lib: logic_pio: Fix RCU usage

BugLink: https://bugs.launchpad.net/bugs/1843338
commit 06709e81c668f5f56c65b806895b278517bd44e0 upstream.

The traversing of io_range_list with list_for_each_entry_rcu()
is not properly protected by rcu_read_lock() and rcu_read_unlock(),
so add them.

These functions mark the critical section scope where the list is
protected for the reader, it cannot be  "reclaimed". Any updater - in
this case, the logical PIO registration functions - cannot update the
list until the reader exits this critical section.

In addition, the list traversing used in logic_pio_register_range()
does not need to use the rcu variant.

This is because we are already using io_range_mutex to guarantee mutual
exclusion from mutating the list.

Cc: stable@vger.kernel.org
Fixes: 031e3601869c ("lib: Add generic PIO mapping method")
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Wei Xu <xuwei5@hisilicon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/lib/logic_pio.c b/lib/logic_pio.c
index feea48fd1a0dd6ae7913b6fad19cc52e20664785..761296376fbc708585735981b678c58133601090 100644 (file)
--- a/lib/logic_pio.c
+++ b/lib/logic_pio.c
@@ -46,7 +46,7 @@ int logic_pio_register_range(struct logic_pio_hwaddr *new_range)
        end = new_range->hw_start + new_range->size;
 
        mutex_lock(&io_range_mutex);
-       list_for_each_entry_rcu(range, &io_range_list, list) {
+       list_for_each_entry(range, &io_range_list, list) {
                if (range->fwnode == new_range->fwnode) {
                        /* range already there */
                        goto end_register;
@@ -108,26 +108,38 @@ end_register:
  */
 struct logic_pio_hwaddr *find_io_range_by_fwnode(struct fwnode_handle *fwnode)
 {
-       struct logic_pio_hwaddr *range;
+       struct logic_pio_hwaddr *range, *found_range = NULL;
 
+       rcu_read_lock();
        list_for_each_entry_rcu(range, &io_range_list, list) {
-               if (range->fwnode == fwnode)
-                       return range;
+               if (range->fwnode == fwnode) {
+                       found_range = range;
+                       break;
+               }
        }
-       return NULL;
+       rcu_read_unlock();
+
+       return found_range;
 }
 
 /* Return a registered range given an input PIO token */
 static struct logic_pio_hwaddr *find_io_range(unsigned long pio)
 {
-       struct logic_pio_hwaddr *range;
+       struct logic_pio_hwaddr *range, *found_range = NULL;
 
+       rcu_read_lock();
        list_for_each_entry_rcu(range, &io_range_list, list) {
-               if (in_range(pio, range->io_start, range->size))
-                       return range;
+               if (in_range(pio, range->io_start, range->size)) {
+                       found_range = range;
+                       break;
+               }
        }
-       pr_err("PIO entry token %lx invalid\n", pio);
-       return NULL;
+       rcu_read_unlock();
+
+       if (!found_range)
+               pr_err("PIO entry token 0x%lx invalid\n", pio);
+
+       return found_range;
 }
 
 /**
@@ -180,14 +192,23 @@ unsigned long logic_pio_trans_cpuaddr(resource_size_t addr)
 {
        struct logic_pio_hwaddr *range;
 
+       rcu_read_lock();
        list_for_each_entry_rcu(range, &io_range_list, list) {
                if (range->flags != LOGIC_PIO_CPU_MMIO)
                        continue;
-               if (in_range(addr, range->hw_start, range->size))
-                       return addr - range->hw_start + range->io_start;
+               if (in_range(addr, range->hw_start, range->size)) {
+                       unsigned long cpuaddr;
+
+                       cpuaddr = addr - range->hw_start + range->io_start;
+
+                       rcu_read_unlock();
+                       return cpuaddr;
+               }
        }
-       pr_err("addr %llx not registered in io_range_list\n",
-              (unsigned long long) addr);
+       rcu_read_unlock();
+
+       pr_err("addr %pa not registered in io_range_list\n", &addr);
+
        return ~0UL;
 }