Merge branch 'issue09-esci2-img-buffer-size-check' into '279-confidential-issue'

epsonds: Prevent possible buffer overflow when reading image data

See merge request paddy-hack/backends!8

backend/epsonds-cmd.c

@@ -880,6 +880,11 @@ esci2_img(struct epsonds_scanner *s, SANE_Int *length)
 		return parse_status;
 	}
 
+	/* more data than was accounted for in s->buf */
+	if (more > s->bsz) {
+		return SANE_STATUS_IO_ERROR;
+	}
+
 	/* ALWAYS read image data */
 	if (s->hw->connection == SANE_EPSONDS_NET) {
 		epsonds_net_request_read(s, more);

backend/epsonds.c

@@ -1230,16 +1230,18 @@ sane_start(SANE_Handle handle)
 	if (s->line_buffer == NULL)
 		return SANE_STATUS_NO_MEM;
 
-	/* ring buffer for front page, twice bsz */
+	/* transfer buffer size, bsz */
 	/* XXX read value from scanner */
-	status = eds_ring_init(&s->front, (65536 * 4) * 2);
+	s->bsz = (65536 * 4);
+
+	/* ring buffer for front page */
+	status = eds_ring_init(&s->front, s->bsz * 2);
 	if (status != SANE_STATUS_GOOD) {
 		return status;
 	}
 
-	/* transfer buffer, bsz */
+	/* transfer buffer */
-	/* XXX read value from scanner */
+	s->buf = realloc(s->buf, s->bsz);
-	s->buf = realloc(s->buf, 65536 * 4);
 	if (s->buf == NULL)
 		return SANE_STATUS_NO_MEM;
 

backend/epsonds.h

@@ -160,6 +160,7 @@ struct epsonds_scanner
 	Option_Value val[NUM_OPTIONS];
 	SANE_Parameters params;
 
+	size_t bsz;		/* transfer buffer size */
 	SANE_Byte *buf, *line_buffer;
 	ring_buffer *current, front, back;