linux-kernel - Re: [oss-security] [patch] proc.5: tell how to parse /proc/*/stat correctly

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Message-ID: <s5r028oo-n662-9qqq-9130-208poq85418p@vanv.qr>
Date:   Fri, 23 Dec 2022 01:21:42 +0100 (CET)
From:   Jan Engelhardt <jengelh@...i.de>
To:     oss-security@...ts.openwall.com
cc:     Alejandro Colomar <alx.manpages@...il.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        linux-kernel@...r.kernel.org, linux-man@...r.kernel.org
Subject: Re: [oss-security] [patch] proc.5: tell how to parse /proc/*/stat
 correctly


On Thursday 2022-12-22 23:03, Dominique Martinet wrote:
>> +
>> +Note that \fIcomm\fP can contain space and closing parenthesis characters. 
>> +Parsing /proc/${pid}/stat with split() or equivalent, or scanf(3) isn't
>> +reliable. The correct way is to locate closing parenthesis with strrchr(')')
>> +from the end of the buffer and parse integers from there.
>
>That's still not enough unless new lines are escaped, which they aren't:

strrchr does not concern itself with "lines".
If your input buffer contains the complete content of /proc/X/stat (and not
just a "line" thereof), the strrchr approach appears quite workable.