From: Timo Sirainen <timo.sirainen@open-xchange.com>
Date: Wed, 31 Mar 2021 11:40:12 +0000 (+0300)
Subject: lib: t_get_bytes_available() - Fix return value when current_block is almost full
X-Git-Tag: 2.3.16~244
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=aff92930fb16f4158e086af7ac7248e84019d23d;p=thirdparty%2Fdovecot%2Fcore.git

lib: t_get_bytes_available() - Fix return value when current_block is almost full
---

diff --git a/src/lib/data-stack.c b/src/lib/data-stack.c
index 756e856fc2..201296e30b 100644
--- a/src/lib/data-stack.c
+++ b/src/lib/data-stack.c
@@ -534,15 +534,17 @@ t_try_realloc(void *mem, size_t size)
 
 size_t t_get_bytes_available(void)
 {
+	block_canary_check(current_block);
 #ifndef DEBUG
-	const unsigned int extra = MEM_ALIGN_SIZE-1;
+	const unsigned int min_extra = 0;
 #else
-	const unsigned int extra = MEM_ALIGN_SIZE-1 + SENTRY_COUNT +
-		MEM_ALIGN(sizeof(size_t));
+	const unsigned int min_extra = SENTRY_COUNT + MEM_ALIGN(sizeof(size_t));
 #endif
-	block_canary_check(current_block);
-	return current_block->left < extra ? current_block->left :
-		current_block->left - extra;
+	if (current_block->left < min_extra)
+		return 0;
+	size_t size = current_block->left - min_extra;
+	i_assert(ALLOC_SIZE(size) == current_block->left);
+	return size;
 }
 
 void *t_buffer_get(size_t size)
diff --git a/src/lib/test-data-stack.c b/src/lib/test-data-stack.c
index 34fc4fcad6..c6f22a51cb 100644
--- a/src/lib/test-data-stack.c
+++ b/src/lib/test-data-stack.c
@@ -3,6 +3,34 @@
 #include "test-lib.h"
 #include "data-stack.h"
 
+static void test_ds_get_bytes_available(void)
+{
+	test_begin("data-stack t_get_bytes_available()");
+	for (unsigned int i = 0; i < 32; i++) {
+		size_t orig_avail = t_get_bytes_available();
+		size_t avail1;
+		T_BEGIN {
+			if (i > 0)
+				t_malloc_no0(i);
+			avail1 = t_get_bytes_available();
+			t_malloc_no0(avail1);
+			test_assert_idx(t_get_bytes_available() == 0, i);
+			t_malloc_no0(1);
+			test_assert_idx(t_get_bytes_available() > 0, i);
+		} T_END;
+		T_BEGIN {
+			if (i > 0)
+				t_malloc_no0(i);
+			size_t avail2 = t_get_bytes_available();
+			test_assert_idx(avail1 == avail2, i);
+			t_malloc_no0(avail2 + 1);
+			test_assert_idx(t_get_bytes_available() > 0, i);
+		} T_END;
+		test_assert_idx(t_get_bytes_available() == orig_avail, i);
+	}
+	test_end();
+}
+
 static void test_ds_buffers(void)
 {
 	test_begin("data-stack buffer growth");
@@ -11,7 +39,7 @@ static void test_ds_buffers(void)
 		unsigned char *p;
 		size_t left = t_get_bytes_available();
 		while (left < 10000) {
-			t_malloc_no0(left); /* force a new block */
+			t_malloc_no0(left+1); /* force a new block */
 			left = t_get_bytes_available();
 		}
 		left -= 64; /* make room for the sentry if DEBUG */
@@ -70,7 +98,7 @@ static void test_ds_realloc()
 		unsigned char *p;
 		size_t left = t_get_bytes_available();
 		while (left < 10000) {
-			t_malloc_no0(left); /* force a new block */
+			t_malloc_no0(left+1); /* force a new block */
 			left = t_get_bytes_available();
 		}
 		left -= 64; /* make room for the sentry if DEBUG */
@@ -207,6 +235,7 @@ static void test_ds_pass_str(void)
 
 void test_data_stack(void)
 {
+	test_ds_get_bytes_available();
 	test_ds_buffers();
 	test_ds_realloc();
 	test_ds_recursive(20, 80);