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tty: fix __tty_insert_flip_char regression

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commit 8a5a90a2a477b86a3dc2eaa5a706db9bfdd647ca upstream.

Sergey noticed a small but fatal mistake in __tty_insert_flip_char,
leading to an oops in an interrupt handler when using any serial
port.

The problem is that I accidentally took the tty_buffer pointer
before calling __tty_buffer_request_room(), which replaces the
buffer. This moves the pointer lookup to the right place after
allocating the new buffer space.

Fixes: 979990c62848 ("tty: improve tty_insert_flip_char() fast path")
Reported-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Arnd Bergmann 2017-08-02 13:11:39 +02:00 • committed by Greg Kroah-Hartman
parent 077933dcd5
commit c13c5c7e88
1 changed files with 2 additions and 1 deletions
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3
drivers/tty/tty_buffer.c
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@ -372,12 +372,13 @@ EXPORT_SYMBOL(tty_insert_flip_string_flags);
*/
int __tty_insert_flip_char(struct tty_port *port, unsigned char ch, char flag)
{
struct tty_buffer *tb = port->buf.tail;
struct tty_buffer *tb;
int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0;
if (!__tty_buffer_request_room(port, 1, flags))
return 0;
tb = port->buf.tail;
if (~tb->flags & TTYB_NORMAL)
*flag_buf_ptr(tb, tb->used) = flag;
*char_buf_ptr(tb, tb->used++) = ch;