Use dummy allocator to make accesses defined as per standard (#11982)

## Issue
When we use GCC-12 later or clang 9.0 later to build with `-D_FORTIFY_SOURCE=3`,
we can see the following buffer overflow:
```
=== REDIS BUG REPORT START: Cut & paste starting from here ===
6263:M 06 Apr 2023 08:59:12.915 # Redis 255.255.255 crashed by signal: 6, si_code: -6
6263:M 06 Apr 2023 08:59:12.915 # Crashed running the instruction at: 0x7f03d59efa7c

------ STACK TRACE ------
EIP:
/lib/x86_64-linux-gnu/libc.so.6(pthread_kill+0x12c)[0x7f03d59efa7c]

Backtrace:
/lib/x86_64-linux-gnu/libc.so.6(+0x42520)[0x7f03d599b520]
/lib/x86_64-linux-gnu/libc.so.6(pthread_kill+0x12c)[0x7f03d59efa7c]
/lib/x86_64-linux-gnu/libc.so.6(raise+0x16)[0x7f03d599b476]
/lib/x86_64-linux-gnu/libc.so.6(abort+0xd3)[0x7f03d59817f3]
/lib/x86_64-linux-gnu/libc.so.6(+0x896f6)[0x7f03d59e26f6]
/lib/x86_64-linux-gnu/libc.so.6(__fortify_fail+0x2a)[0x7f03d5a8f76a]
/lib/x86_64-linux-gnu/libc.so.6(+0x1350c6)[0x7f03d5a8e0c6]
src/redis-server 127.0.0.1:25111(+0xd5e80)[0x557cddd3be80]
src/redis-server 127.0.0.1:25111(feedReplicationBufferWithObject+0x78)[0x557cddd3c768]
src/redis-server 127.0.0.1:25111(replicationFeedSlaves+0x1a4)[0x557cddd3cbc4]
src/redis-server 127.0.0.1:25111(+0x8721a)[0x557cddced21a]
src/redis-server 127.0.0.1:25111(call+0x47a)[0x557cddcf38ea]
src/redis-server 127.0.0.1:25111(processCommand+0xbf4)[0x557cddcf4aa4]
src/redis-server 127.0.0.1:25111(processInputBuffer+0xe6)[0x557cddd22216]
src/redis-server 127.0.0.1:25111(readQueryFromClient+0x3a8)[0x557cddd22898]
src/redis-server 127.0.0.1:25111(+0x1b9134)[0x557cdde1f134]
src/redis-server 127.0.0.1:25111(aeMain+0x119)[0x557cddce5349]
src/redis-server 127.0.0.1:25111(main+0x466)[0x557cddcd6716]
/lib/x86_64-linux-gnu/libc.so.6(+0x29d90)[0x7f03d5982d90]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x80)[0x7f03d5982e40]
src/redis-server 127.0.0.1:25111(_start+0x25)[0x557cddcd7025]
```

The main reason is that when FORTIFY_SOURCE is enabled, GCC or clang will enhance some
common functions, such as `strcpy`, `memcpy`, `fgets`, etc, so that they can detect buffer
overflow errors and stop program execution, thus improving the safety of the program.
We use `zmalloc_usable_size()` everywhere to use memory blocks, but that is an abuse since the
malloc_usable_size() isn't meant for this kind of use, it is for diagnostics only. That is also why the
behavior is flaky when built with _FORTIFY_SOURCE, the compiler can sense that we reach outside
the allocated block and SIGABRT.

### Solution
If we need to use the additional memory we got, we need to use a dummy realloc with `alloc_size` attribute
and no inlining, (see `extend_to_usable`) to let the compiler see the large of memory we need to use.
This can either be an implicit call inside `z*usable` that returns the size, so that the caller doesn't have any
other worry, or it can be a normal zmalloc call which means that if the caller wants to use
zmalloc_usable_size it must also use extend_to_usable.

### Changes

This PR does the following:
1) rename the current z[try]malloc_usable family to z[try]malloc_internal and don't expose them to users outside zmalloc.c,
2) expose a new set of `z[*]_usable` family that use z[*]_internal and `extend_to_usable()` implicitly, the caller gets the
  size of the allocation and it is safe to use.
3) go over all the users of `zmalloc_usable_size` and convert them to use the `z[*]_usable` family if possible.
4) in the places where the caller can't use `z[*]_usable` and store the real size, and must still rely on zmalloc_usable_size,
  we still make sure that the allocation used `z[*]_usable` (which has a call to `extend_to_usable()`) and ignores the
  returning size, this way a later call to `zmalloc_usable_size` is still safe.

[4] was done for module.c and listpack.c, all the others places (sds, reply proto list, replication backlog, client->buf)
are using [3].

Co-authored-by: Oran Agra <oran@redislabs.com>

1 files changed, 14 insertions, 4 deletions

diff --git a/src/module.c b/src/module.c
index ae75b3dc2..e29277956 100644
--- a/src/module.c
+++ b/src/module.c
@@ -516,13 +516,20 @@ void moduleCreateContext(RedisModuleCtx *out_ctx, RedisModule *module, int ctx_f
  * You should avoid using malloc().
  * This function panics if unable to allocate enough memory. */
 void *RM_Alloc(size_t bytes) {
-    return zmalloc(bytes);
+    /* Use 'zmalloc_usable()' instead of 'zmalloc()' to allow the compiler
+     * to recognize the additional memory size, which means that modules can
+     * use the memory reported by 'RM_MallocUsableSize()' safely. In theory this
+     * isn't really needed since this API can't be inlined (not even for embedded
+     * modules like TLS (we use function pointers for module APIs), and the API doesn't
+     * have the malloc_size attribute, but it's hard to predict how smart future compilers
+     * will be, so better safe than sorry. */
+    return zmalloc_usable(bytes,NULL);
 }
 
 /* Similar to RM_Alloc, but returns NULL in case of allocation failure, instead
  * of panicking. */
 void *RM_TryAlloc(size_t bytes) {
-    return ztrymalloc(bytes);
+    return ztrymalloc_usable(bytes,NULL);
 }
 
 /* Use like calloc(). Memory allocated with this function is reported in
@@ -530,12 +537,12 @@ void *RM_TryAlloc(size_t bytes) {
  * and in general is taken into account as memory allocated by Redis.
  * You should avoid using calloc() directly. */
 void *RM_Calloc(size_t nmemb, size_t size) {
-    return zcalloc(nmemb*size);
+    return zcalloc_usable(nmemb*size,NULL);
 }
 
 /* Use like realloc() for memory obtained with RedisModule_Alloc(). */
 void* RM_Realloc(void *ptr, size_t bytes) {
-    return zrealloc(ptr,bytes);
+    return zrealloc_usable(ptr,bytes,NULL);
 }
 
 /* Use like free() for memory obtained by RedisModule_Alloc() and
@@ -10704,6 +10711,9 @@ size_t RM_MallocSize(void* ptr) {
 /* Similar to RM_MallocSize, the difference is that RM_MallocUsableSize
  * returns the usable size of memory by the module. */
 size_t RM_MallocUsableSize(void *ptr) {
+    /* It is safe to use 'zmalloc_usable_size()' to manipulate additional
+     * memory space, as we guarantee that the compiler can recognize this
+     * after 'RM_Alloc', 'RM_TryAlloc', 'RM_Realloc', or 'RM_Calloc'. */
     return zmalloc_usable_size(ptr);
 }