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panic: restore variable arguments to nmi_panic()

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nmi_panic() used to accept variable arguments until commit ebc41f20d7
("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.  panic_try_force_cpu() needs to print the
message but it is used also by panic() which accepts variable argument
list.  The string could be formatted only when a CPU gets assigned to
process the redirection.  Otherwise, there might be a race when writing
to the `panic_force_buf`.

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).

[pmladek@suse.com: changelog fix]
	Link: https://lore.kernel.org/arJxFybmtD7OBIcL@pathway.suse.cz
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>
Reviewed-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>
This commit is contained in:
Bradley Morgan 2026-09-16 18:29:55 +00:00 committed by Andrew Morton
parent 245001a347
commit ed9e4c1ff1
3 changed files with 11 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/watchdog/hpwdt.c
View File

@ -199,7 +199,7 @@ static int hpwdt_pretimeout(unsigned int ulReason, struct pt_regs *regs)
}
hex_byte_pack(panic_msg, nmistat);
nmi_panic(regs, panic_msg);
nmi_panic(regs, "%s", panic_msg);
return NMI_HANDLED;
}

3
include/linux/panic.h
View File

@ -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);

10
kernel/panic.c
View File

@ -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);