linux-kernel - [PATCH] sysinfo: Saturate 16-bit procs rather than wrapping

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Message-ID: <e32ea9a03d0797ce2b8e7a82ed59c0dad9431f2b.1680407255.git.josh@joshtriplett.org>
Date:   Sun, 2 Apr 2023 12:57:29 +0900
From:   Josh Triplett <josh@...htriplett.org>
To:     linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Joey Gouly <joey.gouly@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alexey Gladkov <legion@...nel.org>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Mark Brown <broonie@...nel.org>
Subject: [PATCH] sysinfo: Saturate 16-bit procs rather than wrapping

struct sysinfo has a 16-bit field for the number of processes. Current
systems can easily exceed this. Rather than wrapping around, saturate
the value at U16_MAX. This is still incorrect, but more likely to
help the user know what's going on; a caller can then (for instance)
parse the full value out of /proc/loadavg.

Signed-off-by: Josh Triplett <josh@...htriplett.org>
---

Not sure what tree changes to kernel/sys.c should flow through. Andrew,
could you take this through your tree (assuming you agree with it), or
suggest what tree it should go through instead?

diff --git a/kernel/sys.c b/kernel/sys.c
index 495cd87d9bf4..ba05fca26927 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2699,7 +2699,7 @@ static int do_sysinfo(struct sysinfo *info)

 	get_avenrun(info->loads, 0, SI_LOAD_SHIFT - FSHIFT);

-	info->procs = nr_threads;
+	info->procs = min_t(typeof(nr_threads), nr_threads, U16_MAX);

 	si_meminfo(info);
 	si_swapinfo(info);
-- 
2.40.0