4.18-stable review patch. If anyone has any objections, please let me know.
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From: Johan Hovold johan@kernel.org
[ Upstream commit 1cee38f0363a88db374e50b232ca17b9a4c12fa0 ]
When the termios CIBAUD bits are left unset (i.e. B0), we use the same output and input speed and should leave CIBAUD unchanged.
When the user requests a rate using BOTHER and c_ospeed which the driver cannot set exactly, the driver can report back the actual baud rate using tty_termios_encode_baud_rate(). If this rate is close enough to a standard rate however, we could end up setting CIBAUD to a Bfoo value despite the user having left it unset.
This in turn could lead to an unexpected input rate being set on subsequent termios updates.
Fix this by using a zero tolerance value also for the input rate when CIBAUD is clear so that the matching logic works as expected.
Fixes: 78137e3b34e1 ("[PATCH] tty: improve encode_baud_rate logic") Signed-off-by: Johan Hovold johan@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/tty_baudrate.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
--- a/drivers/tty/tty_baudrate.c +++ b/drivers/tty/tty_baudrate.c @@ -157,16 +157,20 @@ void tty_termios_encode_baud_rate(struct termios->c_ospeed = obaud;
#ifdef BOTHER + if ((termios->c_cflag >> IBSHIFT) & CBAUD) + ibinput = 1; /* An input speed was specified */ + /* If the user asked for a precise weird speed give a precise weird answer. If they asked for a Bfoo speed they may have problems digesting non-exact replies so fuzz a bit */
- if ((termios->c_cflag & CBAUD) == BOTHER) + if ((termios->c_cflag & CBAUD) == BOTHER) { oclose = 0; + if (!ibinput) + iclose = 0; + } if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER) iclose = 0; - if ((termios->c_cflag >> IBSHIFT) & CBAUD) - ibinput = 1; /* An input speed was specified */ #endif termios->c_cflag &= ~CBAUD;