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From: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
To: Daniel Gustafsson <daniel@yesql.se>
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: David Steele <david@pgmasters.net>
Cc: Cary Huang <cary.huang@highgo.ca>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: pg_rewind copies
Date: Mon, 4 Apr 2022 15:08:12 +0200
Message-ID: <97e6edb1-0f9a-685a-c860-0d886d8f94ba@enterprisedb.com> (raw)
In-Reply-To: <FBE3D7A0-4291-40F1-B4B7-637A440686C7@yesql.se>
References: <f67feb24-5833-88cb-1020-19a4a2b83ac7@iki.fi>
	<f67feb24-5833-88cb-1020-19a4a2b83ac7@iki.fi>
	<160807013024.1158.705820212542993455.pgcf@coridan.postgresql.org>
	<b2ebc855-61e3-818b-d6b8-cddf3e3d8816@iki.fi>
	<171fd136-d523-57fd-6f03-26eea9427136@pgmasters.net>
	<AF289C6A-109F-4B48-A27C-67264A4636B3@yesql.se>
	<FBE3D7A0-4291-40F1-B4B7-637A440686C7@yesql.se>

On 01.04.22 11:00, Daniel Gustafsson wrote:
> One small comment on the patch:
> 
> +   snprintf(srcpath, sizeof(srcpath), "%s/%s", datadir, path);
> 
> This should IMO check the returnvalue of snprintf to ensure it wasn't
> truncated.  While the risk is exceedingly small, a truncated filename might
> match another existing filename and the error not getting caught.  There is
> another instance just like this one in open_target_file() to which I think we
> should apply the same belts-and-suspenders treatment.  I've fixed this in the
> attached version which also have had a pg_indent run on top of a fresh rebase.

We use snprintf() like that countless times, and approximately none of 
them check for overflow.  So while you are right, this might not be the 
place to start a new policy.

If you don't like this approach, use psprintf() perhaps.





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