Re: [PATCH] FIx explicit null dereference pointer (nbtree.c) - Mailing list pgsql-hackers

On Wed, Apr 22, 2020 at 3:55 PM Ranier Vilela <ranier.vf@gmail.com> wrote:
> per Coverity.

Some Postgres hackers have access to a dedicated coverity
installation, and this issue has probably already been dismissed.

> 1. assign_zero: Assigning: opaque = NULL.
> 2. Condition buf < 0, taking true branch.
> 3. Condition !(((PageHeader)page)->pd_upper == 0), taking false branch.
> 4. Condition blkno != orig_blkno, taking true branch.
> 5. Condition _bt_page_recyclable(page), taking false branch.
> CID 1314742 (#2 of 2): Explicit null dereferenced (FORWARD_NULL)
> 6. var_deref_op: Dereferencing null pointer opaque.

This is a false positive. btvacuumpage() is supposed to be a recursive
function, but in practice the only caller always uses the same block
number for both blkno and orig_blkno -- the tail recursion is actually
implemented using goto/a loop.