Fix race condition in pg_ctl reading postmaster.pid.

If postmaster changed postmaster.pid while pg_ctl was reading it, pg_ctl
could overrun the buffer it allocated for the file. Fix by reading the
whole file to memory with one read() call.

initdb contains an identical copy of the readfile() function, but the files
that initdb reads are static, not modified concurrently. Nevertheless, add
a simple bounds-check there, if only to silence static analysis tools.

Per report from Dave Vitek. Backpatch to all supported branches.

1 files changed, 5 insertions, 4 deletions

diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index d5101fad2fc..f3e1d90dc41 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -368,6 +368,7 @@ readfile(const char *path)
 	int			maxlength = 1,
 				linelen = 0;
 	int			nlines = 0;
+	int			n;
 	char	  **result;
 	char	   *buffer;
 	int			c;
@@ -405,13 +406,13 @@ readfile(const char *path)
 
 	/* now reprocess the file and store the lines */
 	rewind(infile);
-	nlines = 0;
-	while (fgets(buffer, maxlength + 1, infile) != NULL)
-		result[nlines++] = xstrdup(buffer);
+	n = 0;
+	while (fgets(buffer, maxlength + 1, infile) != NULL && n < nlines)
+		result[n++] = xstrdup(buffer);
 
 	fclose(infile);
 	free(buffer);
-	result[nlines] = NULL;
+	result[n] = NULL;
 
 	return result;
 }