Fix recvmsg decode: do not show more data than actually returned
I noticed that "hostname -d" talks over netlink and gets 20 bytes
of response, but we show entire 1024 bytes of iov.
This changes fixes that.
* defs.h: New function tprint_iov_upto.
* io.c (tprint_iov_upto): Definition of this function.
(tprint_iov): Call tprint_iov_upto.
* net.c (do_msghdr): Add data_size parameter, pass it down to tprint_iov_upto.
(printmsghdr): Add data_size parameter, pass it down to do_msghdr.
(printmmsghdr): Call do_msghdr with data_size==ULONG_MAX.
(sys_sendmsg): Call printmsghdr with data_size==ULONG_MAX.
(sys_recvmsg): Call printmsghdr with data_size==tcp->u_rval.
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/defs.h b/defs.h
index 541e163..62f35b4 100644
--- a/defs.h
+++ b/defs.h
@@ -580,6 +580,7 @@
extern void print_sigset(struct tcb *, long, int);
extern void printsignal(int);
extern void tprint_iov(struct tcb *, unsigned long, unsigned long, int decode_iov);
+extern void tprint_iov_upto(struct tcb *, unsigned long, unsigned long, int decode_iov, unsigned long);
extern void tprint_open_modes(mode_t);
extern const char *sprint_open_modes(mode_t);
extern void print_loff_t(struct tcb *, long);
diff --git a/io.c b/io.c
index 5e697ec..bf5baa2 100644
--- 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 @@
}
#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 @@
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 @@
#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)
{
diff --git a/net.c b/net.c
index c7f0b97..fba521b 100644
--- a/net.c
+++ b/net.c
@@ -29,6 +29,7 @@
*/
#include "defs.h"
+#include <limits.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/un.h>
@@ -1405,14 +1406,14 @@
}
static void
-do_msghdr(struct tcb *tcp, struct msghdr *msg)
+do_msghdr(struct tcb *tcp, struct msghdr *msg, unsigned long data_size)
{
tprintf("{msg_name(%d)=", msg->msg_namelen);
printsock(tcp, (long)msg->msg_name, msg->msg_namelen);
tprintf(", msg_iov(%lu)=", (unsigned long)msg->msg_iovlen);
- tprint_iov(tcp, (unsigned long)msg->msg_iovlen,
- (unsigned long)msg->msg_iov, 1);
+ tprint_iov_upto(tcp, (unsigned long)msg->msg_iovlen,
+ (unsigned long)msg->msg_iov, 1, data_size);
#ifdef HAVE_STRUCT_MSGHDR_MSG_CONTROL
tprintf(", msg_controllen=%lu", (unsigned long)msg->msg_controllen);
@@ -1429,7 +1430,7 @@
}
static void
-printmsghdr(struct tcb *tcp, long addr)
+printmsghdr(struct tcb *tcp, long addr, unsigned long data_size)
{
struct msghdr msg;
@@ -1437,7 +1438,7 @@
tprintf("%#lx", addr);
return;
}
- do_msghdr(tcp, &msg);
+ do_msghdr(tcp, &msg, data_size);
}
static void
@@ -1454,7 +1455,7 @@
return;
}
tprints("{");
- do_msghdr(tcp, &mmsg.msg_hdr);
+ do_msghdr(tcp, &mmsg.msg_hdr, ULONG_MAX);
tprintf(", %u}", mmsg.msg_len);
}
@@ -1638,7 +1639,7 @@
{
if (entering(tcp)) {
tprintf("%ld, ", tcp->u_arg[0]);
- printmsghdr(tcp, tcp->u_arg[1]);
+ printmsghdr(tcp, tcp->u_arg[1], ULONG_MAX);
/* flags */
tprints(", ");
printflags(msg_flags, tcp->u_arg[2], "MSG_???");
@@ -1738,7 +1739,7 @@
if (syserror(tcp) || !verbose(tcp))
tprintf("%#lx", tcp->u_arg[1]);
else
- printmsghdr(tcp, tcp->u_arg[1]);
+ printmsghdr(tcp, tcp->u_arg[1], tcp->u_rval);
/* flags */
tprints(", ");
printflags(msg_flags, tcp->u_arg[2], "MSG_???");