On 2018/07/01 18:19, gregkh@xxxxxxxxxxxxxxxxxxx wrote: > > The patch below does not apply to the 4.9-stable tree. > If someone wants it applied there, or to any other stable or longterm > tree, then please email the backport, including the original git commit > id to <stable@xxxxxxxxxxxxxxx>. > OK. Filename and function name are different as of 4.9. Updated patch for 4.9-stable is attached below. >From 030b03ee5602e045398d8452afdcd136f3f5272c Mon Sep 17 00:00:00 2001 From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Date: Sun, 1 Jul 2018 19:34:37 +0900 Subject: [PATCH] printk: fix possible reuse of va_list variable commit 988a35f8da1dec5a8cd2788054d1e717be61bf25 upstream. 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(). Link: http://lkml.kernel.org/r/201805112002.GIF21216.OFVHFOMLJtQFSO@xxxxxxxxxxxxxxxxxxx Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> Cc: dvyukov@xxxxxxxxxx Cc: syzkaller@xxxxxxxxxxxxxxxx Cc: fengguang.wu@xxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Fixes: 42a0bb3f71383b45 ("printk/nmi: generic solution for safe printk in NMI") Cc: 4.7+ <stable@xxxxxxxxxxxxxxx> # v4.7+ Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx> Signed-off-by: Petr Mladek <pmladek@xxxxxxxx> --- kernel/printk/nmi.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/printk/nmi.c b/kernel/printk/nmi.c index 16bab47..5fa65aa 100644 --- a/kernel/printk/nmi.c +++ b/kernel/printk/nmi.c @@ -63,6 +63,7 @@ static int vprintk_nmi(const char *fmt, va_list args) struct nmi_seq_buf *s = this_cpu_ptr(&nmi_print_seq); int add = 0; size_t len; + va_list ap; again: len = atomic_read(&s->len); @@ -79,7 +80,9 @@ static int vprintk_nmi(const char *fmt, va_list args) if (!len) smp_rmb(); - add = vsnprintf(s->buffer + len, sizeof(s->buffer) - len, fmt, args); + va_copy(ap, args); + add = vsnprintf(s->buffer + len, sizeof(s->buffer) - len, fmt, ap); + va_end(ap); /* * Do it once again if the buffer has been flushed in the meantime. -- 1.8.3.1
