]>
Commit | Line | Data |
---|---|---|
321d628a FG |
1 | From bcb5ffbfba8c6c557ad536eb9084040b8e52923e Mon Sep 17 00:00:00 2001 |
2 | From: Andy Lutomirski <luto@kernel.org> | |
3 | Date: Mon, 4 Dec 2017 15:07:42 +0100 | |
e4cdf2a5 | 4 | Subject: [PATCH 196/241] x86/mm/pti: Add functions to clone kernel PMDs |
321d628a FG |
5 | MIME-Version: 1.0 |
6 | Content-Type: text/plain; charset=UTF-8 | |
7 | Content-Transfer-Encoding: 8bit | |
8 | ||
9 | CVE-2017-5754 | |
10 | ||
11 | Provide infrastructure to: | |
12 | ||
13 | - find a kernel PMD for a mapping which must be visible to user space for | |
14 | the entry/exit code to work. | |
15 | ||
16 | - walk an address range and share the kernel PMD with it. | |
17 | ||
18 | This reuses a small part of the original KAISER patches to populate the | |
19 | user space page table. | |
20 | ||
21 | [ tglx: Made it universally usable so it can be used for any kind of shared | |
22 | mapping. Add a mechanism to clear specific bits in the user space | |
23 | visible PMD entry. Folded Andys simplifactions ] | |
24 | ||
25 | Originally-by: Dave Hansen <dave.hansen@linux.intel.com> | |
26 | Signed-off-by: Andy Lutomirski <luto@kernel.org> | |
27 | Signed-off-by: Thomas Gleixner <tglx@linutronix.de> | |
28 | Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> | |
29 | Cc: Borislav Petkov <bp@alien8.de> | |
30 | Cc: Borislav Petkov <bpetkov@suse.de> | |
31 | Cc: Brian Gerst <brgerst@gmail.com> | |
32 | Cc: Dave Hansen <dave.hansen@linux.intel.com> | |
33 | Cc: David Laight <David.Laight@aculab.com> | |
34 | Cc: Denys Vlasenko <dvlasenk@redhat.com> | |
35 | Cc: Eduardo Valentin <eduval@amazon.com> | |
36 | Cc: Greg KH <gregkh@linuxfoundation.org> | |
37 | Cc: H. Peter Anvin <hpa@zytor.com> | |
38 | Cc: Josh Poimboeuf <jpoimboe@redhat.com> | |
39 | Cc: Juergen Gross <jgross@suse.com> | |
40 | Cc: Linus Torvalds <torvalds@linux-foundation.org> | |
41 | Cc: Peter Zijlstra <peterz@infradead.org> | |
42 | Cc: Will Deacon <will.deacon@arm.com> | |
43 | Cc: aliguori@amazon.com | |
44 | Cc: daniel.gruss@iaik.tugraz.at | |
45 | Cc: hughd@google.com | |
46 | Cc: keescook@google.com | |
47 | Signed-off-by: Ingo Molnar <mingo@kernel.org> | |
48 | (cherry picked from commit 03f4424f348e8be95eb1bbeba09461cd7b867828) | |
49 | Signed-off-by: Andy Whitcroft <apw@canonical.com> | |
50 | Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com> | |
51 | (cherry picked from commit 262ab7e8665e88581d20ccaefa107340457224bb) | |
52 | Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com> | |
53 | --- | |
54 | arch/x86/mm/pti.c | 127 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ | |
55 | 1 file changed, 127 insertions(+) | |
56 | ||
57 | diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c | |
58 | index 69a983365392..d58bcee470fc 100644 | |
59 | --- a/arch/x86/mm/pti.c | |
60 | +++ b/arch/x86/mm/pti.c | |
61 | @@ -48,6 +48,11 @@ | |
62 | #undef pr_fmt | |
63 | #define pr_fmt(fmt) "Kernel/User page tables isolation: " fmt | |
64 | ||
65 | +/* Backporting helper */ | |
66 | +#ifndef __GFP_NOTRACK | |
67 | +#define __GFP_NOTRACK 0 | |
68 | +#endif | |
69 | + | |
70 | static void __init pti_print_if_insecure(const char *reason) | |
71 | { | |
72 | if (boot_cpu_has_bug(X86_BUG_CPU_INSECURE)) | |
73 | @@ -137,6 +142,128 @@ pgd_t __pti_set_user_pgd(pgd_t *pgdp, pgd_t pgd) | |
74 | return pgd; | |
75 | } | |
76 | ||
77 | +/* | |
78 | + * Walk the user copy of the page tables (optionally) trying to allocate | |
79 | + * page table pages on the way down. | |
80 | + * | |
81 | + * Returns a pointer to a P4D on success, or NULL on failure. | |
82 | + */ | |
83 | +static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address) | |
84 | +{ | |
85 | + pgd_t *pgd = kernel_to_user_pgdp(pgd_offset_k(address)); | |
