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MDEV-22387: Do not pass null pointer to some memcpy()

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Passing a null pointer to a nonnull argument is not only undefined
behaviour, but it also grants the compiler the permission to optimize
away further checks whether the pointer is null. GCC -O2 at least
starting with version 8 may do that, potentially causing SIGSEGV.

These problems were caught in a WITH_UBSAN=ON build with the
Bug#7024 test in main.view.
This commit is contained in:
Marko Mäkelä
2020-09-03 09:05:56 +03:00
parent a256070e7d
commit 94a520ddbe
5 changed files with 17 additions and 9 deletions
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5
sql/sql_string.h
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@@ -3,7 +3,7 @@
/*
Copyright (c) 2000, 2013, Oracle and/or its affiliates.
Copyright (c) 2008, 2013, Monty Program Ab.
Copyright (c) 2008, 2020, MariaDB Corporation.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
@@ -512,7 +512,8 @@ public:
}
void q_append(const char *data, uint32 data_len)
{
memcpy(Ptr + str_length, data, data_len);
if (data_len)
memcpy(Ptr + str_length, data, data_len);
str_length += data_len;
}