tree 24c7af72900b480ec80f1b0554fd905ced379b15
parent 76837bc948578e91e113141bd4c73dad8093be3b
author Tim Duesterhus <tim@bastelstu.be> 1610098533 +0100
committer Willy Tarreau <w@1wt.eu> 1610113603 +0100
encoding latin1

BUG/MINOR: hlua: Fix memory leak in hlua_alloc

During a configuration check valgrind reports:

    ==14425== 0 bytes in 106 blocks are definitely lost in loss record 1 of 107
    ==14425==    at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
    ==14425==    by 0x4C2FDEF: realloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
    ==14425==    by 0x443CFC: hlua_alloc (hlua.c:8662)
    ==14425==    by 0x5F72B11: luaM_realloc_ (in /usr/lib/x86_64-linux-gnu/liblua5.3.so.0.0.0)
    ==14425==    by 0x5F78089: luaH_free (in /usr/lib/x86_64-linux-gnu/liblua5.3.so.0.0.0)
    ==14425==    by 0x5F707D3: sweeplist (in /usr/lib/x86_64-linux-gnu/liblua5.3.so.0.0.0)
    ==14425==    by 0x5F710D0: luaC_freeallobjects (in /usr/lib/x86_64-linux-gnu/liblua5.3.so.0.0.0)
    ==14425==    by 0x5F7715D: close_state (in /usr/lib/x86_64-linux-gnu/liblua5.3.so.0.0.0)
    ==14425==    by 0x443D4C: hlua_deinit (hlua.c:9302)
    ==14425==    by 0x543F88: deinit (haproxy.c:2742)
    ==14425==    by 0x5448E7: deinit_and_exit (haproxy.c:2830)
    ==14425==    by 0x5455D9: init (haproxy.c:2044)

This is due to Lua calling `hlua_alloc()` with `ptr = NULL` and `nsize = 0`.
While `realloc` is supposed to be equivalent `free()` if the size is `0` this
is only required for a non-NULL pointer. Apparently my allocator (or valgrind)
actually allocates a zero size area if the pointer is NULL, possibly taking up
some memory for management structures.

Fix this leak by specifically handling the case where both the pointer and the
size are `0`.

This bug appears to have been introduced with the introduction of the
multi-threaded Lua, thus this fix is specific for 2.4. No backport needed.