[PATCH 3.12 66/86] tty: nozomi: avoid a harmless gcc warning

From	Jiri Slaby <jslaby@suse.cz>
Newsgroups	linux.kernel
Subject	[PATCH 3.12 66/86] tty: nozomi: avoid a harmless gcc warning
Date	2017-05-04 11:20 +0200
Message-ID	<tDl5w-1sT-19@gated-at.bofh.it> (permalink)
References	<tDkVQ-1oS-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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From: Arnd Bergmann <arnd@arndb.de>

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

===============

commit a4f642a8a3c2838ad09fe8313d45db46600e1478 upstream.

The nozomi wireless data driver has its own helper function to
transfer data from a FIFO, doing an extra byte swap on big-endian
architectures, presumably to bring the data back into byte-serial
order after readw() or readl() perform their implicit byteswap.

This helper function is used in the receive_data() function to
first read the length into a 32-bit variable, which causes
a compile-time warning:

drivers/tty/nozomi.c: In function 'receive_data':
drivers/tty/nozomi.c:857:9: warning: 'size' may be used uninitialized in this function [-Wmaybe-uninitialized]

The problem is that gcc is unsure whether the data was actually
read or not. We know that it is at this point, so we can replace
it with a single readl() to shut up that warning.

I am leaving the byteswap in there, to preserve the existing
behavior, even though this seems fishy: Reading the length of
the data into a cpu-endian variable should normally not use
a second byteswap on big-endian systems, unless the hardware
is aware of the CPU endianess.

There appears to be a lot more confusion about endianess in this
driver, so it probably has not worked on big-endian systems in
a long time, if ever, and I have no way to test it. It's well
possible that this driver has not been used by anyone in a while,
the last patch that looks like it was tested on the hardware is
from 2008.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/tty/nozomi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/nozomi.c b/drivers/tty/nozomi.c
index d6080c3831ef..ce2e5d508fe7 100644
--- a/drivers/tty/nozomi.c
+++ b/drivers/tty/nozomi.c
@@ -823,7 +823,7 @@ static int receive_data(enum port_type index, struct nozomi *dc)
 	struct tty_struct *tty = tty_port_tty_get(&port->port);
 	int i, ret;
 
-	read_mem32((u32 *) &size, addr, 4);
+	size = __le32_to_cpu(readl(addr));
 	/*  DBG1( "%d bytes port: %d", size, index); */
 
