From: Vincent Pit <vince@profvince.com>
Date: Wed, 26 Oct 2011 17:22:13 +0000 (+0200)
Subject: Enforce saner checks on wizard SVs and MAGIC tokens
X-Git-Tag: v0.47~9
X-Git-Url: http://git.vpit.fr/?p=perl%2Fmodules%2FVariable-Magic.git;a=commitdiff_plain;h=8991ed7c69639359044bebf70ffaf8585b885252

Enforce saner checks on wizard SVs and MAGIC tokens

This commit adds a variety of helper functions that extract the vmg_wizard
object from a SV or a MAGIC token. Version with (for direct interaction
with the user) and without checks (for magic callbacks, where we know the
MAGIC token is already valid) are provided.
---

diff --git a/Magic.xs b/Magic.xs
index 0d17eef..3c4cd33 100644
--- a/Magic.xs
+++ b/Magic.xs
@@ -591,6 +591,8 @@ STATIC const vmg_wizard *vmg_wizard_dup(pTHX_ const vmg_wizard *w, CLONE_PARAMS
 
 #endif /* VMG_THREADSAFE */
 
+#define vmg_wizard_id(W) PTR2IV(vmg_vtable_vtbl((W)->vtable))
+
 /* --- Wizard SV objects --------------------------------------------------- */
 
 STATIC int vmg_wizard_sv_free(pTHX_ SV *sv, MAGIC *mg) {
@@ -652,26 +654,11 @@ STATIC SV *vmg_wizard_sv_new(pTHX_ const vmg_wizard *w) {
  return wiz;
 }
 
-STATIC const SV *vmg_wizard_sv_validate(pTHX_ const SV *wiz) {
-#define vmg_wizard_sv_validate(W) vmg_wizard_sv_validate(aTHX_ (W))
- if (SvROK(wiz)) {
-  wiz = SvRV_const(wiz);
 #if VMG_THREADSAFE
-  if (SvTYPE(wiz) >= SVt_PVMG && SvMAGIC(wiz))
-#else
-  if (SvIOK(wiz))
-#endif
-   return wiz;
- }
-
- croak(vmg_invalid_wiz);
- /* Not reached */
- return NULL;
-}
 
-#if VMG_THREADSAFE
+#define vmg_sv_has_wizard_type(S) (SvTYPE(S) >= SVt_PVMG)
 
-STATIC const vmg_wizard *vmg_wizard_from_sv(const SV *wiz) {
+STATIC const vmg_wizard *vmg_wizard_from_sv_nocheck(const SV *wiz) {
  MAGIC *mg;
 
  for (mg = SvMAGIC(wiz); mg; mg = mg->mg_moremagic) {
@@ -682,35 +669,45 @@ STATIC const vmg_wizard *vmg_wizard_from_sv(const SV *wiz) {
  return NULL;
 }
 
-#define vmg_wizard_from_sv(W) vmg_wizard_from_sv((const SV *) (W))
+#else /* VMG_THREADSAFE */
 
-#define vmg_wizard_sv_id(W) PTR2IV(vmg_vtable_vtbl(vmg_wizard_from_sv(W)->vtable))
+#define vmg_sv_has_wizard_type(S) SvIOK(S)
 
-#else
+#define vmg_wizard_from_sv_nocheck(W) INT2PTR(const vmg_wizard *, SvIVX(W))
 
-#define vmg_wizard_sv_id(W) SvIVX((const SV *) (W))
+#endif /* !VMG_THREADSAFE */
 
-#define vmg_wizard_from_sv(W) INT2PTR(const vmg_wizard *, vmg_wizard_sv_id(W))
+#define vmg_wizard_from_sv(W) (vmg_sv_has_wizard_type(W) ? vmg_wizard_from_sv_nocheck(W) : NULL)
 
