net: sockets: getaddrinfo() buffer overflow, etc. fixes

[pfalcon]

The existing implementation assumed DNS resolv callback will be
called just once, but that's not always the case (apparently,
for multi-homes hosts or something). So, apply array bounds
checking. In this case, port number wasn't set in each entry too,
so rework how it's done.

The issues discovered while resolving archive.ubuntu.com.

Signed-off-by: Paul Sokolovsky [email protected]

[codecov-io]

Codecov Report

Merging #6158 into master will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #6158      +/-   ##
==========================================
- Coverage   52.88%   52.87%   -0.01%     
==========================================
  Files         412      412              
  Lines       40274    40278       +4     
  Branches     7801     7802       +1     
==========================================
  Hits        21297    21297              
- Misses      15761    15765       +4     
  Partials     3216     3216

Impacted Files	Coverage Δ
subsys/net/lib/sockets/getaddrinfo.c	0% <0%> (ø)	⬆️

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[lpereira]

Good catch. Please also modify line 34 so that the pointer isn't even calculated if state->idx is out of bounds (it's undefined behavior); I can't seem to be able to comment in that line as it's not part of your patch.

[pfalcon]

the pointer isn't even calculated if state->idx is out of bounds (it's undefined behavior);

Are you sure that calculation is undefined behavior? Maybe accessing a pointer calculated in such a manner is undefined behavior?

[lpereira]

Yes, I'm sure. The only exception is calculating the pointer to one element past the end of an array (so it's possible to loop through an array using pointers rather than indices).

See the C11 text, 6.5.6.8:

If both the pointer operand and the result point to elements of the same array object, or
one past the last element of the array object, the evaluation shall not produce an overflow;
otherwise, the behavior is undefined.

[pfalcon]

Updated as suggested.

[lpereira]

Note for whoever is merging this: this should be backported to 1.10.

[nashif]

@pfalcon can you backport and submit to 1.10 branch?

[pfalcon]

can you backport and submit to 1.10 branch?

Submitted as #6169, thanks.