lib/libc: Fix uninitialized value in __setenv()

[arichardson]

Summary

Reported indirectly via MK_UBSAN:
lib/libc/stdlib/getenv.c:169:20: runtime error: load of value 190, which is not a valid value for type 'bool'

MFC after: 3 days

[arichardson]

ping?

[arichardson]

ping?

[oshogbo]

If I understand correctly, the envVars with the putenv can't be reused.
So the putenv actually is set to 0 (as we are doing calloc'ing the memory needed for envVars), and we are 0 memory when we needed.
So besides the unhappy MK_UBSAN, there are no functional changes, as well as there is no security implication.
If I'm wrong at some of these statements, please correct me.

[arichardson]

Well ubsan is complaining that it loaded a value of 190 so that memory clearly wasn't zeroed.

[delphij]

I have some reservation with the proposed change. Basically the existing code is assuming that unused environment slots are zeroed (and they should be), so if I was you I'd probably amend the code around the two reallocarray's by zeroing out the newly added memory instead.

[oshogbo]

Oh. Right.
I didn't noticed that after realloc the memory is not cleaned.
Yes, I also would go with @delphij suggestion.

[arichardson]

Sounds good, happy to zero after realloc instead. Will update soon.

[arichardson]

Zero after realloc instead

[kib]

lib/libc/stdlib/getenv.c

283

environSize * sizeof(*intEnviron) is the common subexpression in both src and size. I suspect that extracting it into temp variable would improve readability (there and in second chunk)

[oshogbo]

Hello Alexander,

Do you plan to address @kib suggestion and commit it?

Thanks!