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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.
This commit is contained in:
Tim Duesterhus 2021-01-08 10:35:33 +01:00 committed by Willy Tarreau
parent 76837bc948
commit 22586524e3
1 changed files with 3 additions and 0 deletions
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3
src/hlua.c
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@ -8640,6 +8640,9 @@ static void *hlua_alloc(void *ud, void *ptr, size_t osize, size_t nsize)
struct hlua_mem_allocator *zone = ud;
size_t limit, old, new;
if (unlikely(!ptr && !nsize))
return NULL;
/* a limit of ~0 means unlimited and boot complete, so there's no need
* for accounting anymore.
*/