Linux-HyperV Archive on lore.kernel.org
 help / color / Atom feed
From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Boqun Feng <boqun.feng@gmail.com>,
	linux-hyperv@vger.kernel.org,
	Michael Kelley <mikelley@microsoft.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH AUTOSEL 5.4 336/459] clocksource/drivers/hyper-v: Reserve PAGE_SIZE space for tsc page
Date: Fri, 14 Feb 2020 10:59:46 -0500
Message-ID: <20200214160149.11681-336-sashal@kernel.org> (raw)
In-Reply-To: <20200214160149.11681-1-sashal@kernel.org>

From: Boqun Feng <boqun.feng@gmail.com>

[ Upstream commit ddc61bbc45017726a2b450350d476b4dc5ae25ce ]

Currently, the reserved size for a tsc page is 4K, which is enough for
communicating with hypervisor. However, in the case where we want to
export the tsc page to userspace (e.g. for vDSO to read the
clocksource), the tsc page should be at least PAGE_SIZE, otherwise, when
PAGE_SIZE is larger than 4K, extra kernel data will be mapped into
userspace, which means leaking kernel information.

Therefore reserve PAGE_SIZE space for tsc_pg as a preparation for the
vDSO support of ARM64 in the future. Also, while at it, replace all
reference to tsc_pg with hv_get_tsc_page() since it should be the only
interface to access tsc page.

Signed-off-by: Boqun Feng (Microsoft) <boqun.feng@gmail.com>
Cc: linux-hyperv@vger.kernel.org
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20191126021723.4710-1-boqun.feng@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/clocksource/hyperv_timer.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index 2317d4e3daaff..bcac936fa62bd 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -213,17 +213,20 @@ EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
 struct clocksource *hyperv_cs;
 EXPORT_SYMBOL_GPL(hyperv_cs);
 
-static struct ms_hyperv_tsc_page tsc_pg __aligned(PAGE_SIZE);
+static union {
+	struct ms_hyperv_tsc_page page;
+	u8 reserved[PAGE_SIZE];
+} tsc_pg __aligned(PAGE_SIZE);
 
 struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
 {
-	return &tsc_pg;
+	return &tsc_pg.page;
 }
 EXPORT_SYMBOL_GPL(hv_get_tsc_page);
 
 static u64 notrace read_hv_clock_tsc(struct clocksource *arg)
 {
-	u64 current_tick = hv_read_tsc_page(&tsc_pg);
+	u64 current_tick = hv_read_tsc_page(hv_get_tsc_page());
 
 	if (current_tick == U64_MAX)
 		hv_get_time_ref_count(current_tick);
@@ -278,7 +281,7 @@ static bool __init hv_init_tsc_clocksource(void)
 		return false;
 
 	hyperv_cs = &hyperv_cs_tsc;
-	phys_addr = virt_to_phys(&tsc_pg);
+	phys_addr = virt_to_phys(hv_get_tsc_page());
 
 	/*
 	 * The Hyper-V TLFS specifies to preserve the value of reserved
-- 
2.20.1


           reply index

Thread overview: expand[flat|nested]  mbox.gz  Atom feed
 [parent not found: <20200214160149.11681-1-sashal@kernel.org>]

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200214160149.11681-336-sashal@kernel.org \
    --to=sashal@kernel.org \
    --cc=boqun.feng@gmail.com \
    --cc=daniel.lezcano@linaro.org \
    --cc=linux-hyperv@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mikelley@microsoft.com \
    --cc=stable@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-HyperV Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-hyperv/0 linux-hyperv/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-hyperv linux-hyperv/ https://lore.kernel.org/linux-hyperv \
		linux-hyperv@vger.kernel.org
	public-inbox-index linux-hyperv

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-hyperv


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git