Fix recvmsg decode: do not show more data than actually returned

[strace] / io.c

diff --git a/io.c b/io.c
index 5e697eca9d512d4954c68159e5f84dc239531dcb..bf5baa2968ed9b97b321e5370903932a7e3e6108 100644 (file)
--- a/io.c
+++ b/io.c
@@ -30,6 +30,7 @@
 
 #include "defs.h"
 #include <fcntl.h>
+#include <limits.h>
 #if HAVE_SYS_UIO_H
 # include <sys/uio.h>
 #endif
@@ -63,8 +64,12 @@ sys_write(struct tcb *tcp)
 }
 
 #if HAVE_SYS_UIO_H
+/*
+ * data_size limits the cumulative size of printed data.
+ * Example: recvmsg returing a short read.
+ */
 void
-tprint_iov(struct tcb *tcp, unsigned long len, unsigned long addr, int decode_iov)
+tprint_iov_upto(struct tcb *tcp, unsigned long len, unsigned long addr, int decode_iov, unsigned long data_size)
 {
 #if SUPPORTED_PERSONALITIES > 1
        union {
@@ -117,9 +122,13 @@ tprint_iov(struct tcb *tcp, unsigned long len, unsigned long addr, int decode_io
                        break;
                }
                tprints("{");
-               if (decode_iov)
-                       printstr(tcp, (long) iov_iov_base, iov_iov_len);
-               else
+               if (decode_iov) {
+                       unsigned long len = iov_iov_len;
+                       if (len > data_size)
+                               len = data_size;
+                       data_size -= len;
+                       printstr(tcp, (long) iov_iov_base, len);
+               } else
                        tprintf("%#lx", (long) iov_iov_base);
                tprintf(", %lu}", (unsigned long)iov_iov_len);
        }
@@ -131,6 +140,12 @@ tprint_iov(struct tcb *tcp, unsigned long len, unsigned long addr, int decode_io
 #undef iov_iov_len
 }
 
+void
+tprint_iov(struct tcb *tcp, unsigned long len, unsigned long addr, int decode_iov)
+{
+       tprint_iov_upto(tcp, len, addr, decode_iov, ULONG_MAX);
+}
+
 int
 sys_readv(struct tcb *tcp)
 {