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[PATCH 4.13 010/109] tty: improve tty_insert_flip_char() fast path

From Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups linux.kernel
Subject [PATCH 4.13 010/109] tty: improve tty_insert_flip_char() fast path
Date 2017-09-24 23:10 +0200
Message-ID <utmk3-5jg-45@gated-at.bofh.it> (permalink)
References <utm0F-4Xd-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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4.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Arnd Bergmann <arnd@arndb.de>

commit 979990c6284814617d8f2179d197f72ff62b5d85 upstream.

kernelci.org reports a crazy stack usage for the VT code when CONFIG_KASAN
is enabled:

drivers/tty/vt/keyboard.c: In function 'kbd_keycode':
drivers/tty/vt/keyboard.c:1452:1: error: the frame size of 2240 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]

The problem is that tty_insert_flip_char() gets inlined many times into
kbd_keycode(), and also into other functions, and each copy requires 128
bytes for stack redzone to check for a possible out-of-bounds access on
the 'ch' and 'flags' arguments that are passed into
tty_insert_flip_string_flags as a variable-length string.

This introduces a new __tty_insert_flip_char() function for the slow
path, which receives the two arguments by value. This completely avoids
the problem and the stack usage goes back down to around 100 bytes.

Without KASAN, this is also slightly better, as we don't have to
spill the arguments to the stack but can simply pass 'ch' and 'flag'
in registers, saving a few bytes in .text for each call site.

This should be backported to linux-4.0 or later, which first introduced
the stack sanitizer in the kernel.

Fixes: c420f167db8c ("kasan: enable stack instrumentation")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/tty/tty_buffer.c |   24 ++++++++++++++++++++++++
 include/linux/tty_flip.h |    3 ++-
 2 files changed, 26 insertions(+), 1 deletion(-)

--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -362,6 +362,30 @@ int tty_insert_flip_string_flags(struct
 EXPORT_SYMBOL(tty_insert_flip_string_flags);
 
 /**
+ *	__tty_insert_flip_char   -	Add one character to the tty buffer
+ *	@port: tty port
+ *	@ch: character
+ *	@flag: flag byte
+ *
+ *	Queue a single byte to the tty buffering, with an optional flag.
+ *	This is the slow path of tty_insert_flip_char.
+ */
+int __tty_insert_flip_char(struct tty_port *port, unsigned char ch, char flag)
+{
+	struct tty_buffer *tb = port->buf.tail;
+	int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0;
+
+	if (!tty_buffer_request_room(port, 1))
+		return 0;
+
+	*flag_buf_ptr(tb, tb->used) = flag;
+	*char_buf_ptr(tb, tb->used++) = ch;
+
+	return 1;
+}
+EXPORT_SYMBOL(__tty_insert_flip_char);
+
+/**
  *	tty_schedule_flip	-	push characters to ldisc
  *	@port: tty port to push from
  *
--- a/include/linux/tty_flip.h
+++ b/include/linux/tty_flip.h
@@ -12,6 +12,7 @@ extern int tty_prepare_flip_string(struc
 		unsigned char **chars, size_t size);
 extern void tty_flip_buffer_push(struct tty_port *port);
 void tty_schedule_flip(struct tty_port *port);
+int __tty_insert_flip_char(struct tty_port *port, unsigned char ch, char flag);
 
 static inline int tty_insert_flip_char(struct tty_port *port,
 					unsigned char ch, char flag)
@@ -26,7 +27,7 @@ static inline int tty_insert_flip_char(s
 		*char_buf_ptr(tb, tb->used++) = ch;
 		return 1;
 	}
-	return tty_insert_flip_string_flags(port, &ch, &flag, 1);
+	return __tty_insert_flip_char(port, ch, flag);
 }
 
