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

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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>
This commit is contained in:
Denys Vlasenko 2012-04-28 14:26:18 +02:00
parent 54432560a8
commit e0bc222263
3 changed files with 29 additions and 12 deletions
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1
defs.h
View File

@ -580,6 +580,7 @@ extern void printcall(struct tcb *);
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);

23
io.c
View File

@ -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)
{

17
net.c
View File

@ -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 @@ printcmsghdr(struct tcb *tcp, unsigned long addr, unsigned long len)
}
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 @@ do_msghdr(struct tcb *tcp, struct msghdr *msg)
}
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 @@ printmsghdr(struct tcb *tcp, long addr)
tprintf("%#lx", addr);
return;
}
do_msghdr(tcp, &msg);
do_msghdr(tcp, &msg, data_size);
}
static void
@ -1454,7 +1455,7 @@ printmmsghdr(struct tcb *tcp, long addr, unsigned int idx)
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 @@ sys_sendmsg(struct tcb *tcp)
{
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 @@ sys_recvmsg(struct tcb *tcp)
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_???");