Subject: [PATCH] contrib/xml2: guard against signed integer overflow in parse_params

From: Varik Matevosyan <[email-masked]>
Date: Mon, 4 May 2026 15:26:50 +0400

Hi,

Small robustness fix for contrib/xml2/parse_params. The doubling
of max_params relies on signed-integer overflow wrapping to a value
that AllocSizeIsValid then rejects, which is both UB and incidental
safety.

The overflow is unreachable in current builds (text input is bounded
by MaxAllocSize, which limits nparams below the doubling threshold),
but the fix is small and matches the explicit overflow-checking
idiom used elsewhere in the tree.

Patch attached against current master.

Regards,
Varik

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From: Tom Lane <[email-masked]>
Date: Mon, 04 May 2026 09:21:00 -0400

> that AllocSizeIsValid then rejects, which is both UB and incidental

There are many many places in our tree that handle that the same way.
The argument that it's UB is nonsense, because AllocSizeIsValid
rejects values >= 1G, so that it will fail on the iteration before
the integer counter can overflow.  (This is indeed exactly why that
limit is 1G and not 2G; see the comment for MaxAllocSize.)

I think this proposal makes parse_params less like other code,
not more so, so I don't think we need extra code here.

			regards, tom lane