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NTP sync failure if offset with BIOS date is greater than a signed long #450

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yhemery opened this issue Aug 30, 2021 · 3 comments · May be fixed by #455
Open

NTP sync failure if offset with BIOS date is greater than a signed long #450

yhemery opened this issue Aug 30, 2021 · 3 comments · May be fixed by #455

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@yhemery
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yhemery commented Aug 30, 2021

Hi,

On some servers with a BIOS date configured in 1921, the "ntp" iPXE command will succeed but the resulting system date is false. It looks this is due to an integer overflow starting here :

https://github.com/ipxe/ipxe/blob/master/src/net/udp/ntp.c#L116

When trying to boot an iPXE compiled with "DEBUG=ntp:1" on a server with a BIOS date in 1921, we get :

NTP 0xa068e6a8 sending request
NTP 0xa068e6a8 delta -1139207296 seconds

So, we end up with a negative offset instead of the expected value of 3153600000 seconds (100 years).

Feel free to ask if you need more details.

Yannick.
@NiKiZe
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NiKiZe commented Aug 30, 2021

Just have to ask, on what hw is this, and how did the clock end up in that state?

@yhemery
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yhemery commented Aug 30, 2021

Just have to ask, on what hw is this, and how did the clock end up in that state?

That's a Supermicro X11DPi-NT, they end up in 1921 if the CMOS battery is depleted or removed.

@yhemery
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yhemery commented Sep 3, 2021

PR #455 created, validated on an impacted system with a BIOS date set to 1921.

@yhemery yhemery linked a pull request Sep 3, 2021 that will close this issue
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[ntp] Offset with system date might be greater than a signed long yhemery/ipxe
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@NiKiZe @yhemery