Fix: refuse overwrite mode buffers with less than two subbuffers

[lttng-ust.git] / libringbuffer / ring_buffer_backend.c

diff --git a/libringbuffer/ring_buffer_backend.c b/libringbuffer/ring_buffer_backend.c
index e949a5e292d2048f306760f329f64d668a0c30cd..7d3a37809e73da27b25d43d8914ed285545075f7 100644 (file)
--- a/libringbuffer/ring_buffer_backend.c
+++ b/libringbuffer/ring_buffer_backend.c
@@ -1,9 +1,21 @@
 /*
  * ring_buffer_backend.c
  *
- * Copyright (C) 2005-2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  *
- * Dual LGPL v2.1/GPL v2 license.
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; only
+ * version 2.1 of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #define _GNU_SOURCE
@@ -210,9 +222,6 @@ int channel_backend_init(struct channel_backend *chanb,
        if (!name)
                return -EPERM;
 
-       if (!(subbuf_size && num_subbuf))
-               return -EPERM;
-
        /* Check that the subbuffer size is larger than a page. */
        if (subbuf_size < PAGE_SIZE)
                return -EINVAL;
@@ -225,6 +234,12 @@ int channel_backend_init(struct channel_backend *chanb,
                return -EINVAL;
        if (!num_subbuf || (num_subbuf & (num_subbuf - 1)))
                return -EINVAL;
+       /*
+        * Overwrite mode buffers require at least 2 subbuffers per
+        * buffer.
+        */
+       if (config->mode == RING_BUFFER_OVERWRITE && num_subbuf < 2)
+               return -EINVAL;
 
        ret = subbuffer_id_check_index(config, num_subbuf);
        if (ret)
@@ -271,7 +286,8 @@ int channel_backend_init(struct channel_backend *chanb,
                for_each_possible_cpu(i) {
                        struct shm_object *shmobj;
 
-                       shmobj = shm_object_table_append(handle->table, shmsize);
+                       shmobj = shm_object_table_alloc(handle->table, shmsize,
+                                       SHM_OBJECT_SHM);
                        if (!shmobj)
                                goto end;
                        align_shm(shmobj, __alignof__(struct lttng_ust_lib_ring_buffer));
@@ -289,7 +305,8 @@ int channel_backend_init(struct channel_backend *chanb,
                struct shm_object *shmobj;
                struct lttng_ust_lib_ring_buffer *buf;
 
-               shmobj = shm_object_table_append(handle->table, shmsize);
+               shmobj = shm_object_table_alloc(handle->table, shmsize,
+                                       SHM_OBJECT_SHM);
                if (!shmobj)
                        goto end;
                align_shm(shmobj, __alignof__(struct lttng_ust_lib_ring_buffer));
@@ -370,8 +387,9 @@ size_t lib_ring_buffer_read(struct lttng_ust_lib_ring_buffer_backend *bufb, size
  * @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 lttng_ust_lib_ring_buffer_backend *bufb, size_t offset,
                              void *dest, size_t len, struct lttng_ust_shm_handle *handle)
@@ -383,6 +401,8 @@ int lib_ring_buffer_read_cstr(struct lttng_ust_lib_ring_buffer_backend *bufb, si
        struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
        unsigned long sb_bindex, id;
 
+       if (caa_unlikely(!len))
+               return -EINVAL;
        offset &= chanb->buf_size - 1;
        orig_offset = offset;
        id = bufb->buf_rsb.id;
@@ -411,8 +431,9 @@ int lib_ring_buffer_read_cstr(struct lttng_ust_lib_ring_buffer_backend *bufb, si
  *
  * Return the address where a given offset is located (for read).
  * Should be used to get the current subbuffer header pointer. Given we know
- * it's never on a page boundary, it's safe to write directly to this address,
- * as long as the write is never bigger than a page size.
+ * it's never on a page boundary, it's safe to read/write directly
+ * from/to this address, as long as the read/write is never bigger than
+ * a page size.
  */
 void *lib_ring_buffer_read_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb,
                                          size_t offset,