+ watchdog-perf-one-digit-too-short-in-the-raw-event-config-copy.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: watchdog/perf: one digit too short in the raw event config copy
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     watchdog-perf-one-digit-too-short-in-the-raw-event-config-copy.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/watchdog-perf-one-digit-too-short-in-the-raw-event-config-copy.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Bradley Morgan <brads@mainlining.org>
Subject: watchdog/perf: one digit too short in the raw event config copy
Date: Sat, 3 Oct 2026 11:02:00 +0000

Commit 6164be01f179 ("watchdog/perf: optimize bytes copied and remove
manual NUL-termination") swapped strscpy(buf, str, sizeof(buf)) plus a
manual buf[len] = 0 for strscpy(buf, str, len), and that count is one
short.  strscpy() keeps the last byte of the destination for the NUL, so
the config loses its final digit, nmi_watchdog=r300,panic for example ends
up with buf = "30" and arms the raw event with the wrong config.

The empty case falls over too, strscpy() with a zero count writes nothing
at all, so nmi_watchdog=r,1 leaves buf uninitialized and kstrtoull() reads
whatever stack garbage is sitting there.

The old code was safe on both by accident, it filled the whole buffer
first and buf[len] = 0 then stomped the comma position, so the worst you
got was a truncated parse failure.

Pass len + 1 so the copy includes the character the NUL replaces, and
reject len >= sizeof(buf) like it was before the optimization, which also
turns an empty config back into a clean parse failure.

Link: https://lore.kernel.org/20261003110200.3-brads@mainlining.org
Fixes: 6164be01f179 ("watchdog/perf: optimize bytes copied and remove manual NUL-termination")
Signed-off-by: Bradley Morgan <brads@mainlining.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Cc: Thorsten Blum <blum@kernel.org>
Cc: Thomas Gleixner <tglx@kernel.org>
---

 kernel/watchdog_perf.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/watchdog_perf.c~watchdog-perf-one-digit-too-short-in-the-raw-event-config-copy
+++ a/kernel/watchdog_perf.c
@@ -301,10 +301,10 @@ void __init hardlockup_config_perf_event
 	} else {
 		unsigned int len = comma - str;
 
-		if (len > sizeof(buf))
+		if (len >= sizeof(buf))
 			return;
 
-		strscpy(buf, str, len);
+		strscpy(buf, str, len + 1);
 		if (kstrtoull(buf, 16, &config))
 			return;
 	}
_

Patches currently in -mm which might be from brads@mainlining.org are

taskstats-copy-signal-stats-under-siglock-in-taskstats_exit.patch
mailmap-update-email-address-for-bradley-morgan.patch
taskstats-drop-the-unused-cpu_dont_care-enum-member.patch
panic-fix-redirect-cpu-race-in-panic_try_force_cpu.patch
panic-flatten-nmi_panic-control-flow.patch
panic-fix-va_list-reuse-in-panic_try_force_cpu.patch
panic-restore-variable-arguments-to-nmi_panic.patch
panic-allow-force_cpu-redirect-from-an-nmi.patch
panic-kill-the-buffer-unavailable-redirect-fallback.patch
watchdog-perf-one-digit-too-short-in-the-raw-event-config-copy.patch