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 <aviro@redhat.com>
Signed-off-by: Xiaotian Feng <dfeng@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/tty/tty_audit.c b/drivers/tty/tty_audit.c
index f64582b..7c58669 100644
--- a/drivers/tty/tty_audit.c
+++ b/drivers/tty/tty_audit.c
@@ -95,8 +95,10 @@
{
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;