-#endif
+STATIC const vmg_wizard *vmg_wizard_from_mg(const MAGIC *mg) {
+ if (mg->mg_type == PERL_MAGIC_ext && mg->mg_len == HEf_SVKEY) {
+  SV *sv = (SV *) mg->mg_ptr;
+
+  if (vmg_sv_has_wizard_type(sv))
+   return vmg_wizard_from_sv_nocheck(sv);
+ }
+
+ return NULL;
+}
+
+#define vmg_wizard_from_mg_nocheck(M) vmg_wizard_from_sv_nocheck((const SV *) (M)->mg_ptr)
 
 /* --- User-level functions implementation --------------------------------- */
 
-STATIC const MAGIC *vmg_find(const SV *sv, const SV *wiz) {
- const MAGIC *mg, *moremagic;
+STATIC const MAGIC *vmg_find(const SV *sv, const vmg_wizard *w) {
+ const MAGIC *mg;
  IV wid;
 
  if (SvTYPE(sv) < SVt_PVMG)
   return NULL;
 
- wid = vmg_wizard_sv_id(wiz);
- for (mg = SvMAGIC(sv); mg; mg = moremagic) {
-  moremagic = mg->mg_moremagic;
-  if (mg->mg_type == PERL_MAGIC_ext && mg->mg_private == SIG_WIZ) {
-   IV zid = vmg_wizard_sv_id(mg->mg_ptr);
-   if (zid == wid)
-    return mg;
-  }
+ wid = vmg_wizard_id(w);
+
+ for (mg = SvMAGIC(sv); mg; mg = mg->mg_moremagic) {
+  const vmg_wizard *z = vmg_wizard_from_mg(mg);
+
+  if (z && vmg_wizard_id(z) == wid)
+   return mg;
  }
 
  return NULL;
@@ -752,9 +749,10 @@ STATIC SV *vmg_data_new(pTHX_ SV *ctor, SV *sv, SV **args, I32 items) {
  return nsv;
 }
 
-STATIC SV *vmg_data_get(pTHX_ SV *sv, const SV *wiz) {
+STATIC SV *vmg_data_get(pTHX_ SV *sv, const vmg_wizard *w) {
 #define vmg_data_get(S, W) vmg_data_get(aTHX_ (S), (W))
- const MAGIC *mg = vmg_find(sv, wiz);
+ const MAGIC *mg = vmg_find(sv, w);
+
  return mg ? mg->mg_obj : NULL;
 }
 
@@ -775,17 +773,15 @@ STATIC void vmg_uvar_del(SV *sv, MAGIC *prevmagic, MAGIC *mg, MAGIC *moremagic)
 }
 #endif /* VMG_UVAR */
 
-STATIC UV vmg_cast(pTHX_ SV *sv, const SV *wiz, SV **args, I32 items) {
-#define vmg_cast(S, W, A, I) vmg_cast(aTHX_ (S), (W), (A), (I))
- const vmg_wizard *w;
+STATIC UV vmg_cast(pTHX_ SV *sv, const vmg_wizard *w, const SV *wiz, SV **args, I32 items) {
+#define vmg_cast(S, W, WIZ, A, I) vmg_cast(aTHX_ (S), (W), (WIZ), (A), (I))
  MAGIC *mg;
  SV    *data;
  U32    oldgmg;
 
- if (vmg_find(sv, wiz))
+ if (vmg_find(sv, w))
   return 1;
 
- w = vmg_wizard_from_sv(wiz);
  oldgmg = SvGMAGICAL(sv);
 
  data = (w->cb_data) ? vmg_data_new(w->cb_data, sv, args, items) : NULL;
@@ -859,36 +855,39 @@ done:
  return 1;
 }
 
-STATIC UV vmg_dispell(pTHX_ SV *sv, const SV *wiz) {
+STATIC UV vmg_dispell(pTHX_ SV *sv, const vmg_wizard *w) {
 #define vmg_dispell(S, W) vmg_dispell(aTHX_ (S), (W))
 #if VMG_UVAR
  U32 uvars = 0;
 #endif /* VMG_UVAR */
  MAGIC *mg, *prevmagic, *moremagic = NULL;
- IV wid = vmg_wizard_sv_id(wiz);
+ IV wid = vmg_wizard_id(w);
 
  if (SvTYPE(sv) < SVt_PVMG)
   return 0;
 
