>From 766cf72b5fdc00d1cf5a8ca2c6b23ebb75e2b4d4 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> Date: Fri, 11 May 2018 19:54:19 +0900 Subject: [PATCH] printk: fix possible reuse of va_list variable
I noticed that there is a possibility that printk_safe_log_store() causes kernel oops because "args" parameter is passed to vsnprintf() again when atomic_cmpxchg() detected that we raced. Fix this by using va_copy(). Signed-off-by: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> Fixes: 42a0bb3f71383b45 ("printk/nmi: generic solution for safe printk in NMI") Cc: Sergey Senozhatsky <sergey.senozhat...@gmail.com> Cc: Petr Mladek <pmla...@suse.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Steven Rostedt <rost...@goodmis.org> --- kernel/printk/printk_safe.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c index 3e3c200..449d67e 100644 --- a/kernel/printk/printk_safe.c +++ b/kernel/printk/printk_safe.c @@ -82,6 +82,7 @@ static __printf(2, 0) int printk_safe_log_store(struct printk_safe_seq_buf *s, { int add; size_t len; + va_list ap; again: len = atomic_read(&s->len); @@ -100,7 +101,9 @@ static __printf(2, 0) int printk_safe_log_store(struct printk_safe_seq_buf *s, if (!len) smp_rmb(); - add = vscnprintf(s->buffer + len, sizeof(s->buffer) - len, fmt, args); + va_copy(ap, args); + add = vscnprintf(s->buffer + len, sizeof(s->buffer) - len, fmt, ap); + va_end(ap); if (!add) return 0; -- 1.8.3.1