+ panic-restore-variable-arguments-to-nmi_panic.patch added to mm-nonmm-unstable branch

+ panic-restore-variable-arguments-to-nmi_panic.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: panic: restore variable arguments to nmi_panic()
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     panic-restore-variable-arguments-to-nmi_panic.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/panic-restore-variable-arguments-to-nmi_panic.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: panic: restore variable arguments to nmi_panic()
Date: Wed, 16 Sep 2026 18:29:55 +0000

nmi_panic() used to accept variable arguments until commit ebc41f20d77f
("panic: change nmi_panic from macro to function") flattened it to a final
message string.  vpanic() did not exist back then, so the function had to
format through panic("%s", msg).

Bring the variable arguments back and format with vpanic() directly.  The
next patch makes nmi_panic() try the panic_force_cpu= redirect before
claiming panic_cpu, which needs the arguments twice: once to format the
message for the redirected CPU and once for vpanic() when no redirect
happens.  Passing a final string would lose that.

No current caller passes a string with format specifiers.  The closest one
is hpwdt_pretimeout(), which builds panic_msg with hex_byte_pack() and has
only two variants, both plain strings.  But the new __printf() annotation
on nmi_panic() would warn with -Wformat-security there because the buffer
is passed directly as the format argument, so switch it to nmi_panic(regs,
"%s", panic_msg).

Link: https://lore.kernel.org/20260916182957.7788-5-brads@mainlining.org
Signed-off-by: Bradley Morgan <brads@mainlining.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: Petr Mladek <pmladek@suse.com>
Cc: Guenetr Roeck <linux@roeck-us.net>
Cc: Sashiko <sashiko-bot@kernel.org>
Cc: Wang Jinchao <wangjinchao600@gmail.com>
Cc: Wim Van Sebroeck <wim@linux-watchdog.org>
Cc: <stable@vger.kernel.org>
---

 drivers/watchdog/hpwdt.c |    2 +-
 include/linux/panic.h    |    3 ++-
 kernel/panic.c           |   10 ++++++++--
 3 files changed, 11 insertions(+), 4 deletions(-)

--- a/drivers/watchdog/hpwdt.c~panic-restore-variable-arguments-to-nmi_panic
+++ a/drivers/watchdog/hpwdt.c
@@ -199,7 +199,7 @@ static int hpwdt_pretimeout(unsigned int
 	}
 
 	hex_byte_pack(panic_msg, nmistat);
-	nmi_panic(regs, panic_msg);
+	nmi_panic(regs, "%s", panic_msg);
 
 	return NMI_HANDLED;
 }
--- a/include/linux/panic.h~panic-restore-variable-arguments-to-nmi_panic
+++ a/include/linux/panic.h
@@ -13,7 +13,8 @@ __printf(1, 2)
 void panic(const char *fmt, ...) __noreturn __cold;
 __printf(1, 0)
 void vpanic(const char *fmt, va_list args) __noreturn __cold;
-void nmi_panic(struct pt_regs *regs, const char *msg);
+__printf(2, 3)
+void nmi_panic(struct pt_regs *regs, const char *fmt, ...);
 void check_panic_on_warn(const char *origin);
 extern void oops_enter(void);
 extern void oops_exit(void);
--- a/kernel/panic.c~panic-restore-variable-arguments-to-nmi_panic
+++ a/kernel/panic.c
@@ -518,13 +518,19 @@ EXPORT_SYMBOL(panic_on_other_cpu);
  * nmi_panic_self_stop() which can provide architecture dependent code such
  * as saving register state for crash dump.
  */
-void nmi_panic(struct pt_regs *regs, const char *msg)
+void nmi_panic(struct pt_regs *regs, const char *fmt, ...)
 {
+	va_list args;
+
+	va_start(args, fmt);
+
 	if (panic_try_start())
-		panic("%s", msg);
+		vpanic(fmt, args);
 
 	if (panic_on_other_cpu())
 		nmi_panic_self_stop(regs);
+
+	va_end(args);
 }
 EXPORT_SYMBOL(nmi_panic);
 
_

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