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tty: n_gsm: fix DM command

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[ Upstream commit 18a948c7d90995d127785e308fa7b701df4c499f ]

n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010.
See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516
The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to
the newer 27.010 here. Chapter 5.3.3 defines the DM response. There exists
no DM command. However, the current implementation incorrectly sends DM as
command in case of unexpected UIH frames in gsm_queue().
Correct this behavior by always sending DM as response.

Fixes: e1eaea46bb ("tty: n_gsm line discipline")
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220707113223.3685-2-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Daniel Starke 2022-07-07 13:32:21 +02:00 committed by Greg Kroah-Hartman
parent b625b74549
commit ae9bfcbfd7
1 changed files with 1 additions and 1 deletions
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drivers/tty/n_gsm.c
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@ -1894,7 +1894,7 @@ static void gsm_queue(struct gsm_mux *gsm)
goto invalid;
#endif
if (dlci == NULL || dlci->state != DLCI_OPEN) {
gsm_command(gsm, address, DM|PF);
gsm_response(gsm, address, DM|PF);
return;
}
dlci->data(dlci, gsm->buf, gsm->len);