  for (prevmagic = NULL, mg = SvMAGIC(sv); mg; prevmagic = mg, mg = moremagic) {
+  const vmg_wizard *z;
+
   moremagic = mg->mg_moremagic;
-  if (mg->mg_type == PERL_MAGIC_ext && mg->mg_private == SIG_WIZ) {
+
+  z = vmg_wizard_from_mg(mg);
+  if (z) {
+   IV zid = vmg_wizard_id(z);
+
 #if VMG_UVAR
-   const vmg_wizard *z = vmg_wizard_from_sv(mg->mg_ptr);
-#endif /* VMG_UVAR */
-   IV zid = vmg_wizard_sv_id(mg->mg_ptr);
    if (zid == wid) {
-#if VMG_UVAR
     /* If the current has no uvar, short-circuit uvar deletion. */
     uvars = z->uvar ? (uvars + 1) : 0;
-#endif /* VMG_UVAR */
     break;
-#if VMG_UVAR
    } else if (z->uvar) {
     ++uvars;
     /* We can't break here since we need to find the ext magic to delete. */
-#endif /* VMG_UVAR */
    }
+#else /* VMG_UVAR */
+   if (zid == wid)
+    break;
+#endif /* !VMG_UVAR */
   }
  }
  if (!mg)
@@ -913,12 +912,11 @@ STATIC UV vmg_dispell(pTHX_ SV *sv, const SV *wiz) {
   /* mg was the first ext magic in the chain that had uvar */
 
   for (mg = moremagic; mg; mg = mg->mg_moremagic) {
-   if (mg->mg_type == PERL_MAGIC_ext && mg->mg_private == SIG_WIZ) {
-    const vmg_wizard *z = vmg_wizard_from_sv(mg->mg_ptr);
-    if (z->uvar) {
-     ++uvars;
-     break;
-    }
+   const vmg_wizard *z = vmg_wizard_from_mg(mg);
+
+   if (z && z->uvar) {
+    ++uvars;
+    break;
    }
   }
 
@@ -1072,17 +1070,19 @@ STATIC int vmg_cb_call(pTHX_ SV *cb, unsigned int flags, SV *sv, ...) {
         vmg_cb_call(aTHX_ (I), VMG_CB_FLAGS((OI), 3), (S), (A1), (A2), (A3))
 
 STATIC int vmg_svt_get(pTHX_ SV *sv, MAGIC *mg) {
- const vmg_wizard *w = vmg_wizard_from_sv(mg->mg_ptr);
+ const vmg_wizard *w = vmg_wizard_from_mg_nocheck(mg);
+
  return vmg_cb_call1(w->cb_get, w->opinfo, sv, mg->mg_obj);
 }
 
 STATIC int vmg_svt_set(pTHX_ SV *sv, MAGIC *mg) {
- const vmg_wizard *w = vmg_wizard_from_sv(mg->mg_ptr);
+ const vmg_wizard *w = vmg_wizard_from_mg_nocheck(mg);
+
  return vmg_cb_call1(w->cb_set, w->opinfo, sv, mg->mg_obj);
 }
 
 STATIC U32 vmg_svt_len(pTHX_ SV *sv, MAGIC *mg) {
- const vmg_wizard *w = vmg_wizard_from_sv(mg->mg_ptr);
+ const vmg_wizard *w = vmg_wizard_from_mg_nocheck(mg);
  unsigned int opinfo = w->opinfo;
  U32 len, ret;
  SV *svr;
@@ -1136,7 +1136,8 @@ STATIC U32 vmg_svt_len(pTHX_ SV *sv, MAGIC *mg) {
 }
 
 STATIC int vmg_svt_clear(pTHX_ SV *sv, MAGIC *mg) {
- const vmg_wizard *w = vmg_wizard_from_sv(mg->mg_ptr);
+ const vmg_wizard *w = vmg_wizard_from_mg_nocheck(mg);
+
  return vmg_cb_call1(w->cb_clear, w->opinfo, sv, mg->mg_obj);
 }
 
