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d="scan'208";a="12479583" From: Sergey Dyasli To: , , , CC: Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Boris Ostrovsky , Juergen Gross , "Stefano Stabellini" , George Dunlap , Ross Lagerwall , Andrew Morton , Sergey Dyasli Subject: [PATCH v3 1/4] kasan: introduce set_pmd_early_shadow() Date: Fri, 7 Feb 2020 14:26:49 +0000 Message-ID: <20200207142652.670-2-sergey.dyasli@citrix.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200207142652.670-1-sergey.dyasli@citrix.com> References: <20200207142652.670-1-sergey.dyasli@citrix.com> MIME-Version: 1.0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: It is incorrect to call pmd_populate_kernel() multiple times for the same page table from inside Xen PV domains. Xen notices it during kasan_populate_early_shadow(): (XEN) mm.c:3222:d155v0 mfn 3704b already pinned This happens for kasan_early_shadow_pte when USE_SPLIT_PTE_PTLOCKS is enabled. Fix this by introducing set_pmd_early_shadow() which calls pmd_populate_kernel() only once and uses set_pmd() afterwards. Signed-off-by: Sergey Dyasli --- v2 --> v3: no changes v1 --> v2: - Fix compilation without CONFIG_XEN_PV - Slightly updated description RFC --> v1: - New patch --- mm/kasan/init.c | 32 ++++++++++++++++++++++++-------- 1 file changed, 24 insertions(+), 8 deletions(-) diff --git a/mm/kasan/init.c b/mm/kasan/init.c index ce45c491ebcd..7791fe0a7704 100644 --- a/mm/kasan/init.c +++ b/mm/kasan/init.c @@ -81,6 +81,26 @@ static inline bool kasan_early_shadow_page_entry(pte_t pte) return pte_page(pte) == virt_to_page(lm_alias(kasan_early_shadow_page)); } +#ifdef CONFIG_XEN_PV +static inline void set_pmd_early_shadow(pmd_t *pmd) +{ + static bool pmd_populated = false; + pte_t *early_shadow = lm_alias(kasan_early_shadow_pte); + + if (likely(pmd_populated)) { + set_pmd(pmd, __pmd(__pa(early_shadow) | _PAGE_TABLE)); + } else { + pmd_populate_kernel(&init_mm, pmd, early_shadow); + pmd_populated = true; + } +} +#else +static inline void set_pmd_early_shadow(pmd_t *pmd) +{ + pmd_populate_kernel(&init_mm, pmd, lm_alias(kasan_early_shadow_pte)); +} +#endif /* ifdef CONFIG_XEN_PV */ + static __init void *early_alloc(size_t size, int node) { void *ptr = memblock_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS), @@ -120,8 +140,7 @@ static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr, next = pmd_addr_end(addr, end); if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) { - pmd_populate_kernel(&init_mm, pmd, - lm_alias(kasan_early_shadow_pte)); + set_pmd_early_shadow(pmd); continue; } @@ -157,8 +176,7 @@ static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr, pud_populate(&init_mm, pud, lm_alias(kasan_early_shadow_pmd)); pmd = pmd_offset(pud, addr); - pmd_populate_kernel(&init_mm, pmd, - lm_alias(kasan_early_shadow_pte)); + set_pmd_early_shadow(pmd); continue; } @@ -198,8 +216,7 @@ static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr, pud_populate(&init_mm, pud, lm_alias(kasan_early_shadow_pmd)); pmd = pmd_offset(pud, addr); - pmd_populate_kernel(&init_mm, pmd, - lm_alias(kasan_early_shadow_pte)); + set_pmd_early_shadow(pmd); continue; } @@ -271,8 +288,7 @@ int __ref kasan_populate_early_shadow(const void *shadow_start, pud_populate(&init_mm, pud, lm_alias(kasan_early_shadow_pmd)); pmd = pmd_offset(pud, addr); - pmd_populate_kernel(&init_mm, pmd, - lm_alias(kasan_early_shadow_pte)); + set_pmd_early_shadow(pmd); continue; }