From 70158ed8bc74ce80a049c1beb71e85ae949778b2 Mon Sep 17 00:00:00 2001
From: Mattias Andrée <maandree@kth.se>
Date: Tue, 10 Jan 2017 20:07:02 +0100
Subject: Refuse infinite writes to regular files
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Signed-off-by: Mattias Andrée <maandree@kth.se>
---
 src/stream.c           | 32 ++++++++++++++------------------
 src/stream.h           | 34 +++++++++++++++++++++++++++++++---
 src/vu-repeat.c        |  3 +++
 src/vu-single-colour.c |  3 +++
 4 files changed, 51 insertions(+), 21 deletions(-)

diff --git a/src/stream.c b/src/stream.c
index e99d003..cb487ad 100644
--- a/src/stream.c
+++ b/src/stream.c
@@ -2,17 +2,12 @@
 #include "stream.h"
 #include "util.h"
 
+#include <sys/stat.h>
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 
-void
-einit_stream(struct stream *stream)
-{
-	eninit_stream(1, stream);
-}
-
 void
 eninit_stream(int status, struct stream *stream)
 {
@@ -103,12 +98,6 @@ set_pixel_size(struct stream *stream)
 	return 0;
 }
 
-void
-eset_pixel_size(struct stream *stream)
-{
-	enset_pixel_size(1, stream);
-}
-
 void
 enset_pixel_size(int status, struct stream *stream)
 {
@@ -126,12 +115,8 @@ fprint_stream_head(FILE *fp, struct stream *stream)
 }
 
 
-size_t eread_stream(struct stream *stream, size_t n)
-{
-	return enread_stream(1, stream, n);
-}
-
-size_t enread_stream(int status, struct stream *stream, size_t n)
+size_t
+enread_stream(int status, struct stream *stream, size_t n)
 {
 	ssize_t r = read(stream->fd, stream->buf + stream->ptr,
 			 sizeof(stream->buf) - stream->ptr < n ?
@@ -141,3 +126,14 @@ size_t enread_stream(int status, struct stream *stream, size_t n)
 	stream->ptr += (size_t)r;
 	return (size_t)r;
 }
+
+
+void
+eninf_check_fd(int status, int fd, const char *file)
+{
+	struct stat st;
+	if (fstat(fd, &st))
+		eprintf("fstat %s:", file);
+	if (S_ISREG(st.st_mode))
+		eprintf("%s is a regular file, refusing infinite write\n");
+}
diff --git a/src/stream.h b/src/stream.h
index ccba77f..26771fa 100644
--- a/src/stream.h
+++ b/src/stream.h
@@ -15,14 +15,42 @@ struct stream
 	const char *file;
 };
 
-void einit_stream(struct stream *stream);
+
 void eninit_stream(int status, struct stream *stream);
 
+static inline void
+einit_stream(struct stream *stream)
+{
+	eninit_stream(1, stream);
+}
+
+
 int set_pixel_size(struct stream *stream);
-void eset_pixel_size(struct stream *stream);
 void enset_pixel_size(int status, struct stream *stream);
 
+static inline void
+eset_pixel_size(struct stream *stream)
+{
+	enset_pixel_size(1, stream);
+}
+
+
 void fprint_stream_head(FILE *fp, struct stream *stream);
 
-size_t eread_stream(struct stream *stream, size_t n);
+
 size_t enread_stream(int status, struct stream *stream, size_t n);
+
+static inline size_t
+eread_stream(struct stream *stream, size_t n)
+{
+	return enread_stream(1, stream, n);
+}
+
+
+void eninf_check_fd(int status, int fd, const char *file);
+
+static inline void
+einf_check_fd(int fd, const char *file)
+{
+	eninf_check_fd(1, fd, file);
+}
diff --git a/src/vu-repeat.c b/src/vu-repeat.c
index 16f88cd..87eb3f9 100644
--- a/src/vu-repeat.c
+++ b/src/vu-repeat.c
@@ -38,6 +38,9 @@ main(int argc, char *argv[])
 		eprintf("the count must be an integer in [0, %zu]\n", SIZE_MAX);
 	}
 
+	if (inf)
+		einf_check_fd(STDOUT_FILENO, "<stdout>");
+
 	stream.file = argv[1];
 	stream.fd = open(stream.file, O_RDONLY);
 	if (stream.fd < 0)
diff --git a/src/vu-single-colour.c b/src/vu-single-colour.c
index 911dd11..6148205 100644
--- a/src/vu-single-colour.c
+++ b/src/vu-single-colour.c
@@ -69,6 +69,9 @@ main(int argc, char *argv[])
 	if (!(argc & 1) && tolf(argv[argc - 1], &alpha))
 		eprintf("the alpha value must be a floating-point value\n");
 
+	if (inf)
+		einf_check_fd(STDOUT_FILENO, "<stdout>");
+
 	strcpy(stream.pixfmt, "xyza");
 	fprint_stream_head(stdout, &stream);
 	fflush(stdout);
-- 
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