From: Nguyen Dinh Phi phind.uet@gmail.com
stable inclusion from stable-5.10.65 commit ae95c3a147d5a40465c39e538ed82ba9bb0ea4d0 bugzilla: 182361 https://gitee.com/openeuler/kernel/issues/I4EH3U
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit bb2853a6a421a052268eee00fd5d3f6b3504b2b1 upstream.
The ops->receive_buf() may be accessed concurrently from these two functions. If the driver flushes data to the line discipline receive_buf() method while tiocsti() is waiting for the ops->receive_buf() to finish its work, the data race will happen.
For example: tty_ioctl |tty_ldisc_receive_buf ->tioctsi | ->tty_port_default_receive_buf | ->tty_ldisc_receive_buf ->hci_uart_tty_receive | ->hci_uart_tty_receive ->h4_recv | ->h4_recv
In this case, the h4 receive buffer will be overwritten by the latecomer, and we will lost the data.
Hence, change tioctsi() function to use the exclusive lock interface from tty_buffer to avoid the data race.
Reported-by: syzbot+97388eb9d31b997fe1d0@syzkaller.appspotmail.com Reviewed-by: Jiri Slaby jirislaby@kernel.org Signed-off-by: Nguyen Dinh Phi phind.uet@gmail.com Link: https://lore.kernel.org/r/20210823000641.2082292-1-phind.uet@gmail.com Cc: stable stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Chen Jun chenjun102@huawei.com Acked-by: Weilong Chen chenweilong@huawei.com
Signed-off-by: Chen Jun chenjun102@huawei.com --- drivers/tty/tty_io.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index bc5314092aa4..669aef77a0bd 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -2257,8 +2257,6 @@ static int tty_fasync(int fd, struct file *filp, int on) * Locking: * Called functions take tty_ldiscs_lock * current->signal->tty check is safe without locks - * - * FIXME: may race normal receive processing */
static int tiocsti(struct tty_struct *tty, char __user *p) @@ -2274,8 +2272,10 @@ static int tiocsti(struct tty_struct *tty, char __user *p) ld = tty_ldisc_ref_wait(tty); if (!ld) return -EIO; + tty_buffer_lock_exclusive(tty->port); if (ld->ops->receive_buf) ld->ops->receive_buf(tty, &ch, &mbz, 1); + tty_buffer_unlock_exclusive(tty->port); tty_ldisc_deref(ld); return 0; }