treewide: Don't rely on terminator records in ip[46].dns arrays

In our arrays of DNS resolvers to pass to the guest we use a blank entry
to indicate the end of the list.  We rely on this when scanning the array,
not having separate bounds checking.  clang-tidy 21.1.7 has fancier
checking for array overruns in loops, but it's not able to reason that
there's always a terminating entry, so complains.

Indeed, it's correct to do so in this case.  Although we allow space in the
arrays for the terminator (size MAXNS + 1), add_dns[46]() check only for
    idx >= ARRAY_SIZE()
before adding an entry.  This allows it to consume the last slot with a
"real" entry, meaning the places where we scan really could overrun.

Fix the bug, and make it easier to reason about (for both clang-tidy and
people) by using ARRAY_SIZE() base bounds checking.  Treat the terminator
explicitly as an early exit case using 'break'.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
[sbrivio: Fix up comments to @dns in structs ip4_ctx and ip6_ctx]
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

0 files changed, 0 insertions, 0 deletions