Hello Denys,
After reading the posts of the mailing list for some days, I decided to
post again my message, sending it also directly to you.
I posted the attached patch by the ptxdist mailing list, and they
suggested to post it upstream.
I'm working with an old embedded system that is still using a 32 bit
time_t.
Upgrading busybox to 1.37.0 I encountered an unexpected crash in
the ntpd service. Specifically, when the one system acts as an ntpd
server, the crash occurs on the client side.
After investigating the issue, I believe I have identified a bug:
In the function that converts a double to the NTP time format, I found the
following code:
double d;
uint32_t intl;
intl = (uint32_t)(time_t)d;
where d is a double whose the integer part of d represents the number of
seconds since 1900-01-01T00:00:00.0
The number of seconds since 1900-01-01T00:00:00.0 is a number that exceed
the maximum capacity of my time_t, that is a 32bit signed integer.
Casting d to time_t in the server truncates the value to 0x7fffffff,
leading to a crash in the client.
The solution is to avoid the cast to time_t when sizeof(time_t) == 4,
basically checking if(sizeof(time_t) == 4), and in this case making the
assignment as it was before applying commit
85acf71d2579ebe4eec05c6f31901adffa700adc - ntpd: make NTP client and server
Y2036/2038-ready).
I have attached patch proposal for this issue.
Since the result of the condition
if(sizeof(time_t) == 4)
is known at compile time, any modern decent compiler should optimize it
out, so there is no impact on performance or size.
Best regards
Ruggero
Best regards,
Ruggero
Index: busybox-1.37.0/networking/ntpd.c
===================================================================
--- busybox-1.37.0.orig/networking/ntpd.c
+++ busybox-1.37.0/networking/ntpd.c
@@ -583,8 +583,13 @@ d_to_lfp(l_fixedpt_t *lfp, double d)
{
uint32_t intl;
uint32_t frac;
- intl = (uint32_t)(time_t)d;
- frac = (uint32_t)((d - (time_t)d) * 0xffffffff);
+ if(sizeof(time_t) == 4){
+ intl = (uint32_t)d;
+ frac = (uint32_t)((d - intl) * 0xffffffff);
+ }else{
+ intl = (uint32_t)(time_t)d;
+ frac = (uint32_t)((d - (time_t)d) * 0xffffffff);
+ }
lfp->int_partl = htonl(intl);
lfp->fractionl = htonl(frac);
}
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