From: Ingo Molnar <mingo@kernel.org> To: Toshi Kani <toshi.kani@hpe.com> Cc: mhocko@suse.com, akpm@linux-foundation.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, bp@suse.de, catalin.marinas@arm.com, guohanjun@huawei.com, will.deacon@arm.com, wxf.wang@hisilicon.com, linux-mm@kvack.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Andy Lutomirski <luto@kernel.org>, Linus Torvalds <torvalds@linux-foundation.org>, Peter Zijlstra <a.p.zijlstra@chello.nl> Subject: Re: [PATCH 1/2] mm/vmalloc: Add interfaces to free unused page table Date: Thu, 8 Mar 2018 09:08:47 +0100 [thread overview] Message-ID: <20180308080847.dvwd3w6wuhwsg3qo@gmail.com> (raw) In-Reply-To: <20180307183227.17983-2-toshi.kani@hpe.com> * Toshi Kani <toshi.kani@hpe.com> wrote: > On architectures with CONFIG_HAVE_ARCH_HUGE_VMAP set, ioremap() > may create pud/pmd mappings. Kernel panic was observed on arm64 > systems with Cortex-A75 in the following steps as described by > Hanjun Guo. > > 1. ioremap a 4K size, valid page table will build, > 2. iounmap it, pte0 will set to 0; > 3. ioremap the same address with 2M size, pgd/pmd is unchanged, > then set the a new value for pmd; > 4. pte0 is leaked; > 5. CPU may meet exception because the old pmd is still in TLB, > which will lead to kernel panic. > > This panic is not reproducible on x86. INVLPG, called from iounmap, > purges all levels of entries associated with purged address on x86. Where does x86 iounmap() do that? > x86 still has memory leak. > Add two interfaces, pud_free_pmd_page() and pmd_free_pte_page(), > which clear a given pud/pmd entry and free up a page for the lower > level entries. > > This patch implements their stub functions on x86 and arm64, which > work as workaround. At minimum the ordering of the patches is very confusing: why don't you introduce the new methods in patch #1, and then use them in patch #2? Also please double check the coding style of your patches, there's a number of obvious problems of outright bad patterns and also cases where you clearly don't try to follow the (correct) style of existing code. Thanks, Ingo
WARNING: multiple messages have this Message-ID (diff)
From: mingo@kernel.org (Ingo Molnar) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH 1/2] mm/vmalloc: Add interfaces to free unused page table Date: Thu, 8 Mar 2018 09:08:47 +0100 [thread overview] Message-ID: <20180308080847.dvwd3w6wuhwsg3qo@gmail.com> (raw) In-Reply-To: <20180307183227.17983-2-toshi.kani@hpe.com> * Toshi Kani <toshi.kani@hpe.com> wrote: > On architectures with CONFIG_HAVE_ARCH_HUGE_VMAP set, ioremap() > may create pud/pmd mappings. Kernel panic was observed on arm64 > systems with Cortex-A75 in the following steps as described by > Hanjun Guo. > > 1. ioremap a 4K size, valid page table will build, > 2. iounmap it, pte0 will set to 0; > 3. ioremap the same address with 2M size, pgd/pmd is unchanged, > then set the a new value for pmd; > 4. pte0 is leaked; > 5. CPU may meet exception because the old pmd is still in TLB, > which will lead to kernel panic. > > This panic is not reproducible on x86. INVLPG, called from iounmap, > purges all levels of entries associated with purged address on x86. Where does x86 iounmap() do that? > x86 still has memory leak. > Add two interfaces, pud_free_pmd_page() and pmd_free_pte_page(), > which clear a given pud/pmd entry and free up a page for the lower > level entries. > > This patch implements their stub functions on x86 and arm64, which > work as workaround. At minimum the ordering of the patches is very confusing: why don't you introduce the new methods in patch #1, and then use them in patch #2? Also please double check the coding style of your patches, there's a number of obvious problems of outright bad patterns and also cases where you clearly don't try to follow the (correct) style of existing code. Thanks, Ingo
next prev parent reply other threads:[~2018-03-08 8:08 UTC|newest] Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-03-07 18:32 [PATCH 0/2] fix memory leak / panic in ioremap huge pages Toshi Kani 2018-03-07 18:32 ` Toshi Kani 2018-03-07 18:32 ` Toshi Kani 2018-03-07 18:32 ` [PATCH 1/2] mm/vmalloc: Add interfaces to free unused page table Toshi Kani 2018-03-07 18:32 ` Toshi Kani 2018-03-07 18:32 ` Toshi Kani 2018-03-07 22:54 ` Andrew Morton 2018-03-07 22:54 ` Andrew Morton 2018-03-07 23:02 ` Kani, Toshi 2018-03-07 23:02 ` Kani, Toshi 2018-03-07 22:55 ` Andrew Morton 2018-03-07 22:55 ` Andrew Morton 2018-03-08 4:00 ` Matthew Wilcox 2018-03-08 4:00 ` Matthew Wilcox 2018-03-08 15:56 ` Kani, Toshi 2018-03-08 15:56 ` Kani, Toshi 2018-03-08 22:07 ` Matthew Wilcox 2018-03-08 22:07 ` Matthew Wilcox 2018-03-08 23:27 ` Kani, Toshi 2018-03-08 23:27 ` Kani, Toshi 2018-03-08 8:08 ` Ingo Molnar [this message] 2018-03-08 8:08 ` Ingo Molnar 2018-03-08 18:04 ` Will Deacon 2018-03-08 18:04 ` Will Deacon 2018-03-08 19:30 ` Kani, Toshi 2018-03-08 19:30 ` Kani, Toshi 2018-03-07 18:32 ` [PATCH 2/2] x86/mm: implement free pmd/pte page interfaces Toshi Kani 2018-03-07 18:32 ` Toshi Kani 2018-03-07 18:32 ` Toshi Kani 2018-03-07 23:01 ` Andrew Morton 2018-03-07 23:01 ` Andrew Morton 2018-03-07 23:22 ` Kani, Toshi 2018-03-07 23:22 ` Kani, Toshi
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