Memory leaks in Lua: luaL_addgsub, luaL_gsub, luaL_loadbuffer

[ligurio]

Initially reported in #25 and oss-fuzz#58707.

How to reproduce

CC=clang CXX=clang++ cmake -S . -B build -DCMAKE_BUILD_TYPE=Debug -DUSE_LUA=ON
cmake --build build --parallel

luaL_addgsub_test:

./build/tests/luaL_addgsub_test
<snipped>
Indirect leak of 29 byte(s) in 1 object(s) allocated from:                                                                                  
    #0 0x559bc122c995 in realloc (/home/sergeyb/sources/lua-c-api-tests/build/tests/luaL_addgsub_test+0x145995) (BuildId: e31da1e432417eded9
ddb02691e605f88d0d01ad)                                                                                                                     
    #1 0x559bc13749bd in l_alloc /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lauxlib.c:1024:12
    #2 0x559bc12db3bb in luaM_malloc_ /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lmem.c:206:22                           
    #3 0x559bc12c1b83 in luaC_newobjdt /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lgc.c:260:13                           
    #4 0x559bc12c1de4 in luaC_newobj /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lgc.c:271:10
    #5 0x559bc1303550 in createstrobj /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lstring.c:148:7
    #6 0x559bc130442c in internshrstr /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lstring.c:208:8
    #7 0x559bc13032a2 in luaS_newlstr /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lstring.c:223:12
    #8 0x559bc138cdc3 in luaX_init /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/llex.c:72:16
    #9 0x559bc12fff6d in f_luaopen /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lstate.c:238:3
    #10 0x559bc12a786e in luaD_rawrunprotected /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/ldo.c:144:3
    #11 0x559bc12ff9aa in lua_newstate /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lstate.c:407:7
    #12 0x559bc137486f in luaL_newstate /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lauxlib.c:1095:18
    #13 0x559bc126b2f2 in LLVMFuzzerTestOneInput /home/sergeyb/sources/lua-c-api-tests/tests/luaL_addgsub_test.cc:25:17

<snipped>

Indirect leak of 32 byte(s) in 1 object(s) allocated from:                                                                                  
    #0 0x559bc122c995 in realloc (/home/sergeyb/sources/lua-c-api-tests/build/tests/luaL_addgsub_test+0x145995) (BuildId: e31da1e432417eded9
ddb02691e605f88d0d01ad)                                                                                                                     
    #1 0x559bc13749bd in l_alloc /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lauxlib.c:1024:12                            
    #2 0x559bc12dad49 in luaM_realloc_ /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lmem.c:180:14
    #3 0x559bc13075c2 in luaH_resize /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/ltable.c:573:14                          
    #4 0x559bc1301185 in init_registry /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lstate.c:220:3                         
    #5 0x559bc12fff52 in f_luaopen /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lstate.c:235:3
    #6 0x559bc12a786e in luaD_rawrunprotected /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/ldo.c:144:3
    #7 0x559bc12ff9aa in lua_newstate /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lstate.c:407:7 
    #8 0x559bc137486f in luaL_newstate /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lauxlib.c:1095:18
    #9 0x559bc126b2f2 in LLVMFuzzerTestOneInput /home/sergeyb/sources/lua-c-api-tests/tests/luaL_addgsub_test.cc:25:17

<snipped>

luaL_gsub_test:

./build/tests/luaL_gsub_test
<snipped>

Indirect leak of 29 byte(s) in 1 object(s) allocated from:
    #0 0x5614209bd995 in realloc (/home/sergeyb/sources/lua-c-api-tests/build/tests/luaL_gsub_test+0x145995) (BuildId: d5278ec1ec3fad35fd14e
bcd6b99d008099d8855)
    #1 0x561420b058cd in l_alloc /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lauxlib.c:1024:12
    #2 0x561420a6c2cb in luaM_malloc_ /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lmem.c:206:22
    #3 0x561420a52a93 in luaC_newobjdt /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lgc.c:260:13
    #4 0x561420a52cf4 in luaC_newobj /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lgc.c:271:10
    #5 0x561420a94460 in createstrobj /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lstring.c:148:7
    #6 0x561420a9533c in internshrstr /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lstring.c:208:8
    #7 0x561420a941b2 in luaS_newlstr /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lstring.c:223:12
    #8 0x561420b1dcd3 in luaX_init /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/llex.c:72:16
    #9 0x561420a90e7d in f_luaopen /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lstate.c:238:3
    #10 0x561420a3877e in luaD_rawrunprotected /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/ldo.c:144:3
    #11 0x561420a908ba in lua_newstate /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lstate.c:407:7
    #12 0x561420b0577f in luaL_newstate /home/sergeyb/sources/lua-c-api-tests/build/lua-master/source/lauxlib.c:1095:18
    #13 0x5614209fc2f2 in LLVMFuzzerTestOneInput /home/sergeyb/sources/lua-c-api-tests/tests/luaL_gsub_test.cc:25:17

<snipped>

Is it a false positive or not?

[ligurio]

LeakSanitizer temporarily disabled in 98db57a95c9da887941e4eac0c3c00bfda4310ac using .options files.