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tty: Fix lookahead_buf crash with serdev

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Do not follow a NULL pointer if the tty_port_client_operations does not
implement the ->lookahead_buf() callback, which is the case with
serdev's ttyport.

Reported-by: Hans de Goede <hdegoede@redhat.com>
Fixes: 6bb6fa6908 ("tty: Implement lookahead to process XON/XOFF timely")
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Link: https://lore.kernel.org/r/20220818115026.2237893-1-vincent.whitchurch@axis.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Vincent Whitchurch 2022-08-18 13:50:26 +02:00 committed by Greg Kroah-Hartman
parent 846651eca0
commit 56c14fb408
1 changed files with 9 additions and 5 deletions
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14
drivers/tty/tty_buffer.c
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@ -470,7 +470,6 @@ static void lookahead_bufs(struct tty_port *port, struct tty_buffer *head)
while (head) {
struct tty_buffer *next;
unsigned char *p, *f = NULL;
unsigned int count;
/*
@ -489,11 +488,16 @@ static void lookahead_bufs(struct tty_port *port, struct tty_buffer *head)
continue;
}
p = char_buf_ptr(head, head->lookahead);
if (~head->flags & TTYB_NORMAL)
f = flag_buf_ptr(head, head->lookahead);
if (port->client_ops->lookahead_buf) {
unsigned char *p, *f = NULL;
p = char_buf_ptr(head, head->lookahead);
if (~head->flags & TTYB_NORMAL)
f = flag_buf_ptr(head, head->lookahead);
port->client_ops->lookahead_buf(port, p, f, count);
}
port->client_ops->lookahead_buf(port, p, f, count);
head->lookahead += count;
}
}