86 | + gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO); | |
87 | + | |
88 | + if (address < PAGE_OFFSET) { | |
89 | + WARN_ONCE(1, "attempt to walk user address\n"); | |
90 | + return NULL; | |
91 | + } | |
92 | + | |
93 | + if (pgd_none(*pgd)) { | |
94 | + unsigned long new_p4d_page = __get_free_page(gfp); | |
95 | + if (!new_p4d_page) | |
96 | + return NULL; | |
97 | + | |
98 | + if (pgd_none(*pgd)) { | |
99 | + set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page))); | |
100 | + new_p4d_page = 0; | |
101 | + } | |
102 | + if (new_p4d_page) | |
103 | + free_page(new_p4d_page); | |
104 | + } | |
105 | + BUILD_BUG_ON(pgd_large(*pgd) != 0); | |
106 | + | |
107 | + return p4d_offset(pgd, address); | |
108 | +} | |
109 | + | |
110 | +/* | |
111 | + * Walk the user copy of the page tables (optionally) trying to allocate | |
112 | + * page table pages on the way down. | |
113 | + * | |
114 | + * Returns a pointer to a PMD on success, or NULL on failure. | |
115 | + */ | |
116 | +static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address) | |
117 | +{ | |
118 | + gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO); | |
119 | + p4d_t *p4d = pti_user_pagetable_walk_p4d(address); | |
120 | + pud_t *pud; | |
121 | + | |
122 | + BUILD_BUG_ON(p4d_large(*p4d) != 0); | |
123 | + if (p4d_none(*p4d)) { | |
124 | + unsigned long new_pud_page = __get_free_page(gfp); | |
125 | + if (!new_pud_page) | |
126 | + return NULL; | |
127 | + | |
128 | + if (p4d_none(*p4d)) { | |
129 | + set_p4d(p4d, __p4d(_KERNPG_TABLE | __pa(new_pud_page))); | |
130 | + new_pud_page = 0; | |
131 | + } | |
132 | + if (new_pud_page) | |
133 | + free_page(new_pud_page); | |
134 | + } | |
135 | + | |
136 | + pud = pud_offset(p4d, address); | |
137 | + /* The user page tables do not use large mappings: */ | |
138 | + if (pud_large(*pud)) { | |
139 | + WARN_ON(1); | |
140 | + return NULL; | |
141 | + } | |
142 | + if (pud_none(*pud)) { | |
143 | + unsigned long new_pmd_page = __get_free_page(gfp); | |
144 | + if (!new_pmd_page) | |
145 | + return NULL; | |
146 | + | |
147 | + if (pud_none(*pud)) { | |
148 | + set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page))); | |
149 | + new_pmd_page = 0; | |
150 | + } | |
151 | + if (new_pmd_page) | |
152 | + free_page(new_pmd_page); | |
153 | + } | |
154 | + | |
155 | + return pmd_offset(pud, address); | |
156 | +} | |
157 | + | |
158 | +static void __init | |
159 | +pti_clone_pmds(unsigned long start, unsigned long end, pmdval_t clear) | |
160 | +{ | |
161 | + unsigned long addr; | |
162 | + | |
163 | + /* | |
164 | + * Clone the populated PMDs which cover start to end. These PMD areas | |
165 | + * can have holes. | |
166 | + */ | |
167 | + for (addr = start; addr < end; addr += PMD_SIZE) { | |
168 | + pmd_t *pmd, *target_pmd; | |
169 | + pgd_t *pgd; | |
170 | + p4d_t *p4d; | |
171 | + pud_t *pud; | |
172 | + | |
173 | + pgd = pgd_offset_k(addr); | |
174 | + if (WARN_ON(pgd_none(*pgd))) | |
175 | + return; | |
176 | + p4d = p4d_offset(pgd, addr); | |
177 | + if (WARN_ON(p4d_none(*p4d))) | |
178 | + return; | |
179 | + pud = pud_offset(p4d, addr); | |
180 | + if (pud_none(*pud)) | |
181 | + continue; | |
182 | + pmd = pmd_offset(pud, addr); | |
183 | + if (pmd_none(*pmd)) | |
184 | + continue; | |
185 | + | |
186 | + target_pmd = pti_user_pagetable_walk_pmd(addr); | |
187 | + if (WARN_ON(!target_pmd)) | |
188 | + return; | |
189 | + | |
190 | + /* | |
191 | + * Copy the PMD. That is, the kernelmode and usermode | |
192 | + * tables will share the last-level page tables of this | |
193 | + * address range | |
194 | + */ | |
195 | + *target_pmd = pmd_clear_flags(*pmd, clear); | |
196 | + } | |
197 | +} | |
198 | + | |
199 | /* | |
200 | * Initialize kernel page table isolation | |
201 | */ | |
202 | -- | |
203 | 2.14.2 | |
204 |