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| author | Alan Cox <alan@llwyncelyn.cymru> | 2017-06-02 13:49:30 +0100 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2018-10-21 08:45:38 +0100 |
| commit | a6a35a2a03c2fecc1d6dbf552a262fa7321b7adf (patch) | |
| tree | a61123466c8fa4f67fd118d7ec0e7daaec8076a8 /include | |
| parent | 2d377a2199617414a0599f8fe512b42a4967bdc3 (diff) | |
| download | linux-stable-a6a35a2a03c2fecc1d6dbf552a262fa7321b7adf.tar.gz linux-stable-a6a35a2a03c2fecc1d6dbf552a262fa7321b7adf.tar.bz2 linux-stable-a6a35a2a03c2fecc1d6dbf552a262fa7321b7adf.zip | |
tty: handle the case where we cannot restore a line discipline
commit 8a8dabf2dd68caff842d38057097c23bc514ea6e upstream.
Historically the N_TTY driver could never fail but this has become broken over
time. Rather than trying to rewrite half the ldisc layer to fix the breakage
introduce a second level of fallback with an N_NULL ldisc which cannot fail,
and thus restore the guarantees required by the ldisc layer.
We still try and fail to N_TTY first. It's much more useful to find yourself
back in your old ldisc (first attempt) or in N_TTY (second attempt), and while
I'm not aware of any code out there that makes those assumptions it's good to
drive(r) defensively.
Signed-off-by: Alan Cox <alan@linux.intel.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'include')
| -rw-r--r-- | include/uapi/linux/tty.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/uapi/linux/tty.h b/include/uapi/linux/tty.h index dac199a2dba5..512892743489 100644 --- a/include/uapi/linux/tty.h +++ b/include/uapi/linux/tty.h @@ -34,5 +34,6 @@ #define N_TI_WL 22 /* for TI's WL BT, FM, GPS combo chips */ #define N_TRACESINK 23 /* Trace data routing for MIPI P1149.7 */ #define N_TRACEROUTER 24 /* Trace data routing for MIPI P1149.7 */ +#define N_NULL 27 /* Null ldisc used for error handling */ #endif /* _UAPI_LINUX_TTY_H */ |