## 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>
Avoid repeated reallocs growing the listpack while entries are being added.
This is done by pre-allocating the listpack to near maximum size, and using
malloc_size to check if it needs realloc or not.
When the listpack reaches the maximum number of entries, we shrink it to fit it's used size.
Co-authored-by: Viktor Söderqvist <viktor@zuiderkwast.se>
Co-authored-by: Oran Agra <oran@redislabs.com>
Pieter Cailliau