This was originally meant to be a side project that we'd work on every once in a while, but with all of the extra free time with the pandemic we each ended up putting a few hundred hours into it.
There were a total of 55 vulnerabilities discovered with 11 critical severity, 29 high severity, 13 medium severity, and 2 low severity reports. These severities were assessed by us for summarization purposes and are dependent on a mix of CVSS and our understanding of the business related impact.
I figured that since we were to replace that matrix function anyway, I could try replacing it with XMMatrixInverse being a “modern” replacement for D3DXMatrixInverse. XMMatrixInverse also uses SSE2 instructions so it should be equally optimal to the D3DX function, but I was nearly sure it would break the same way.
Here’s Intel versus AMD relative error of RCPPS instruction: http://const.me/tmp/vrcpps-errors-chart.png AMD is Ryzen 5 3600, Intel is Core i3 6157U.
Over the complete range of floats, AMD is more precise on average, 0.000078 versus 0.000095 relative error. However, Intel has 0.000300 maximum relative error, AMD 0.000315.
Both are well within the spec. The documentation says “maximum relative error for this approximation is less than 1.5*2^-12”, in human language that would be 3.6621E-4.
Source code that compares them by creating 16GB binary files with the complete range of floats: https://gist.github.com/Const-me/a6d36f70a3a77de00c61cf4f6c17c7ac
至於為什麼會生出 NaN 的原因，沒找出來還是有點可惜，不過這個解法還行，就是「新版的 library 既然沒問題，就大家也不要太計較舊版的問題」的概念...
Whether PostgreSQL’s repeatable-read behavior is correct therefore depends on one’s interpretation of the standard. It is surprising that a database based on snapshot isolation would reject the strict interpretation chosen by the seminal paper on SI, but on reflection, the behavior is defensible.
The execution of concurrent SQL-transactions at isolation level SERIALIZABLE is guaranteed to be serializable. A serializable execution is defined to be an execution of the operations of concurrently executing SQL-transactions that produces the same effect as some serial execution of those same SQL-transactions. A serial execution is one in which each SQL-transaction executes to completion before the next SQL-transaction begins.
The random number generator is compliant with security and cryptographic standards such as NIST SP 800-90A, FIPS 140-2, and ANSI X9.82.
不過畢竟這個指令不是常常被使用，一般使用者的影響應該是還好：
As explained in the earlier article, mitigating CrossTalk involves locking the entire memory bus before updating the staging buffer and unlocking it after the contents have been cleared. This locking and serialization now involved for those instructions is very brutal on the performance, but thankfully most real-world workloads shouldn't be making too much use of these instructions.
We disclosed an initial PoC (Proof-Of-Concept) showing the leakage of staging buffer content in September 2018, followed by a PoC implementing cross-core RDRAND/RDSEED leakage in July 2019. Following our reports, Intel acknowledged the vulnerabilities, rewarded CrossTalk with the Intel Bug Bounty (Side Channel) Program, and attributed the disclosure to our team with no other independent finders. Intel also requested an embargo until May 2020 (later extended), due to the difficulty of implementing a fix for the cross-core vulnerabilities identified in this paper.
問題是當一個 certificate request 包含了 N 個 domain 時，本來的 CAA 檢查應該要對這 N 個檢查，但程式寫成只會抓一個，然後檢查了 N 次：
The bug: when a certificate request contained N domain names that needed CAA rechecking, Boulder would pick one domain name and check it N times. What this means in practice is that if a subscriber validated a domain name at time X, and the CAA records for that domain at time X allowed Let’s Encrypt issuance, that subscriber would be able to issue a certificate containing that domain name until X+30 days, even if someone later installed CAA records on that domain name that prohibit issuance by Let’s Encrypt.
We confirmed the bug at 2020-02-29 03:08 UTC, and halted issuance at 03:10. We deployed a fix at 05:22 UTC and then re-enabled issuance.
Our preliminary investigation suggests the bug was introduced on 2019-07-25. We will conduct a more detailed investigation and provide a postmortem when it is complete.
Q: How many certificates are affected?
A: 2.6%. That is 3,048,289 currently-valid certificates are affected, out of ~116 million overall active Let’s Encrypt certificates. Of the affected certificates, about 1 million are duplicates of other affected certificates, in the sense of covering the same set of domain names.
For the last few months Chrome has been seeing many "impossible" crashes on Intel Gemini Lake, family 6 model 122 stepping 1 CPUs. These crashes only happen with 64-bit Chrome and only happen in the prologue of two functions. The crashes come and go across different Chrome versions.
[–]edgan 1 point 2 months ago
It could br better, but it is far better than than Azure and GCP. Azure's old one was better than their new beta interface last I saw it. GCP has some interesting ideas, but the side bar centric design doesn't function well. It also tries to do too much, and is too JavaScript-y happy.
The new pi has been released and it has a USB Type-C connector for power however people are finding some chargers are not working with it (notably macbook chargers). Some have speculated that this is due to a manufacturer limitation on the power supplies however it is actually due to the incorrect detection circuitry on the Pi end of the USB connection.
這樣說有點偏頗，但是 Macbook 的充電器一向是 Type C 裡的指標，如果這顆充電器跟其他裝置配合上有問題，通常都是代表其他裝置的實作有問題... (噗)
這次發現的電阻問題看起來有點苦 (看起來需要改版子)，目前文章作者建議的 workaround 主要就是「不要用那麼好的設備」，比較簡單的包括了 Type C 的線不要那麼好 (像是找充手機用的線就好，不要找拿可以跑 5A 的線)，或是透過 Type A 轉 Type C 的線也應該可以避開這個問題，最差的情況應該是找其他的充電器：
Now onto some solutions. Assuming the issue you are having is caused by the problem discussed above, using a non e-marked cable (most USB-C phone charger cables are likely this type) rather than an e-marked cable (many laptop charger/thunderbolt cables and any 5A capable cable will be in this category) will allow for the pi to be powered. In addition using older chargers with A-C cables or micro B to C adaptors will also work if they provide enough power as these don’t require CC detection to provide power. Ultimately though the best solution in the long run will be for there to be a board revision for the pi 4 which adds the 2nd CC resistor and fixes the problem.
