Issue #17016: Get rid of possible pointer wraparounds and integer overflows

in the re module.  Patch by Nickolai Zeldovich.

Misc/ACKS

@@ -1130,6 +1130,7 @@ Milan Zamazal
 Artur Zaprzala
 Mike Zarnstorff
 Siebren van der Zee
+Nickolai Zeldovich
 Uwe Zessin
 Cheng Zhang
 Tarek Ziadé

Misc/NEWS

@@ -25,6 +25,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #17016: Get rid of possible pointer wraparounds and integer overflows
+  in the re module.  Patch by Nickolai Zeldovich.
+
 - Issue #17536: Add to webbrowser's browser list: xdg-open, gvfs-open,
   www-browser, x-www-browser, chromium browsers, iceweasel, iceape.
 

Modules/_sre.c

@@ -686,7 +686,7 @@ do { \
     alloc_pos = state->data_stack_base; \
     TRACE(("allocating %s in %d (%d)\n", \
            SFY(type), alloc_pos, sizeof(type))); \
-    if (state->data_stack_size < alloc_pos+sizeof(type)) { \
+    if (sizeof(type) > state->data_stack_size - alloc_pos) { \
         int j = data_stack_grow(state, sizeof(type)); \
         if (j < 0) return j; \
         if (ctx_pos != -1) \
@@ -706,7 +706,7 @@ do { \
 do { \
     TRACE(("copy data in %p to %d (%d)\n", \
            data, state->data_stack_base, size)); \
-    if (state->data_stack_size < state->data_stack_base+size) { \
+    if (size > state->data_stack_size - state->data_stack_base) { \
         int j = data_stack_grow(state, size); \
         if (j < 0) return j; \
         if (ctx_pos != -1) \
@@ -1028,7 +1028,7 @@ entrance:
             TRACE(("|%p|%p|REPEAT_ONE %d %d\n", ctx->pattern, ctx->ptr,
                    ctx->pattern[1], ctx->pattern[2]));
 
-            if (ctx->ptr + ctx->pattern[1] > end)
+            if (ctx->pattern[1] > end - ctx->ptr)
                 RETURN_FAILURE; /* cannot match */
 
             state->ptr = ctx->ptr;
@@ -1111,7 +1111,7 @@ entrance:
             TRACE(("|%p|%p|MIN_REPEAT_ONE %d %d\n", ctx->pattern, ctx->ptr,
                    ctx->pattern[1], ctx->pattern[2]));
 
-            if (ctx->ptr + ctx->pattern[1] > end)
+            if (ctx->pattern[1] > end - ctx->ptr)
                 RETURN_FAILURE; /* cannot match */
 
             state->ptr = ctx->ptr;
@@ -2784,7 +2784,7 @@ _compile(PyObject* self_, PyObject* args)
         skip = *code;                                   \
         VTRACE(("%lu (skip to %p)\n",                   \
                (unsigned long)skip, code+skip));        \
-        if (code+skip-adj < code || code+skip-adj > end)\
+        if (skip-adj > end-code)                        \
             FAIL;                                       \
         code++;                                         \
     } while (0)
@@ -2817,7 +2817,7 @@ _validate_charset(SRE_CODE *code, SRE_CODE *end)
 
         case SRE_OP_CHARSET:
             offset = 32/sizeof(SRE_CODE); /* 32-byte bitmap */
-            if (code+offset < code || code+offset > end)
+            if (offset > end-code)
                 FAIL;
             code += offset;
             break;
@@ -2825,7 +2825,7 @@ _validate_charset(SRE_CODE *code, SRE_CODE *end)
         case SRE_OP_BIGCHARSET:
             GET_ARG; /* Number of blocks */
             offset = 256/sizeof(SRE_CODE); /* 256-byte table */
-            if (code+offset < code || code+offset > end)
+            if (offset > end-code)
                 FAIL;
             /* Make sure that each byte points to a valid block */
             for (i = 0; i < 256; i++) {
@@ -2834,7 +2834,7 @@ _validate_charset(SRE_CODE *code, SRE_CODE *end)
             }
             code += offset;
             offset = arg * 32/sizeof(SRE_CODE); /* 32-byte bitmap times arg */
-            if (code+offset < code || code+offset > end)
+            if (offset > end-code)
                 FAIL;
             code += offset;
             break;
@@ -2985,11 +2985,11 @@ _validate_inner(SRE_CODE *code, SRE_CODE *end, Py_ssize_t groups)
                     GET_ARG; prefix_len = arg;
                     GET_ARG; /* prefix skip */
                     /* Here comes the prefix string */
-                    if (code+prefix_len < code || code+prefix_len > newcode)
+                    if (prefix_len > newcode-code)
                         FAIL;
                     code += prefix_len;
                     /* And here comes the overlap table */
-                    if (code+prefix_len < code || code+prefix_len > newcode)
+                    if (prefix_len > newcode-code)
                         FAIL;
                     /* Each overlap value should be < prefix_len */
                     for (i = 0; i < prefix_len; i++) {
@@ -3118,7 +3118,7 @@ _validate_inner(SRE_CODE *code, SRE_CODE *end, Py_ssize_t groups)
                to allow arbitrary jumps anywhere in the code; so we just look
                for a JUMP opcode preceding our skip target.
             */
-            if (skip >= 3 && code+skip-3 >= code &&
+            if (skip >= 3 && skip-3 < end-code &&
                 code[skip-3] == SRE_OP_JUMP)
             {
                 VTRACE(("both then and else parts present\n"));