 static inline int tty_insert_flip_string(struct tty_port *port,

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[PATCH 4.13 000/109] 4.13.4-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 058/109] scsi: qedi: off by one in qedi_get_cmd_from_tid() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 041/109] powerpc/powernv/npu: Move tlb flush before launching ATSD Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 088/109] media: venus: fix copy/paste error in return_buf_error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 066/109] scsi: sg: fixup infoleak when using SG_GET_REQUEST_TABLE Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 031/109] crypto: scompress - dont sleep with preemption disabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 060/109] scsi: megaraid_sas: mismatch of allocated MFI frame size and length exposed in MFI MPT pass through command Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 039/109] ext4: fix quota inconsistency during orphan cleanup for read-only mounts Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 067/109] scsi: qla2xxx: Update fw_started flags at qpair creation. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 054/109] scsi: zfcp: fix missing trace records for early returns in TMF eh handlers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 083/109] net/netfilter/nf_conntrack_core: Fix net_conntrack_lock() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 028/109] MIPS: math-emu: <MADDF|MSUBF>.D: Fix accuracy (64-bit case) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 049/109] skd: Submit requests to firmware before triggering the doorbell Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 085/109] s390/mm: fix race on mm->context.flush_mm Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 062/109] scsi: megaraid_sas: Check valid aen class range to avoid kernel panic Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 036/109] wcn36xx: Introduce mutual exclusion of fw configuration Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 037/109] ext4: in ext4_seek_{hole,data}, return -ENXIO for negative offsets Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 078/109] tracing: Fix clear of RECORDED_TGID flag when disabling trace event Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 051/109] scsi: zfcp: add handling for FCP_RESID_OVER to the fcp ingress path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 059/109] scsi: aacraid: Fix command send race condition Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 027/109] MIPS: math-emu: <MADDF|MSUBF>.S: Fix accuracy (32-bit case) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 052/109] scsi: zfcp: fix capping of unsuccessful GPN_FT SAN response trace records Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 079/109] tracing: Apply trace_clock changes to instance max buffer Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 055/109] scsi: zfcp: fix payload with full FCP_RSP IU in SCSI trace records Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 026/109] MIPS: math-emu: <MADDF|MSUBF>.<D|S>: Clean up "maddf_flags" enumeration Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 029/109] docs: disable KASLR when debugging kernel Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 043/109] powerpc: Fix DAR reporting when alignment handler faults Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 046/109] md/bitmap: copy correct data for bitmap super Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 075/109] ftrace: Fix selftest goto location on error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 081/109] PCI: shpchp: Enable bridge bus mastering if MSI is enabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:00 +0200
  [PATCH 4.13 018/109] MIPS: math-emu: <MAX|MAXA|MIN|MINA>.<D|S>: Fix cases of both inputs zero Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
  [PATCH 4.13 024/109] MIPS: math-emu: <MADDF|MSUBF>.<D|S>: Fix some cases of infinite inputs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
  [PATCH 4.13 016/109] Input: i8042 - add Gigabyte P57 to the keyboard reset table Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
  [PATCH 4.13 008/109] Input: xpad - validate USB endpoint type during probe Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
  [PATCH 4.13 020/109] MIPS: math-emu: <MAXA|MINA>.<D|S>: Fix cases of input values with opposite signs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
  [PATCH 4.13 023/109] MIPS: math-emu: <MADDF|MSUBF>.<D|S>: Fix NaN propagation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
  [PATCH 4.13 009/109] drm/amdgpu: read reg in each iterator of psp_wait_for loop Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
  [PATCH 4.13 010/109] tty: improve tty_insert_flip_char() fast path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
  [PATCH 4.13 014/109] pinctrl: samsung: Fix NULL pointer exception on external interrupts on S3C24xx Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
  [PATCH 4.13 022/109] MIPS: math-emu: MINA.<D|S>: Fix some cases of infinity and zero inputs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
  [PATCH 4.13 011/109] tty: improve tty_insert_flip_char() slow path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
  [PATCH 4.13 019/109] MIPS: math-emu: <MAX|MIN>.<D|S>: Fix cases of both inputs negative Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
  [PATCH 4.13 001/109] orangefs: Dont clear SGID when inheriting ACLs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
    Re: [PATCH 4.13 001/109] orangefs: Dont clear SGID when inheriting ACLs Mike Marshall <hubcap@omnibond.com> - 2017-09-26 02:10 +0200
  [PATCH 4.13 004/109] IB/{qib, hfi1}: Avoid flow control testing for RDMA write operation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
  [PATCH 4.13 006/109] srcu: Provide ordering for CPU not involved in grace period Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
  [PATCH 4.13 017/109] MIPS: math-emu: <MAX|MAXA|MIN|MINA>.<D|S>: Fix quiet NaN propagation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-24 23:10 +0200
  Re: [PATCH 4.13 000/109] 4.13.4-stable review Guenter Roeck <linux@roeck-us.net> - 2017-09-25 03:10 +0200
    Re: [PATCH 4.13 000/109] 4.13.4-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-25 08:40 +0200
  Re: [PATCH 4.13 000/109] 4.13.4-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-09-26 01:20 +0200
    Re: [PATCH 4.13 000/109] 4.13.4-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-26 09:40 +0200

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