CVE-2023-52676

In the Linux kernel, the following vulnerability has been resolved:

bpf: Guard stack limits against 32bit overflow

This patch promotes the arithmetic around checking stack bounds to be

done in the 64-bit domain, instead of the current 32bit. The arithmetic

implies adding together a 64-bit register with a int offset. The

register was checked to be below 1<<29 when it was variable, but not

when it was fixed. The offset either comes from an instruction (in which

case it is 16 bit), from another register (in which case the caller

checked it to be below 1<<29 [1]), or from the size of an argument to a

kfunc (in which case it can be a u32 [2]). Between the register being

inconsistently checked to be below 1<<29, and the offset being up to an

u32, it appears that we were open to overflowing the `int`s which were

currently used for arithmetic.

[1] https://github.com/torvalds/linux/blob/815fb87b753055df2d9e50f6cd80eb10235fe3e9/kernel/bpf/verifier.c#L7494-L7498

[2] https://github.com/torvalds/linux/blob/815fb87b753055df2d9e50f6cd80eb10235fe3e9/kernel/bpf/verifier.c#L11904