bpo-40880: Fix invalid read in newline_in_string in pegen.c (#20666)

pablogsal · lysnikolaou · web-flow · commit 2e6593db0086 · 2020-06-06T00:52:27.000+01:00
* bpo-40880: Fix invalid read in newline_in_string in pegen.c * Update Parser/pegen/pegen.c Co-authored-by: Lysandros Nikolaou <lisandrosnik@gmail.com> * Add NEWS entry Co-authored-by: Lysandros Nikolaou <lisandrosnik@gmail.com>
diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-06-06-00-23-19.bpo-40880.fjdzSh.rst b/Misc/NEWS.d/next/Core and Builtins/2020-06-06-00-23-19.bpo-40880.fjdzSh.rst
@@ -0,0 +1,2 @@
+Fix invalid memory read in the new parser when checking newlines in string
+literals. Patch by Pablo Galindo.
diff --git a/Parser/pegen/pegen.c b/Parser/pegen/pegen.c
@@ -937,8 +937,8 @@ _PyPegen_number_token(Parser *p)
 static int // bool
 newline_in_string(Parser *p, const char *cur)
 {
-    for (char c = *cur; cur >= p->tok->buf; c = *--cur) {
-        if (c == '\'' || c == '"') {
+    for (const char *c = cur; c >= p->tok->buf; c--) {
+        if (*c == '\'' || *c == '"') {
             return 1;
         }
     }

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+Fix invalid memory read in the new parser when checking newlines in string`
	`2`	`+literals. Patch by Pablo Galindo.`
Original file line number	Diff line number	Diff line change
`@@ -937,8 +937,8 @@ _PyPegen_number_token(Parser *p)`
`937`	`937`	`static int // bool`
`938`	`938`	`newline_in_string(Parser p, const char cur)`
`939`	`939`	`{`
`940`		`- for (char c = cur; cur >= p->tok->buf; c = --cur) {`
`941`		`- if (c == '\'' \|\| c == '"') {`
	`940`	`+ for (const char *c = cur; c >= p->tok->buf; c--) {`
	`941`	`+ if (c == '\'' \|\| c == '"') {`
`942`	`942`	`return 1;`
`943`	`943`	`}`
`944`	`944`	`}`