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bug: Metatable may access its own dealocated field when 

it has a self reference in __newindex + some refactoring
This commit is contained in:
Roberto Ierusalimschy 2016-01-04 14:44:50 -02:00
parent b12b635a90
commit a272fa66f0
1 changed files with 22 additions and 21 deletions
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43
lvm.c
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@ -1,5 +1,5 @@
/* /*
** $Id: lvm.c,v 2.264 2015/11/19 19:16:22 roberto Exp roberto $ ** $Id: lvm.c,v 2.265 2015/11/23 11:30:45 roberto Exp roberto $
** Lua virtual machine ** Lua virtual machine
** See Copyright Notice in lua.h ** See Copyright Notice in lua.h
*/ */
@ -153,7 +153,7 @@ static int forlimit (const TValue *obj, lua_Integer *p, lua_Integer step,
/* /*
** Complete a table access: if 't' is a table, 'tm' has its metamethod; ** Finish a table access: if 't' is a table, 'tm' has its metamethod;
** otherwise, 'tm' is NULL. ** otherwise, 'tm' is NULL.
*/ */
void luaV_finishget (lua_State *L, const TValue *t, TValue *key, StkId val, void luaV_finishget (lua_State *L, const TValue *t, TValue *key, StkId val,
@ -176,32 +176,33 @@ void luaV_finishget (lua_State *L, const TValue *t, TValue *key, StkId val,
} }
/* else repeat */ /* else repeat */
} }
luaG_runerror(L, "gettable chain too long; possible loop"); luaG_runerror(L, "'__index' chain too long; possible loop");
} }
/* /*
** Main function for table assignment (invoking metamethods if needed). ** Finish a table assignment 't[key] = val'.
** Compute 't[key] = val' ** If 'oldval' is NULL, 't' is not a table. Otherwise, 'oldval' points
** to the entry 't[key]', or to 'luaO_nilobject' if there is no such
** entry. (The value at 'oldval' must be nil, otherwise 'luaV_fastset'
** would have done the job.)
*/ */
void luaV_finishset (lua_State *L, const TValue *t, TValue *key, void luaV_finishset (lua_State *L, const TValue *t, TValue *key,
StkId val, const TValue *oldval) { StkId val, const TValue *oldval) {
int loop; /* counter to avoid infinite loops */ int loop; /* counter to avoid infinite loops */
for (loop = 0; loop < MAXTAGLOOP; loop++) { for (loop = 0; loop < MAXTAGLOOP; loop++) {
const TValue *tm; const TValue *tm; /* '__newindex' metamethod */
if (oldval != NULL) { if (oldval != NULL) { /* is 't' a table? */
lua_assert(ttistable(t) && ttisnil(oldval)); Table *h = hvalue(t); /* save 't' table */
/* must check the metamethod */ lua_assert(ttisnil(oldval)); /* old value must be nil */
if ((tm = fasttm(L, hvalue(t)->metatable, TM_NEWINDEX)) == NULL && tm = fasttm(L, h->metatable, TM_NEWINDEX); /* get metamethod */
/* no metamethod; is there a previous entry in the table? */ if (tm == NULL) { /* no metamethod? */
(oldval != luaO_nilobject || if (oldval == luaO_nilobject) /* no previous entry? */
/* no previous entry; must create one. (The next test is oldval = luaH_newkey(L, h, key); /* create one */
always true; we only need the assignment.) */
(oldval = luaH_newkey(L, hvalue(t), key), 1))) {
/* no metamethod and (now) there is an entry with given key */ /* no metamethod and (now) there is an entry with given key */
setobj2t(L, cast(TValue *, oldval), val); setobj2t(L, cast(TValue *, oldval), val); /* set its new value */
invalidateTMcache(hvalue(t)); invalidateTMcache(h);
luaC_barrierback(L, hvalue(t), val); luaC_barrierback(L, h, val);
return; return;
} }
/* else will try the metamethod */ /* else will try the metamethod */
@ -220,7 +221,7 @@ void luaV_finishset (lua_State *L, const TValue *t, TValue *key,
return; /* done */ return; /* done */
/* else loop */ /* else loop */
} }
luaG_runerror(L, "settable chain too long; possible loop"); luaG_runerror(L, "'__newindex' chain too long; possible loop");
} }
@ -744,8 +745,8 @@ void luaV_finishOp (lua_State *L) {
/* /*
** copy of 'luaV_gettable', but protecting call to potential metamethod ** copy of 'luaV_gettable', but protecting the call to potential
** (which can reallocate the stack) ** metamethod (which can reallocate the stack)
*/ */
#define gettableProtected(L,t,k,v) { const TValue *aux; \ #define gettableProtected(L,t,k,v) { const TValue *aux; \
if (luaV_fastget(L,t,k,aux,luaH_get)) { setobj2s(L, v, aux); } \ if (luaV_fastget(L,t,k,aux,luaH_get)) { setobj2s(L, v, aux); } \