4.17-stable review patch. If anyone has any objections, please let me know.
------------------
From: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp
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@I-love.SAKURA.... Cc: Peter Zijlstra peterz@infradead.org Cc: Steven Rostedt rostedt@goodmis.org Cc: dvyukov@google.com Cc: syzkaller@googlegroups.com Cc: fengguang.wu@intel.com Cc: linux-kernel@vger.kernel.org Signed-off-by: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp Fixes: 42a0bb3f71383b45 ("printk/nmi: generic solution for safe printk in NMI") Cc: 4.7+ stable@vger.kernel.org # v4.7+ Reviewed-by: Sergey Senozhatsky sergey.senozhatsky@gmail.com Signed-off-by: Petr Mladek pmladek@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/printk/printk_safe.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/kernel/printk/printk_safe.c +++ b/kernel/printk/printk_safe.c @@ -82,6 +82,7 @@ static __printf(2, 0) int printk_safe_lo { int add; size_t len; + va_list ap;
again: len = atomic_read(&s->len); @@ -100,7 +101,9 @@ again: 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;