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([41.238.114.180]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-439fe1a78cesm28064825f8f.11.2026.03.14.15.10.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 14 Mar 2026 15:11:00 -0700 (PDT) From: Osama Abdelkader To: Greg Kroah-Hartman , Jiri Slaby , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org Cc: Osama Abdelkader Subject: [PATCH] n_tty: add null check for tty->link in packet mode Date: Sat, 14 Mar 2026 23:10:44 +0100 Message-ID: <20260314221044.148442-1-osama.abdelkader@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add null check for tty->link before dereferencing in n_tty_read and n_tty_poll. When the pty master closes, tty->link can be NULL while the slave is still reading, causing a null pointer dereference. Signed-off-by: Osama Abdelkader --- drivers/tty/n_tty.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index e6a0f5b40d0a..dc04b87364f6 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -2232,7 +2232,7 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, u8 *kbuf, add_wait_queue(&tty->read_wait, &wait); while (nr) { /* First test for status change. */ - if (packet && tty->link->ctrl.pktstatus) { + if (packet && tty->link && tty->link->ctrl.pktstatus) { u8 cs; if (kb != kbuf) break; @@ -2444,7 +2444,7 @@ static __poll_t n_tty_poll(struct tty_struct *tty, struct file *file, if (input_available_p(tty, 1)) mask |= EPOLLIN | EPOLLRDNORM; } - if (tty->ctrl.packet && tty->link->ctrl.pktstatus) + if (tty->ctrl.packet && tty->link && tty->link->ctrl.pktstatus) mask |= EPOLLPRI | EPOLLIN | EPOLLRDNORM; if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) mask |= EPOLLHUP; -- 2.43.0