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Johannes Weiner e65c62b137 tty: fall back to N_NULL if switching to N_TTY fails during hangup
We have seen NULL-pointer dereference crashes in tty->disc_data when the
N_TTY fallback driver failed to open during hangup.  The immediate cause
of this open to fail has been addressed in the preceding patch to
vmalloc(), but this code could be more robust.

As Alan pointed out in commit 8a8dabf2dd ("tty: handle the case where
we cannot restore a line discipline"), the N_TTY driver, historically
the safe fallback that could never fail, can indeed fail, but the
surrounding code is not prepared to handle this.  To avoid crashes he
added a new N_NULL driver to take N_TTY's place as the last resort.

Hook that fallback up to the hangup path.  Update tty_ldisc_reinit() to
reflect the reality that n_tty_open can indeed fail.

Link: http://lkml.kernel.org/r/20171004185959.GC2136@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Alan Cox <alan@llwyncelyn.cymru>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-10-13 16:18:33 -07:00
arch powerpc fixes for 4.14 #5 2017-10-13 11:39:28 -07:00
block bio_copy_user_iov(): don't ignore ->iov_offset 2017-10-10 23:55:14 -04:00
certs modsign: add markers to endif-statements in certs/Makefile 2017-07-14 11:01:37 +10:00
crypto crypto: shash - Fix zero-length shash ahash digest crash 2017-10-11 00:34:07 +08:00
Documentation Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-10-09 16:25:00 -07:00
drivers tty: fall back to N_NULL if switching to N_TTY fails during hangup 2017-10-13 16:18:33 -07:00
firmware firmware: Restore support for built-in firmware 2017-09-16 10:58:48 -07:00
fs Changes since last update: 2017-10-12 14:51:13 -07:00
include include/linux/of.h: provide of_n_{addr,size}_cells wrappers for !CONFIG_OF 2017-10-13 16:18:32 -07:00
init Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-09-14 18:54:01 -07:00
ipc fix a typo in put_compat_shm_info() 2017-09-25 20:41:46 -04:00
kernel Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching 2017-10-12 09:21:56 -07:00
lib lib/Kconfig.debug: kernel hacking menu: runtime testing: keep tests together 2017-10-13 16:18:32 -07:00
mm Revert "vmalloc: back off when the current task is killed" 2017-10-13 16:18:32 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-10-09 16:25:00 -07:00
samples media updates for v4.14-rc1 2017-09-07 12:53:14 -07:00
scripts scripts/kallsyms.c: ignore symbol type 'n' 2017-10-13 16:18:32 -07:00
security lsm: fix smack_inode_removexattr and xattr_getsecurity memleak 2017-10-04 18:03:15 +11:00
sound ALSA: caiaq: Fix stray URB at probe error path 2017-10-11 17:01:18 +02:00
tools userfaultfd: selftest: exercise -EEXIST only in background transfer 2017-10-13 16:18:32 -07:00
usr ramfs: clarify help text that compression applies to ramfs as well as legacy ramdisk. 2017-07-06 16:24:30 -07:00
virt Revert "KVM: Don't accept obviously wrong gsi values via KVM_IRQFD" 2017-09-19 08:37:17 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support to generate LLVM assembly files 2017-04-25 08:13:52 +09:00
.mailmap Update James Hogan's email address 2017-10-04 17:11:53 -07:00
COPYING
CREDITS selinux/stable-4.14 PR 20170831 2017-09-12 13:21:00 -07:00
Kbuild kbuild: Consolidate header generation from ASM offset information 2017-04-13 05:43:37 +09:00
Kconfig
MAINTAINERS Another latent bug related to PCID, an out-of-bounds access, 2017-10-12 10:42:03 -07:00
Makefile Linux 4.14-rc4 2017-10-08 20:53:29 -07:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.