From 00bff392c81e4fb1901e5160fdd5afdb2546a6ab Mon Sep 17 00:00:00 2001 From: Xiaotian Feng Date: Thu, 3 Mar 2011 18:08:24 +0800 Subject: [PATCH] tty_audit: fix tty_audit_add_data live lock on audit disabled The current tty_audit_add_data code: do { size_t run; run = N_TTY_BUF_SIZE - buf->valid; if (run > size) run = size; memcpy(buf->data + buf->valid, data, run); buf->valid += run; data += run; size -= run; if (buf->valid == N_TTY_BUF_SIZE) tty_audit_buf_push_current(buf); } while (size != 0); If the current buffer is full, kernel will then call tty_audit_buf_push_current to empty the buffer. But if we disabled audit at the same time, tty_audit_buf_push() returns immediately if audit_enabled is zero. Without emptying the buffer. With obvious effect on tty_audit_add_data() that ends up spinning in that loop, copying 0 bytes at each iteration and attempting to push each time without any effect. Holding the lock all along. Suggested-by: Alexander Viro Signed-off-by: Xiaotian Feng Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_audit.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/tty/tty_audit.c b/drivers/tty/tty_audit.c index f64582b0f623..7c5866920622 100644 --- a/drivers/tty/tty_audit.c +++ b/drivers/tty/tty_audit.c @@ -95,8 +95,10 @@ static void tty_audit_buf_push(struct task_struct *tsk, uid_t loginuid, { if (buf->valid == 0) return; - if (audit_enabled == 0) + if (audit_enabled == 0) { + buf->valid = 0; return; + } tty_audit_log("tty", tsk, loginuid, sessionid, buf->major, buf->minor, buf->data, buf->valid); buf->valid = 0; -- 2.39.5