void free_ioctx_reqs(struct percpu_ref *ref)
 {
        struct kioctx *ctx = container_of(ref, struct kioctx, reqs);
@@ -589,8 +610,8 @@ static void free_ioctx_reqs(struct percpu_ref *ref)
        if (ctx->rq_wait && atomic_dec_and_test(&ctx->rq_wait->count))
                complete(&ctx->rq_wait->comp);
 
-       INIT_WORK(&ctx->free_work, free_ioctx);
-       schedule_work(&ctx->free_work);
+       /* Synchronize against RCU protected table->table[] dereferences */
+       call_rcu(&ctx->free_rcu, free_ioctx_rcufn);
 }
 
 /*
@@ -608,9 +629,8 @@ static void free_ioctx_users(struct percpu_ref *ref)
        while (!list_empty(&ctx->active_reqs)) {
                req = list_first_entry(&ctx->active_reqs,
                                       struct aio_kiocb, ki_list);
-
-               list_del_init(&req->ki_list);
                kiocb_cancel(req);
+               list_del_init(&req->ki_list);
        }
 
        spin_unlock_irq(&ctx->ctx_lock);
@@ -631,9 +651,9 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
        while (1) {
                if (table)
                        for (i = 0; i < table->nr; i++)
-                               if (!table->table[i]) {
+                               if (!rcu_access_pointer(table->table[i])) {
                                        ctx->id = i;
-                                       table->table[i] = ctx;
+                                       rcu_assign_pointer(table->table[i], ctx);
                                        spin_unlock(&mm->ioctx_lock);
 
                                        /* While kioctx setup is in progress,
@@ -808,11 +828,11 @@ static int kill_ioctx(struct mm_struct *mm, struct kioctx *ctx,
        }
 
        table = rcu_dereference_raw(mm->ioctx_table);
-       WARN_ON(ctx != table->table[ctx->id]);
-       table->table[ctx->id] = NULL;
+       WARN_ON(ctx != rcu_access_pointer(table->table[ctx->id]));
+       RCU_INIT_POINTER(table->table[ctx->id], NULL);
        spin_unlock(&mm->ioctx_lock);
 
-       /* percpu_ref_kill() will do the necessary call_rcu() */
+       /* free_ioctx_reqs() will do the necessary RCU synchronization */
        wake_up_all(&ctx->wait);
 
        /*
@@ -854,7 +874,8 @@ void exit_aio(struct mm_struct *mm)
 
        skipped = 0;
        for (i = 0; i < table->nr; ++i) {
-               struct kioctx *ctx = table->table[i];
+               struct kioctx *ctx =
+                       rcu_dereference_protected(table->table[i], true);
 
                if (!ctx) {
                        skipped++;
@@ -1043,10 +1064,11 @@ static struct kioctx *lookup_ioctx(unsigned long ctx_id)
        if (!table || id >= table->nr)
                goto out;
 
-       ctx = table->table[id];
+       id = array_index_nospec(id, table->nr);
+       ctx = rcu_dereference(table->table[id]);
        if (ctx && ctx->user_id == ctx_id) {
-               percpu_ref_get(&ctx->users);
-               ret = ctx;
+               if (percpu_ref_tryget_live(&ctx->users))
+                       ret = ctx;
        }
 out:
        rcu_read_unlock();