From: Tom Lane <tgl@sss.pgh.pa.us>
To: Nathan Bossart <nathandbossart@gmail.com>
cc: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>,
        Abhijit Menon-Sen <ams@toroid.org>,
        Michael Paquier <michael@paquier.xyz>,
        Robert Haas <robertmhaas@gmail.com>, pgsql-hackers@postgresql.org
Subject: Re: introduce dynamic shared memory registry
In-reply-to: <20240119204636.GA1178173@nathanxps13>
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Comments: In-reply-to Nathan Bossart <nathandbossart@gmail.com>
	message dated "Fri, 19 Jan 2024 14:46:36 -0600"
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Date: Sun, 21 Jan 2024 11:21:46 -0500
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Nathan Bossart <nathandbossart@gmail.com> writes:
> Committed.  Thanks everyone for reviewing!

Coverity complained about this:

*** CID 1586660:  Null pointer dereferences  (NULL_RETURNS)
/srv/coverity/git/pgsql-git/postgresql/src/backend/storage/ipc/dsm_registr=
y.c: 185 in GetNamedDSMSegment()
179     	}
180     	else if (!dsm_find_mapping(entry->handle))
181     	{
182     		/* Attach to existing segment. */
183     		dsm_segment *seg =3D dsm_attach(entry->handle);
184     =

>>>     CID 1586660:  Null pointer dereferences  (NULL_RETURNS)
>>>     Dereferencing a pointer that might be "NULL" "seg" when calling "d=
sm_pin_mapping".
185     		dsm_pin_mapping(seg);
186     		ret =3D dsm_segment_address(seg);
187     	}
188     	else
189     	{
190     		/* Return address of an already-attached segment. */

I think it's right --- the comments for dsm_attach explicitly
point out that a NULL return is possible.  You need to handle
that scenario in some way other than SIGSEGV.

			regards, tom lane