@@ -1152,7 +1153,7 @@ STATIC int vmg_svt_free(pTHX_ SV *sv, MAGIC *mg) {
  if (PL_dirty)
   return 0;
 
- w = vmg_wizard_from_sv(mg->mg_ptr);
+ w = vmg_wizard_from_mg_nocheck(mg);
 
  /* So that it survives the temp cleanup below */
  SvREFCNT_inc_simple_void(sv);
@@ -1202,7 +1203,7 @@ STATIC int vmg_svt_copy(pTHX_ SV *sv, MAGIC *mg, SV *nsv, const char *key,
   int keylen
 # endif
  ) {
- const vmg_wizard *w = vmg_wizard_from_sv(mg->mg_ptr);
+ const vmg_wizard *w = vmg_wizard_from_mg_nocheck(mg);
  SV *keysv;
  int ret;
 
@@ -1229,7 +1230,8 @@ STATIC int vmg_svt_dup(pTHX_ MAGIC *mg, CLONE_PARAMS *param) {
 
 #if MGf_LOCAL
 STATIC int vmg_svt_local(pTHX_ SV *nsv, MAGIC *mg) {
- const vmg_wizard *w = vmg_wizard_from_sv(mg->mg_ptr);
+ const vmg_wizard *w = vmg_wizard_from_mg_nocheck(mg);
+
  return vmg_cb_call1(w->cb_local, w->opinfo, nsv, mg->mg_obj);
 }
 #endif /* MGf_LOCAL */
@@ -1268,8 +1270,8 @@ STATIC I32 vmg_svt_val(pTHX_ IV action, SV *sv) {
    default:
     continue;
   }
-  if (mg->mg_private != SIG_WIZ) continue;
-  w = vmg_wizard_from_sv(mg->mg_ptr);
+  w = vmg_wizard_from_mg(mg);
+  if (!w) continue;
   switch (w->uvar) {
    case 0:
     continue;
@@ -1459,14 +1461,22 @@ OUTPUT:
 SV *cast(SV *sv, SV *wiz, ...)
 PROTOTYPE: \[$@%&*]$@
 PREINIT:
+ const vmg_wizard *w = NULL;
  SV **args = NULL;
+ UV ret;
  I32 i = 0;
 CODE:
  if (items > 2) {
   i = items - 2;
   args = &ST(2);
  }
- RETVAL = newSVuv(vmg_cast(SvRV(sv), vmg_wizard_sv_validate(wiz), args, i));
+ if (SvROK(wiz)) {
+  wiz = SvRV_const(wiz);
+  w   = vmg_wizard_from_sv(wiz);
+ }
+ if (!w)
+  croak(vmg_invalid_wiz);
+ RETVAL = newSVuv(vmg_cast(SvRV(sv), w, wiz, args, i));
 OUTPUT:
  RETVAL
 
@@ -1474,9 +1484,14 @@ void
 getdata(SV *sv, SV *wiz)
 PROTOTYPE: \[$@%&*]$
 PREINIT:
+ const vmg_wizard *w = NULL;
  SV *data;
 PPCODE:
- data = vmg_data_get(SvRV(sv), vmg_wizard_sv_validate(wiz));
+ if (SvROK(wiz))
+  w = vmg_wizard_from_sv(SvRV_const(wiz));
+ if (!w)
+  croak(vmg_invalid_wiz);
+ data = vmg_data_get(SvRV(sv), w);
  if (!data)
   XSRETURN_EMPTY;
  ST(0) = data;
@@ -1484,7 +1499,13 @@ PPCODE:
 
 SV *dispell(SV *sv, SV *wiz)
 PROTOTYPE: \[$@%&*]$
+PREINIT:
+ const vmg_wizard *w = NULL;
 CODE:
- RETVAL = newSVuv(vmg_dispell(SvRV(sv), vmg_wizard_sv_validate(wiz)));
+ if (SvROK(wiz))
+  w = vmg_wizard_from_sv(SvRV_const(wiz));
+ if (!w)
+  croak(vmg_invalid_wiz);
+ RETVAL = newSVuv(vmg_dispell(SvRV(sv), w));
 OUTPUT:
  RETVAL