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Message-ID: <20180409001637.162453-153-alexander.levin@microsoft.com> Date: Mon, 9 Apr 2018 00:18:51 +0000 From: Sasha Levin <Alexander.Levin@...rosoft.com> To: "stable@...r.kernel.org" <stable@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> CC: Ross Lagerwall <ross.lagerwall@...rix.com>, Juergen Gross <jgross@...e.com>, Sasha Levin <Alexander.Levin@...rosoft.com> Subject: [PATCH AUTOSEL for 4.15 153/189] xen/grant-table: Use put_page instead of free_page From: Ross Lagerwall <ross.lagerwall@...rix.com> [ Upstream commit 3ac7292a25db1c607a50752055a18aba32ac2176 ] The page given to gnttab_end_foreign_access() to free could be a compound page so use put_page() instead of free_page() since it can handle both compound and single pages correctly. This bug was discovered when migrating a Xen VM with several VIFs and CONFIG_DEBUG_VM enabled. It hits a BUG usually after fewer than 10 iterations. All netfront devices disconnect from the backend during a suspend/resume and this will call gnttab_end_foreign_access() if a netfront queue has an outstanding skb. The mismatch between calling get_page() and free_page() on a compound page causes a reference counting error which is detected when DEBUG_VM is enabled. Signed-off-by: Ross Lagerwall <ross.lagerwall@...rix.com> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com> Signed-off-by: Juergen Gross <jgross@...e.com> Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com> --- drivers/xen/grant-table.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c index f45114fd8e1e..27be107d6480 100644 --- a/drivers/xen/grant-table.c +++ b/drivers/xen/grant-table.c @@ -382,7 +382,7 @@ static void gnttab_handle_deferred(struct timer_list *unused) if (entry->page) { pr_debug("freeing g.e. %#x (pfn %#lx)\n", entry->ref, page_to_pfn(entry->page)); - __free_page(entry->page); + put_page(entry->page); } else pr_info("freeing g.e. %#x\n", entry->ref); kfree(entry); @@ -438,7 +438,7 @@ void gnttab_end_foreign_access(grant_ref_t ref, int readonly, if (gnttab_end_foreign_access_ref(ref, readonly)) { put_free_entry(ref); if (page != 0) - free_page(page); + put_page(virt_to_page(page)); } else gnttab_add_deferred(ref, readonly, page ? virt_to_page(page) : NULL); -- 2.15.1
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