Make sure you use one of these versions if you're running 32-bit Redis. The problem is fixed in version 6.2, and the fix is back ported to 6.0.11 and 5.0.11. This problem only affects 32-bit Redis (on a 32-bit system, or as a 32-bit executable running on a 64-bit system).
#32 bit system timeout integer overflow code
We believe this could in certain conditions be exploited for remote code execution.īy default, authenticated Redis users have access to all configuration parameters and can therefore use the “CONFIG SET proto-max-bulk-len” to change the safe default, making the system vulnerable. If the limit is significantly increased, receiving a large request from a client may trigger several integer overflow scenarios, which would result with buffer overflow and heap corruption. By default, it is 512MB which is a safe value for all platforms. Redis 4.0 or newer uses a configurable limit for the maximum supported bulk input size. If the language uses an integer size that is the same as the pointer size, then a well constructed program will not overflow doing indexing calculations because it would necessarily have to run out of memory before the indexing calculations would cause overflow.An integer overflow bug in 32-bit Redis version 4.0 or newer could be exploited to corrupt the heap and potentially result with remote code execution. Indexing calculations (array indexing and/or pointer arithmetic) Even though there is no reason that the computation of (32769*65535) & 65535u should care about the upper bits of the result, gcc will use signed overflow as justification for ignoring the loop.īeyond the many answers that justify lack of overflow checking based on performance, there are two different kinds of arithmetic to consider: By its reasoning, the computation of (32769*65535) & 65535u would cause an overflow and there is thus no need for the compiler to consider any cases where (q | 32768) would yield a value larger than 32768. GCC will generate code for test2 which unconditionally increments (*p) once and returns 32768 regardless of the value passed into q. In case I need the performance, which is sometimes the case, I disable overflow checking using unchecked Data corruption is likely, security issues a possibility. Almost all code would behave erratically in the presence of overflows. I do appreciate the fact that I know that no operations overflow in production. The cost of accessing the database to generate (non-toy) HTML overshadows the overflow checking costs. I actually benchmarked this and I was not able to determine the difference. I run all of my production apps with overflow checking enabled. This means that the performance hit found in the made-up example above is totally irrelevant for our application. Nagios monitoring shows that the average CPU load stayed at 17%.
#32 bit system timeout integer overflow windows
I recompiled our server application (a Windows service analyzing data received from several sensors, quite some number crunching involved) with the /p:CheckForOverflowUnderflow="false" parameter (normally, I switch the overflow check on) and deployed it on a device. There may be situation where that is important, but for most applications, that won't matter.
But with the 10,000,000,000 repetitions, the time taken by a check is still less than 1 nanosecond. the checking steps take almost twice as long as adding the numbers (in total 3 times the original time). On my machine, the checked version takes 11015ms, while the unchecked version takes 4125ms. Let's execute a short C# program to test this assumption: Stopwatch watch = Stopwatch.StartNew() Ĭonsole.WriteLine() The first answers to this question express the excessive costs of checking. So: what are the design decisions behind such a dangerous behavior? That's a behavior which looks very risky to me, and wasn't the crash of Ariane 5 caused by such an overflow? That means there are some common programming languages which ignore Arithmetic Overflow by default (in C#, there are hidden options for changing that). Ever tried to sum up all numbers from 1 to 2,000,000 in your favorite programming language? The result is easy to calculate manually: 2,000,001,000,000, which some 900 times larger than the maximum value of an unsigned 32bit integer.Ĭ# prints out -1453759936 - a negative value! And I guess Java does the same.
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