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Jakub Zawadzki changed bug 7676

What	Removed	Added
CC		turney_cal@emc.com
OS	FreeBSD	All

Comment # 12 on bug 7676 from Jakub Zawadzki

Hi,

(In reply to comment #11)
> I'm still seeing this problem with FreeBSD 9.0 running tshark 1.10.0.  Has
> this patch been incorporated into 1.10.0 or are we talking about a new issue?

Same one.

Finally found some time to debug it on FreeBSD:

#8 0x08067e45 in iostat_packet (arg=0x2b4b9f80, pinfo=0xbfbfe570,
edt=0xbfbfe568, dummy=0x0) at tap-iostat.c:127
127 it->next = (io_stat_item_t *)g_malloc(sizeof(io_stat_item_t));

(gdb) print relative_time
$1 = 18446744071567319020
(gdb) print /x relative_time
$2 = 0xffffffff80501fec
(gdb) print pinfo->fd->rel_ts.secs
$3 = 2152
(gdb) print /x (guint64)((pinfo->fd->rel_ts.secs*1000000))
$4 = 0xffffffff8044ea00
(gdb) print /x (guint64)(( ((guint)pinfo->fd->rel_ts.secs)*1000000))
$5 = 0x8044ea00

Some small test program:

#include <stdio.h>
#include <time.h>

int main() {
        unsigned long long rel_time;
        time_t secs;
        int nsecs;

        secs = 2152;
        nsecs = 100;

        rel_time = (unsigned long long)((secs*1000000) + ((nsecs+500)/1000));

        printf("%llx\n", rel_time);
        return 0;
}

64 bits:
$ clang a.c -m64; ./a.out 
8044ea00

32 bits:
$ clang a.c -m32; ./a.out 
ffffffff8044ea00

So it's problem with sign extension (multiplication
pinfo->fd->rel_ts.secs*1000000) is done for signed time_t, 
result of it is negative (in 32-bits) for secs >= 2148, after casting result to
unsigned long long, they got enlarged to *enormous* 64 bits value.


and we're doing loop

while (very_large_value >= very_small_value) {
  // allocate some memory 
  very_small_value += 1s;
}

it can quickly eat whole memory :)


Patch for it's quite simple:

-    relative_time = (guint64)((pinfo->fd->rel_ts.secs*1000000) +
((pinfo->fd->rel_ts.nsecs+500)/1000));
+    relative_time = (guint64)((pinfo->fd->rel_ts.secs*1000000U) +
((pinfo->fd->rel_ts.nsecs+500)/1000));

But whole code should be checked for 32 bits.


CCing Cal Turney.

Cheers,
Jakub.

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