+ watchdog-perf-reject-empty-config-before-the-raw-event-parse.patch added to mm-nonmm-unstable branch

+ watchdog-perf-reject-empty-config-before-the-raw-event-parse.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: watchdog/perf: reject empty config before the raw event parse
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     watchdog-perf-reject-empty-config-before-the-raw-event-parse.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/watchdog-perf-reject-empty-config-before-the-raw-event-parse.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: reject empty config before the raw event parse
Date: Fri, 2 Oct 2026 17:39:13 +0000

Commit 6164be01f179 ("watchdog/perf: optimize bytes copied and remove
manual NUL-termination") replaced strscpy(buf, str, sizeof(buf)) plus a
manual buf[len] = 0 with strscpy(buf, str, len).  strscpy() writes nothing
at all when the count is zero, so on a comma directly after the "r"
prefix, nmi_watchdog=r,1 for example, len is 0, buf stays uninitialized,
and kstrtoull() parses whatever stack garbage is there.

The old code was safe here by accident, strscpy() filled the whole buffer
before buf[len] = 0 overwrote the comma position, so a zero length just
produced an empty string and a clean parse failure.

Treat an empty config the same as an overlong one and return early.

Link: https://lore.kernel.org/20261002175000.1-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>
Cc: Thorsten Blum <blum@kernel.org>
Cc: Thomas Gleixner <tglx@kernel.org>
Cc: Douglas Anderson <dianders@chromium.org>
---

 kernel/watchdog_perf.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/watchdog_perf.c~watchdog-perf-reject-empty-config-before-the-raw-event-parse
+++ a/kernel/watchdog_perf.c
@@ -301,7 +301,7 @@ void __init hardlockup_config_perf_event
 	} else {
 		unsigned int len = comma - str;
 
-		if (len > sizeof(buf))
+		if (!len || len > sizeof(buf))
 			return;
 
 		strscpy(buf, str, len);
_

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-reject-empty-config-before-the-raw-event-parse.patch