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authorToshi Kani <toshi.kani@hpe.com>2018-03-22 16:17:20 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-03-28 18:40:14 +0200
commit31895cfd79564111cdd5a9f48c5d491ae26a238e (patch)
tree255d9a525fc1978c35069a5997be70d7cde698a8 /lib
parentfc0d81cf45b3d8215c1d10079ee73365d79b5555 (diff)
mm/vmalloc: add interfaces to free unmapped page table
commit b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e upstream. On architectures with CONFIG_HAVE_ARCH_HUGE_VMAP set, ioremap() may create pud/pmd mappings. A 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. x86 still has memory leak. The patch changes the ioremap path to free unmapped page table(s) since doing so in the unmap path has the following issues: - The iounmap() path is shared with vunmap(). Since vmap() only supports pte mappings, making vunmap() to free a pte page is an overhead for regular vmap users as they do not need a pte page freed up. - Checking if all entries in a pte page are cleared in the unmap path is racy, and serializing this check is expensive. - The unmap path calls free_vmap_area_noflush() to do lazy TLB purges. Clearing a pud/pmd entry before the lazy TLB purges needs extra TLB purge. 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. [akpm@linux-foundation.org: fix typo in pmd_free_pte_page() stub] Link: http://lkml.kernel.org/r/20180314180155.19492-2-toshi.kani@hpe.com Fixes: e61ce6ade404e ("mm: change ioremap to set up huge I/O mappings") Reported-by: Lei Li <lious.lilei@hisilicon.com> Signed-off-by: Toshi Kani <toshi.kani@hpe.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Wang Xuefeng <wxf.wang@hisilicon.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Hanjun Guo <guohanjun@huawei.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Borislav Petkov <bp@suse.de> Cc: Matthew Wilcox <willy@infradead.org> Cc: Chintan Pandya <cpandya@codeaurora.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> [ tweak arm64 portion to rely on CONFIG_ARCH_HAVE_HUGE_VMAP - gregkh] Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/ioremap.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/lib/ioremap.c b/lib/ioremap.c
index 86c8911b0e3a..5323b59ca393 100644
--- a/lib/ioremap.c
+++ b/lib/ioremap.c
@@ -83,7 +83,8 @@ static inline int ioremap_pmd_range(pud_t *pud, unsigned long addr,
if (ioremap_pmd_enabled() &&
((next - addr) == PMD_SIZE) &&
- IS_ALIGNED(phys_addr + addr, PMD_SIZE)) {
+ IS_ALIGNED(phys_addr + addr, PMD_SIZE) &&
+ pmd_free_pte_page(pmd)) {
if (pmd_set_huge(pmd, phys_addr + addr, prot))
continue;
}
@@ -109,7 +110,8 @@ static inline int ioremap_pud_range(pgd_t *pgd, unsigned long addr,
if (ioremap_pud_enabled() &&
((next - addr) == PUD_SIZE) &&
- IS_ALIGNED(phys_addr + addr, PUD_SIZE)) {
+ IS_ALIGNED(phys_addr + addr, PUD_SIZE) &&
+ pud_free_pmd_page(pud)) {
if (pud_set_huge(pud, phys_addr + addr, prot))
continue;
}