 	if (tty && test_bit(TTY_THROTTLED, &tty->flags)) {
-- 
2.12.2

Thread

[PATCH 3.12 00/86] 3.12.74-stable review Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
  [PATCH 3.12 01/86] drm/vmwgfx: NULL pointer dereference in vmw_surface_define_ioctl() Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 04/86] drm/vmwgfx: fix integer overflow in vmw_surface_define_ioctl() Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 81/86] ALSA: seq: Don't break snd_use_lock_sync() loop by timeout Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 25/86] perf/x86: Avoid exposing wrong/stale data in intel_pmu_lbr_read_32() Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 03/86] drm/vmwgfx: Remove getparam error message Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 05/86] Reset TreeId to zero on SMB2 TREE_CONNECT Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 85/86] nfsd: check for oversized NFSv2/v3 arguments Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 59/86] kvm: arm/arm64: Fix locking for kvm_free_stage2_pgd Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 26/86] x86/vdso: Plug race between mapping and ELF header setup Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 82/86] MIPS: KGDB: Use kernel context for sleeping threads Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 31/86] xen, fbfront: fix connecting to backend Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 56/86] ACPI / power: Avoid maybe-uninitialized warning Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 78/86] MIPS: Fix crash registers on non-crashing CPUs Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 28/86] iscsi-target: Drop work-around for legacy GlobalSAN initiator Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 29/86] scsi: sr: Sanity check returned mode data Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 83/86] p9_client_readdir() fix Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 06/86] ptrace: fix PTRACE_LISTEN race corrupting task->state Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 80/86] xen/x86: don't lose event interrupts Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 55/86] Input: elantech - add Fujitsu Lifebook E547 to force crc_enabled Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:10 +0200
    [PATCH 3.12 77/86] md:raid1: fix a dead loop when read from a WriteMostly disk Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 63/86] net/packet: fix overflow in check for tp_frame_nr Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 72/86] net: ipv4: fix multipath RTM_GETROUTE behavior when iif is given Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 61/86] powerpc: Reject binutils 2.24 when building little endian Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 75/86] ipv6: check raw payload size correctly in ioctl Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 60/86] block: fix del_gendisk() vs blkdev_ioctl crash Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 33/86] char: lack of bool string made CONFIG_DEVPORT always on Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 74/86] ip6mr: fix notification device destruction Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 66/86] tty: nozomi: avoid a harmless gcc warning Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 67/86] hostap: avoid uninitialized variable use in hfa384x_get_rid Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 64/86] net/packet: fix overflow in check for tp_reserve Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 76/86] ext4: check if in-inode xattr is corrupted in ext4_expand_extra_isize_ea() Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 45/86] net: ipv6: check route protocol when deleting routes Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 46/86] KEYS: Disallow keyrings beginning with '.' to be joined as session keyrings Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 65/86] netfilter: arp_tables: fix invoking 32bit "iptable -P INPUT ACCEPT" failed in 64bit kernel Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 42/86] rtl8150: Use heap buffers for all register access Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 30/86] scsi: sd: Fix capacity calculation with 32-bit sector_t Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 39/86] mm: Tighten x86 /dev/mem with zeroing reads Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 43/86] catc: Combine failure cleanup code in catc_probe() Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 51/86] cifs: Do not send echoes before Negotiate is complete Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 40/86] virtio-console: avoid DMA from stack Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 69/86] net: neigh: guard against NULL solicit() method Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 49/86] tracing: Allocate the snapshot buffer before enabling probe Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 50/86] ring-buffer: Have ring_buffer_iter_empty() return true when empty Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 53/86] Drivers: hv: don't leak memory in vmbus_establish_gpadl() Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 62/86] ping: implement proper locking Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 79/86] RDS: Fix the atomicity for congestion map update Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 84/86] Input: i8042 - add Clevo P650RS to the i8042 reset list Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 52/86] CIFS: remove bad_network_name flag Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 54/86] Drivers: hv: get rid of timeout in vmbus_open() Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 47/86] KEYS: Change the name of the dead type to ".dead" to prevent user access Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 41/86] pegasus: Use heap buffers for all register access Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 37/86] ext4: fix inode checksum calculation problem if i_extra_size is small Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 38/86] platform/x86: acer-wmi: setup accelerometer when machine has appropriate notify event Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 71/86] l2tp: take reference on sessions being dumped Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 68/86] gfs2: avoid uninitialized variable warning Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 70/86] net: phy: handle state correctly in phy_stop_machine Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 58/86] x86/mce/AMD: Give a name to MCA bank 3 when accessed with legacy MSRs Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 73/86] sctp: listen on the sock only when it's state is listening or closed Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:20 +0200
    [PATCH 3.12 18/86] usb: dwc3: gadget: delay unmap of bounced requests Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 32/86] char: Drop bogus dependency of DEVPORT on !M68K Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 36/86] dvb-usb-v2: avoid use-after-free Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 14/86] metag/usercopy: Add missing fixups Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 10/86] metag/usercopy: Add early abort to copy_to_user Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 21/86] usb: hub: Wait for connection to be reestablished after port reset Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 13/86] metag/usercopy: Fix src fixup in from user rapf loops Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 23/86] net/mlx4_core: Fix racy CQ (Completion Queue) free Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 34/86] zram: do not use copy_page with non-page aligned address Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 19/86] mtd: bcm47xxpart: fix parsing first block after aligned TRX Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 16/86] s390/decompressor: fix initrd corruption caused by bss clear Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 08/86] metag/usercopy: Drop unused macros Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 24/86] Input: xpad - add support for Razer Wildcat gamepad Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 44/86] catc: Use heap buffer for memory size test Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 35/86] powerpc: Disable HFSCR[TM] if TM is not supported Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 15/86] powerpc: Don't try to fix up misaligned load-with-reservation instructions Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 07/86] ring-buffer: Fix return value check in test_ringbuffer() Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 17/86] mm/mempolicy.c: fix error handling in set_mempolicy and mbind. Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 09/86] metag/usercopy: Fix alignment error checking Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 22/86] net/mlx4_en: Fix bad WQE issue Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 20/86] net/packet: fix overflow in check for priv area size Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 12/86] metag/usercopy: Set flags before ADDZ Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
    [PATCH 3.12 11/86] metag/usercopy: Zero rest of buffer from copy_from_user Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
  Re: [PATCH 3.12 00/86] 3.12.74-stable review Jiri Slaby <jslaby@suse.cz> - 2017-05-04 11:30 +0200
  Re: [PATCH 3.12 00/86] 3.12.74-stable review Guenter Roeck <linux@roeck-us.net> - 2017-05-04 18:00 +0200
    Re: [PATCH 3.12 00/86] 3.12.74-stable review Jiri Slaby <jslaby@suse.cz> - 2017-05-09 21:00 +0200
  Re: [PATCH 3.12 00/86] 3.12.74-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-05-04 21:00 +0200

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