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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Xiaoming Gao <newtongao@tencent.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	peterz@infradead.org, hpa@zytor.com
Subject: [PATCH 3.18 02/24] x86/tsc: Prevent 32bit truncation in calc_hpet_ref()
Date: Fri, 27 Apr 2018 15:57:37 +0200	[thread overview]
Message-ID: <20180427135631.684181554@linuxfoundation.org> (raw)
In-Reply-To: <20180427135631.584839868@linuxfoundation.org>

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

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

From: Xiaoming Gao <gxm.linux.kernel@gmail.com>

commit d3878e164dcd3925a237a20e879432400e369172 upstream.

The TSC calibration code uses HPET as reference. The conversion normalizes
the delta of two HPET timestamps:

    hpetref = ((tshpet1 - tshpet2) * HPET_PERIOD) / 1e6

and then divides the normalized delta of the corresponding TSC timestamps
by the result to calulate the TSC frequency.

    tscfreq = ((tstsc1 - tstsc2 ) * 1e6) / hpetref

This uses do_div() which takes an u32 as the divisor, which worked so far
because the HPET frequency was low enough that 'hpetref' never exceeded
32bit.

On Skylake machines the HPET frequency increased so 'hpetref' can exceed
32bit. do_div() truncates the divisor, which causes the calibration to
fail.

Use div64_u64() to avoid the problem.

[ tglx: Fixes whitespace mangled patch and rewrote changelog ]

Signed-off-by: Xiaoming Gao <newtongao@tencent.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Cc: peterz@infradead.org
Cc: hpa@zytor.com
Link: https://lkml.kernel.org/r/38894564-4fc9-b8ec-353f-de702839e44e@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/kernel/tsc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -399,7 +399,7 @@ static unsigned long calc_hpet_ref(u64 d
 	hpet2 -= hpet1;
 	tmp = ((u64)hpet2 * hpet_readl(HPET_PERIOD));
 	do_div(tmp, 1000000);
-	do_div(deltatsc, tmp);
+	deltatsc = div64_u64(deltatsc, tmp);
 
 	return (unsigned long) deltatsc;
 }

  parent reply	other threads:[~2018-04-27 13:57 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-27 13:57 [PATCH 3.18 00/24] 3.18.107-stable review Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 01/24] cifs: do not allow creating sockets except with SMB1 posix exensions Greg Kroah-Hartman
2018-04-27 13:57 ` Greg Kroah-Hartman [this message]
2018-04-27 13:57 ` [PATCH 3.18 03/24] ext4: fix deadlock between inline_data and ext4_expand_extra_isize_ea() Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 04/24] ext4: bugfix for mmaped pages in mpage_release_unused_pages() Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 05/24] ext4: dont update checksum of new initialized bitmaps Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 06/24] perf: Return proper values for user stack errors Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 07/24] mm/filemap.c: fix NULL pointer in page_cache_tree_insert() Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 08/24] jbd2: fix use after free in kjournald2() Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 09/24] bonding: do not set slave_dev npinfo before slave_enable_netpoll in bond_enslave Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 10/24] KEYS: DNS: limit the length of option strings Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 11/24] l2tp: check sockaddr length in pppol2tp_connect() Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 12/24] tcp: dont read out-of-bounds opsize Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 13/24] team: avoid adding twice the same option to the event list Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 14/24] team: fix netconsole setup over team Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 15/24] pppoe: check sockaddr length in pppoe_connect() Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 16/24] llc: hold llc_sap before release_sock() Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 17/24] llc: fix NULL pointer deref for SOCK_ZAPPED Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 18/24] packet: fix bitfield update race Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 19/24] tcp: md5: reject TCP_MD5SIG or TCP_MD5SIG_EXT on established sockets Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 20/24] net: af_packet: fix race in PACKET_{R|T}X_RING Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 21/24] llc: delete timers synchronously in llc_sk_free() Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 22/24] ipv6: add RTA_TABLE and RTA_PREFSRC to rtm_ipv6_policy Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 23/24] scsi: mptsas: Disable WRITE SAME Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 24/24] cdrom: information leak in cdrom_ioctl_media_changed() Greg Kroah-Hartman
2018-04-27 16:00 ` [PATCH 3.18 00/24] 3.18.107-stable review Dede Dindin Qudsy
2018-04-28  5:51   ` Greg Kroah-Hartman
2018-04-28  6:40     ` Harsh Shandilya
2018-04-27 18:12 ` Shuah Khan
2018-04-28  5:02   ` Greg Kroah-Hartman
2018-04-27 19:03 ` kernelci.org bot
2018-04-27 19:41 ` Theodore Y. Ts'o
2018-04-28  4:35   ` Greg Kroah-Hartman
2018-04-27 21:33 ` Harsh Shandilya
2018-04-28  5:02   ` Greg Kroah-Hartman
2018-04-28 14:24 ` Guenter Roeck

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