MINOR: shctx: add a few BUG_ON() for consistency checks

The shctx code relies on sensitive conditions that are hard to infer
from the code itself, let's add some BUG_ON() to verify them. They
helped spot the previous bugs.

(cherry picked from commit 48b608026b7c0d55a55b9746179542c7d524e84a)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit f7ea50931909ccb3df939ab7ff1b1e5c24c295ce)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>

diff --git a/src/shctx.c b/src/shctx.c
index 02486f4..5a546f7 100644 (file)
--- a/src/shctx.c
+++ b/src/shctx.c
@@ -34,6 +34,8 @@ struct shared_block *shctx_row_reserve_hot(struct shared_context *shctx,
        int freed = 0;
        int remain;
 
+       BUG_ON(data_len < 0);
+
        /* not enough usable blocks */
        if (data_len > shctx->nbav * shctx->block_size)
                goto out;
@@ -93,6 +95,8 @@ struct shared_block *shctx_row_reserve_hot(struct shared_context *shctx,
                        block->len = 0;
 
                        freed++;
+
+                       BUG_ON(data_len < 0);
                        data_len -= shctx->block_size;
 
                        if (data_len > 0 || !enough) {
@@ -213,6 +217,8 @@ int shctx_row_data_append(struct shared_context *shctx,
 
                /* remaining written bytes in the current block. */
                remain = (shctx->block_size * first->block_count - first->len) % shctx->block_size;
+               BUG_ON(remain < 0);
+
                /* if remain == 0, previous buffers are full, or first->len == 0 */
                if (!remain) {
                        remain = shctx->block_size;
@@ -221,6 +227,7 @@ int shctx_row_data_append(struct shared_context *shctx,
                else {
                        /* start must be calculated before remain is modified */
                        start = shctx->block_size - remain;
+                       BUG_ON(start < 0);
                }
 
                /* must not try to copy more than len */
@@ -270,8 +277,11 @@ int shctx_row_data_get(struct shared_context *shctx, struct shared_block *first,
                if (start == -1)
                        start = offset - (count - 1) * shctx->block_size;
 
+               BUG_ON(start < 0);
+
                /* size can be lower than a block when copying the last block */
                size = MIN(shctx->block_size - start, len);
+               BUG_ON(size < 0);
 
                memcpy(dst, block->data + start, size);
                dst += size;