fix dirty NIF invalid memory read

Dirty NIF support used an Export structure to facilitate calls to dirty
NIFs and finalizers, but Export isn't large enough to hold all necessary
data. This was causing an invalid memory read in beam_emu.c past the end of
the Export object. Add a local extended Export struct to erl_nif.c that can
hold all the necessary data.

1 files changed, 26 insertions, 16 deletions

diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c
index 063dba056e..f503b222d0 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -1515,19 +1515,28 @@ int enif_consume_timeslice(ErlNifEnv* env, int percent)
 
 #ifdef ERTS_DIRTY_SCHEDULERS
 
+/* NIFs exports need one more item than the Export struct provides, the
+ * erl_module_nif*, so the DirtyNifExport below adds that. The Export
+ * member must be first in the struct.
+ */
+typedef struct {
+    Export exp;
+    struct erl_module_nif* m;
+} DirtyNifExport;
+
 static void
-alloc_proc_psd(Process* proc, Export **ep)
+alloc_proc_psd(Process* proc, DirtyNifExport **ep)
 {
     int i;
     if (!*ep) {
-	*ep = erts_alloc(ERTS_ALC_T_PSD, sizeof(Export));
-	sys_memset((void*) *ep, 0, sizeof(Export));
+	*ep = erts_alloc(ERTS_ALC_T_PSD, sizeof(DirtyNifExport));
+	sys_memset((void*) *ep, 0, sizeof(DirtyNifExport));
 	for (i=0; i<ERTS_NUM_CODE_IX; i++) {
-	    (*ep)->addressv[i] = &(*ep)->code[3];
+	    (*ep)->exp.addressv[i] = &(*ep)->exp.code[3];
 	}
-	(*ep)->code[3] = (BeamInstr) em_call_nif;
+	(*ep)->exp.code[3] = (BeamInstr) em_call_nif;
     }
-    (void) ERTS_PROC_SET_DIRTY_SCHED_TRAP_EXPORT(proc, ERTS_PROC_LOCK_MAIN, *ep);
+    (void) ERTS_PROC_SET_DIRTY_SCHED_TRAP_EXPORT(proc, ERTS_PROC_LOCK_MAIN, &(*ep)->exp);
 }
 
 static ERL_NIF_TERM
@@ -1560,7 +1569,7 @@ enif_schedule_dirty_nif(ErlNifEnv* env, int flags,
     erts_aint32_t state, n, a;
     Process* proc = env->proc;
     Eterm* reg = ERTS_PROC_GET_SCHDATA(proc)->x_reg_array;
-    Export* ep = NULL;
+    DirtyNifExport* ep = NULL;
     int i;
 
     int chkflgs = (flags & (ERL_NIF_DIRTY_JOB_IO_BOUND|ERL_NIF_DIRTY_JOB_CPU_BOUND));
@@ -1585,15 +1594,16 @@ enif_schedule_dirty_nif(ErlNifEnv* env, int flags,
 	if (a == state)
 	    break;
     }
-    if (!(ep = ERTS_PROC_GET_DIRTY_SCHED_TRAP_EXPORT(proc)))
+    if (!(ep = (DirtyNifExport*) ERTS_PROC_GET_DIRTY_SCHED_TRAP_EXPORT(proc)))
 	alloc_proc_psd(proc, &ep);
     ERTS_VBUMP_ALL_REDS(proc);
-    ep->code[2] = argc;
+    ep->exp.code[2] = argc;
     for (i = 0; i < argc; i++) {
 	reg[i] = (Eterm) argv[i];
     }
-    proc->i = (BeamInstr*) ep->addressv[0];
-    ep->code[4] = (BeamInstr) fp;
+    proc->i = (BeamInstr*) ep->exp.addressv[0];
+    ep->exp.code[4] = (BeamInstr) fp;
+    ep->m = env->mod_nif;
     proc->freason = TRAP;
 
     return THE_NON_VALUE;
@@ -1609,17 +1619,17 @@ enif_schedule_dirty_nif_finalizer(ErlNifEnv* env, ERL_NIF_TERM result,
 #ifdef USE_THREADS
     Process* proc = env->proc;
     Eterm* reg = ERTS_PROC_GET_SCHDATA(proc)->x_reg_array;
-    Export* ep;
+    DirtyNifExport* ep;
 
     erts_smp_atomic32_read_band_mb(&proc->state,
 				   ~(ERTS_PSFLG_DIRTY_CPU_PROC
 				     |ERTS_PSFLG_DIRTY_IO_PROC
 				     |ERTS_PSFLG_DIRTY_CPU_PROC_IN_Q
 				     |ERTS_PSFLG_DIRTY_IO_PROC_IN_Q));
-    if (!(ep = ERTS_PROC_GET_DIRTY_SCHED_TRAP_EXPORT(proc)))
+    if (!(ep = (DirtyNifExport*) ERTS_PROC_GET_DIRTY_SCHED_TRAP_EXPORT(proc)))
 	alloc_proc_psd(proc, &ep);
     ERTS_VBUMP_ALL_REDS(proc);
-    ep->code[2] = 2;
+    ep->exp.code[2] = 2;
     reg[0] = (Eterm) result;
 #if HAVE_INT64 && SIZEOF_LONG != 8
     ASSERT(sizeof(fp) <= sizeof(ErlNifUInt64));
@@ -1628,8 +1638,8 @@ enif_schedule_dirty_nif_finalizer(ErlNifEnv* env, ERL_NIF_TERM result,
     ASSERT(sizeof(fp) <= sizeof(unsigned long));
     reg[1] = (Eterm) enif_make_ulong(env, (unsigned long) fp);
 #endif
-    proc->i = (BeamInstr*) ep->addressv[0];
-    ep->code[4] = (BeamInstr) execute_dirty_nif_finalizer;
+    proc->i = (BeamInstr*) ep->exp.addressv[0];
+    ep->exp.code[4] = (BeamInstr) execute_dirty_nif_finalizer;
     proc->freason = TRAP;
 
     return THE_NON_VALUE;