git: d76303c9d326 - stable/12 - tty: Avoid a kernel memory discloure via kern.ttys

The branch stable/12 has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=d76303c9d326f1543fbe64f98b8a875228020910

commit d76303c9d326f1543fbe64f98b8a875228020910
Author:     Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2023-12-11 14:19:09 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2023-12-14 14:29:42 +0000

    tty: Avoid a kernel memory discloure via kern.ttys
    
    Four pad bytes at the end of each xtty structure were not being cleared
    before being copied out.  Fix this by clearing the whole structure
    before populating fields.
    
    MFC after:      3 days
    Reported by:    KMSAN
    
    (cherry picked from commit 3c0fb026b2fc998fa9bea8aed76e96c58671aee3)
---
 sys/kern/tty.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/sys/kern/tty.c b/sys/kern/tty.c
index f80ffd4921e6..c63a03183f1b 100644
--- a/sys/kern/tty.c
+++ b/sys/kern/tty.c
@@ -1279,6 +1279,7 @@ tty_to_xtty(struct tty *tp, struct xtty *xt)
 
 	tty_assert_locked(tp);
 
+	memset(xt, 0, sizeof(*xt));
 	xt->xt_size = sizeof(struct xtty);
 	xt->xt_insize = ttyinq_getsize(&tp->t_inq);
 	xt->xt_incc = ttyinq_bytescanonicalized(&tp->t_inq);