Tony Finch 03e0083e3b Avoid using C99 variable length arrays ... From an attacker's point of view, a VLA declaration is essentially a primitive for performing arbitrary arithmetic on the stack pointer. If the attacker can control the size of a VLA they have a very powerful tool for causing memory corruption. To mitigate this kind of attack, and the more general class of stack clash vulnerabilities, C compilers insert extra code when allocating a VLA to probe the growing stack one page at a time. If these probes hit the stack guard page, the program will crash. From the point of view of a C programmer, there are a few things to consider about VLAs: * If it is important to handle allocation failures in a controlled manner, don't use VLAs. You can use VLAs if it is OK for unreasonable inputs to cause an uncontrolled crash. * If the VLA is known to be smaller than some known fixed size, use a fixed size array and a run-time check to ensure it is large enough. This will be more efficient than the compiler's stack probes that need to cope with arbitrary-size VLAs. * If the VLA might be large, allocate it on the heap. The heap allocator can allocate multiple pages in one shot, whereas the stack clash probes work one page at a time. Most of the existing uses of VLAs in BIND are in test code where they are benign, but there was one instance in `named`, in the GSS-TSIG verification code, which has now been removed. This commit adjusts the style guide and the C compiler flags to allow VLAs in test code but not elsewhere. (cherry picked from commit 599c1d2a6b)		2022-03-18 16:05:56 +00:00
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copyrights	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
dev.md	Drop references to Windows in doc/dev	2022-03-10 14:53:21 +00:00
HOW-ADB-WORKS.txt	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
rdata.md	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
results	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
style.md	Avoid using C99 variable length arrays	2022-03-18 16:05:56 +00:00
unexpected	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00