Fix: handle writes of length 0

[lttng-modules.git] / lib / ringbuffer / ring_buffer_backend.c

diff --git a/lib/ringbuffer/ring_buffer_backend.c b/lib/ringbuffer/ring_buffer_backend.c
index e8ad4c521cfb66440e51eb4ae9ca0930ea6528d6..8c9d2b7c54e7b583e896fec159349b2336a0fb21 100644 (file)
--- a/lib/ringbuffer/ring_buffer_backend.c
+++ b/lib/ringbuffer/ring_buffer_backend.c
@@ -253,7 +253,7 @@ void channel_backend_reset(struct channel_backend *chanb)
  *     Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
  */
 static
-int __cpuinit lib_ring_buffer_cpu_hp_callback(struct notifier_block *nb,
+int lib_ring_buffer_cpu_hp_callback(struct notifier_block *nb,
                                              unsigned long action,
                                              void *hcpu)
 {
@@ -559,7 +559,7 @@ EXPORT_SYMBOL_GPL(_lib_ring_buffer_memset);
 
 
 /**
- * lib_ring_buffer_copy_from_user - write user data to a ring_buffer buffer.
+ * lib_ring_buffer_copy_from_user_inatomic - write user data to a ring_buffer buffer.
  * @bufb : buffer backend
  * @offset : offset within the buffer
  * @src : source address
@@ -570,7 +570,7 @@ EXPORT_SYMBOL_GPL(_lib_ring_buffer_memset);
  * directly without having the src pointer checked with access_ok()
  * previously.
  */
-void _lib_ring_buffer_copy_from_user(struct lib_ring_buffer_backend *bufb,
+void _lib_ring_buffer_copy_from_user_inatomic(struct lib_ring_buffer_backend *bufb,
                                      size_t offset,
                                      const void __user *src, size_t len,
                                      ssize_t pagecpy)
@@ -601,7 +601,7 @@ void _lib_ring_buffer_copy_from_user(struct lib_ring_buffer_backend *bufb,
                rpages = bufb->array[sb_bindex];
                CHAN_WARN_ON(chanb, config->mode == RING_BUFFER_OVERWRITE
                                && subbuffer_id_is_noref(config, id));
-               ret = lib_ring_buffer_do_copy_from_user(rpages->p[index].virt
+               ret = lib_ring_buffer_do_copy_from_user_inatomic(rpages->p[index].virt
                                                        + (offset & ~PAGE_MASK),
                                                        src, pagecpy) != 0;
                if (ret > 0) {
@@ -612,7 +612,7 @@ void _lib_ring_buffer_copy_from_user(struct lib_ring_buffer_backend *bufb,
                }
        } while (unlikely(len != pagecpy));
 }
-EXPORT_SYMBOL_GPL(_lib_ring_buffer_copy_from_user);
+EXPORT_SYMBOL_GPL(_lib_ring_buffer_copy_from_user_inatomic);
 
 /**
  * lib_ring_buffer_read - read data from ring_buffer_buffer.
@@ -724,8 +724,9 @@ EXPORT_SYMBOL_GPL(__lib_ring_buffer_copy_to_user);
  * @dest : destination address
  * @len : destination's length
  *
- * return string's length
+ * Return string's length, or -EINVAL on error.
  * Should be protected by get_subbuf/put_subbuf.
+ * Destination length should be at least 1 to hold '\0'.
  */
 int lib_ring_buffer_read_cstr(struct lib_ring_buffer_backend *bufb, size_t offset,
                              void *dest, size_t len)
@@ -741,6 +742,8 @@ int lib_ring_buffer_read_cstr(struct lib_ring_buffer_backend *bufb, size_t offse
        offset &= chanb->buf_size - 1;
        index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT;
        orig_offset = offset;
+       if (unlikely(!len))
+               return -EINVAL;
        for (;;) {
                id = bufb->buf_rsb.id;
                sb_bindex = subbuffer_id_get_index(config, id);