Fix: handle writes of length 0

[lttng-modules.git] / lib / ringbuffer / backend.h

diff --git a/lib/ringbuffer/backend.h b/lib/ringbuffer/backend.h
index ed913325e2ddb70070392226cc9b27b39df18fad..bbbc80d8eb03be444d4890d828d92f7f6eb118ab 100644 (file)
--- a/lib/ringbuffer/backend.h
+++ b/lib/ringbuffer/backend.h
@@ -96,6 +96,8 @@ void lib_ring_buffer_write(const struct lib_ring_buffer_config *config,
        struct lib_ring_buffer_backend_pages *rpages;
        unsigned long sb_bindex, id;
 
+       if (unlikely(!len))
+               return;
        offset &= chanb->buf_size - 1;
        sbidx = offset >> chanb->subbuf_size_order;
        index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT;
@@ -142,6 +144,8 @@ void lib_ring_buffer_memset(const struct lib_ring_buffer_config *config,
        struct lib_ring_buffer_backend_pages *rpages;
        unsigned long sb_bindex, id;
 
+       if (unlikely(!len))
+               return;
        offset &= chanb->buf_size - 1;
        sbidx = offset >> chanb->subbuf_size_order;
        index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT;
@@ -189,6 +193,8 @@ void lib_ring_buffer_copy_from_user_inatomic(const struct lib_ring_buffer_config
        unsigned long ret;
        mm_segment_t old_fs = get_fs();
 
+       if (unlikely(!len))
+               return;
        offset &= chanb->buf_size - 1;
        sbidx = offset >> chanb->subbuf_size_order;
        index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT;