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1494e0c38e
Patch series "Fix W+X debug feature on x86" Jan alerted me[1] that the W+X detection debug feature was broken in x86 by my change[2] to switch x86 to use the generic ptdump infrastructure. Fundamentally the approach of trying to move the calculation of effective permissions into note_page() was broken because note_page() is only called for 'leaf' entries and the effective permissions are passed down via the internal nodes of the page tree. The solution I've taken here is to create a new (optional) callback which is called for all nodes of the page tree and therefore can calculate the effective permissions. Secondly on some configurations (32 bit with PAE) "unsigned long" is not large enough to store the table entries. The fix here is simple - let's just use a u64. [1] https://lore.kernel.org/lkml/d573dc7e-e742-84de-473d-f971142fa319@suse.com/ [2]2ae27137b2("x86: mm: convert dump_pagetables to use walk_page_range") This patch (of 2): By switching the x86 page table dump code to use the generic code the effective permissions are no longer calculated correctly because the note_page() function is only called for *leaf* entries. To calculate the actual effective permissions it is necessary to observe the full hierarchy of the page tree. Introduce a new callback for ptdump which is called for every entry and can therefore update the prot_levels array correctly. note_page() can then simply access the appropriate element in the array. [steven.price@arm.com: make the assignment conditional on val != 0] Link: http://lkml.kernel.org/r/430c8ab4-e7cd-6933-dde6-087fac6db872@arm.com Fixes:2ae27137b2("x86: mm: convert dump_pagetables to use walk_page_range") Reported-by: Jan Beulich <jbeulich@suse.com> Signed-off-by: Steven Price <steven.price@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Qian Cai <cai@lca.pw> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: <stable@vger.kernel.org> Link: http://lkml.kernel.org/r/20200521152308.33096-1-steven.price@arm.com Link: http://lkml.kernel.org/r/20200521152308.33096-2-steven.price@arm.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
155 lines
3.8 KiB
C
155 lines
3.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/pagewalk.h>
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#include <linux/ptdump.h>
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#include <linux/kasan.h>
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#ifdef CONFIG_KASAN
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/*
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* This is an optimization for KASAN=y case. Since all kasan page tables
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* eventually point to the kasan_early_shadow_page we could call note_page()
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* right away without walking through lower level page tables. This saves
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* us dozens of seconds (minutes for 5-level config) while checking for
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* W+X mapping or reading kernel_page_tables debugfs file.
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*/
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static inline int note_kasan_page_table(struct mm_walk *walk,
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unsigned long addr)
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{
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struct ptdump_state *st = walk->private;
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st->note_page(st, addr, 4, pte_val(kasan_early_shadow_pte[0]));
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walk->action = ACTION_CONTINUE;
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return 0;
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}
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#endif
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static int ptdump_pgd_entry(pgd_t *pgd, unsigned long addr,
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unsigned long next, struct mm_walk *walk)
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{
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struct ptdump_state *st = walk->private;
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pgd_t val = READ_ONCE(*pgd);
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#if CONFIG_PGTABLE_LEVELS > 4 && defined(CONFIG_KASAN)
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if (pgd_page(val) == virt_to_page(lm_alias(kasan_early_shadow_p4d)))
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return note_kasan_page_table(walk, addr);
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#endif
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if (st->effective_prot)
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st->effective_prot(st, 0, pgd_val(val));
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if (pgd_leaf(val))
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st->note_page(st, addr, 0, pgd_val(val));
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return 0;
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}
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static int ptdump_p4d_entry(p4d_t *p4d, unsigned long addr,
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unsigned long next, struct mm_walk *walk)
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{
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struct ptdump_state *st = walk->private;
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p4d_t val = READ_ONCE(*p4d);
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#if CONFIG_PGTABLE_LEVELS > 3 && defined(CONFIG_KASAN)
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if (p4d_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pud)))
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return note_kasan_page_table(walk, addr);
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#endif
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if (st->effective_prot)
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st->effective_prot(st, 1, p4d_val(val));
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if (p4d_leaf(val))
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st->note_page(st, addr, 1, p4d_val(val));
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return 0;
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}
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static int ptdump_pud_entry(pud_t *pud, unsigned long addr,
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unsigned long next, struct mm_walk *walk)
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{
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struct ptdump_state *st = walk->private;
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pud_t val = READ_ONCE(*pud);
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#if CONFIG_PGTABLE_LEVELS > 2 && defined(CONFIG_KASAN)
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if (pud_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pmd)))
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return note_kasan_page_table(walk, addr);
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#endif
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if (st->effective_prot)
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st->effective_prot(st, 2, pud_val(val));
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if (pud_leaf(val))
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st->note_page(st, addr, 2, pud_val(val));
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return 0;
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}
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static int ptdump_pmd_entry(pmd_t *pmd, unsigned long addr,
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unsigned long next, struct mm_walk *walk)
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{
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struct ptdump_state *st = walk->private;
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pmd_t val = READ_ONCE(*pmd);
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#if defined(CONFIG_KASAN)
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if (pmd_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pte)))
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return note_kasan_page_table(walk, addr);
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#endif
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if (st->effective_prot)
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st->effective_prot(st, 3, pmd_val(val));
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if (pmd_leaf(val))
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st->note_page(st, addr, 3, pmd_val(val));
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return 0;
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}
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static int ptdump_pte_entry(pte_t *pte, unsigned long addr,
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unsigned long next, struct mm_walk *walk)
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{
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struct ptdump_state *st = walk->private;
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pte_t val = READ_ONCE(*pte);
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if (st->effective_prot)
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st->effective_prot(st, 4, pte_val(val));
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st->note_page(st, addr, 4, pte_val(val));
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return 0;
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}
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static int ptdump_hole(unsigned long addr, unsigned long next,
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int depth, struct mm_walk *walk)
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{
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struct ptdump_state *st = walk->private;
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st->note_page(st, addr, depth, 0);
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return 0;
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}
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static const struct mm_walk_ops ptdump_ops = {
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.pgd_entry = ptdump_pgd_entry,
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.p4d_entry = ptdump_p4d_entry,
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.pud_entry = ptdump_pud_entry,
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.pmd_entry = ptdump_pmd_entry,
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.pte_entry = ptdump_pte_entry,
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.pte_hole = ptdump_hole,
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};
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void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd)
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{
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const struct ptdump_range *range = st->range;
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down_read(&mm->mmap_sem);
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while (range->start != range->end) {
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walk_page_range_novma(mm, range->start, range->end,
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&ptdump_ops, pgd, st);
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range++;
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}
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up_read(&mm->mmap_sem);
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/* Flush out the last page */
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st->note_page(st, 0, -1, 0);
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}
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