Okash Khawaja a09ac3974d tty: resolve tty contention between kernel and user space ... The commit 12e84c71b7 ("tty: export tty_open_by_driver") exports tty_open_by_device to allow tty to be opened from inside kernel which works fine except that it doesn't handle contention with user space or another kernel-space open of the same tty. For example, opening a tty from user space while it is kernel opened results in failure and a kernel log message about mismatch between tty->count and tty's file open count. This patch makes kernel access to tty exclusive, so that if a user process or kernel opens a kernel opened tty, it gets -EBUSY. It does this by adding TTY_KOPENED flag to tty->flags. When this flag is set, tty_open_by_driver returns -EBUSY. Instead of overloading tty_open_by_driver for both kernel and user space, this patch creates a separate function tty_kopen which closely follows tty_open_by_driver. tty_kclose closes the tty opened by tty_kopen. To address the mismatch between tty->count and #fd's, this patch adds #kopen's to the count before comparing it with tty->count. That way check_tty_count reflects correct usage count. Returning -EBUSY on tty open is a change in the interface. I have tested this with minicom, picocom and commands like "echo foo > /dev/ttyS0". They all correctly report "Device or resource busy" when the tty is already kernel opened. Signed-off-by: Okash Khawaja <okash.khawaja@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2017-08-28 16:15:41 +02:00
..
acpi	ACPI: NUMA: add missing include in acpi_numa.h	2017-07-24 22:27:43 +02:00
asm-generic	Kbuild fixes for v4.13	2017-08-24 14:22:27 -07:00
clocksource
crypto
drm	i915, amd and some core fixes + mediatek color support	2017-07-13 11:26:18 -07:00
dt-bindings	Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus	2017-07-15 10:59:54 -07:00
keys
kvm	KVM: arm/arm64: PMU: Fix overflow interrupt injection	2017-07-25 14:18:01 +01:00
linux	tty: resolve tty contention between kernel and user space	2017-08-28 16:15:41 +02:00
math-emu
media	media: platform: davinci: drop VPFE_CMD_S_CCDC_RAW_PARAMS	2017-07-26 06:14:33 -04:00
memory
misc
net	net_sched: fix order of queue length updates in qdisc_replace()	2017-08-20 20:02:00 -07:00
pcmcia
ras
rdma	IB/core: Avoid accessing non-allocated memory when inferring port type	2017-08-24 15:33:33 -04:00
rxrpc
scsi	SCSI fixes on 20170823	2017-08-23 11:34:40 -07:00
soc	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next	2017-07-05 12:31:59 -07:00
sound	ASoC: fix pcm-creation regression	2017-07-17 15:50:32 +01:00
target	iscsi-target: Fix iscsi_np reset hung task during parallel delete	2017-08-06 14:41:41 -07:00
trace	ext4: remove unused metadata accounting variables	2017-07-30 22:30:11 -04:00
uapi	Revert "loop: support 4k physical blocksize"	2017-08-23 15:57:55 -06:00
video
xen	xen/balloon: don't online new memory initially	2017-07-23 08:13:18 +02:00