Commit | Line | Data |
---|---|---|
ec8f24b7 | 1 | # SPDX-License-Identifier: GPL-2.0-only |
9f671e58 KC |
2 | menu "Kernel hardening options" |
3 | ||
4 | config GCC_PLUGIN_STRUCTLEAK | |
5 | bool | |
6 | help | |
7 | While the kernel is built with warnings enabled for any missed | |
8 | stack variable initializations, this warning is silenced for | |
9 | anything passed by reference to another function, under the | |
10 | occasionally misguided assumption that the function will do | |
11 | the initialization. As this regularly leads to exploitable | |
12 | flaws, this plugin is available to identify and zero-initialize | |
13 | such variables, depending on the chosen level of coverage. | |
14 | ||
15 | This plugin was originally ported from grsecurity/PaX. More | |
16 | information at: | |
17 | * https://grsecurity.net/ | |
18 | * https://pax.grsecurity.net/ | |
19 | ||
20 | menu "Memory initialization" | |
21 | ||
709a972e KC |
22 | config CC_HAS_AUTO_VAR_INIT |
23 | def_bool $(cc-option,-ftrivial-auto-var-init=pattern) | |
24 | ||
9f671e58 KC |
25 | choice |
26 | prompt "Initialize kernel stack variables at function entry" | |
27 | default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL if COMPILE_TEST && GCC_PLUGINS | |
709a972e | 28 | default INIT_STACK_ALL if COMPILE_TEST && CC_HAS_AUTO_VAR_INIT |
9f671e58 KC |
29 | default INIT_STACK_NONE |
30 | help | |
31 | This option enables initialization of stack variables at | |
32 | function entry time. This has the possibility to have the | |
33 | greatest coverage (since all functions can have their | |
34 | variables initialized), but the performance impact depends | |
35 | on the function calling complexity of a given workload's | |
36 | syscalls. | |
37 | ||
38 | This chooses the level of coverage over classes of potentially | |
39 | uninitialized variables. The selected class will be | |
40 | initialized before use in a function. | |
41 | ||
42 | config INIT_STACK_NONE | |
43 | bool "no automatic initialization (weakest)" | |
44 | help | |
45 | Disable automatic stack variable initialization. | |
46 | This leaves the kernel vulnerable to the standard | |
47 | classes of uninitialized stack variable exploits | |
48 | and information exposures. | |
49 | ||
50 | config GCC_PLUGIN_STRUCTLEAK_USER | |
51 | bool "zero-init structs marked for userspace (weak)" | |
52 | depends on GCC_PLUGINS | |
53 | select GCC_PLUGIN_STRUCTLEAK | |
54 | help | |
55 | Zero-initialize any structures on the stack containing | |
56 | a __user attribute. This can prevent some classes of | |
57 | uninitialized stack variable exploits and information | |
58 | exposures, like CVE-2013-2141: | |
59 | https://git.kernel.org/linus/b9e146d8eb3b9eca | |
60 | ||
61 | config GCC_PLUGIN_STRUCTLEAK_BYREF | |
62 | bool "zero-init structs passed by reference (strong)" | |
63 | depends on GCC_PLUGINS | |
64 | select GCC_PLUGIN_STRUCTLEAK | |
65 | help | |
66 | Zero-initialize any structures on the stack that may | |
67 | be passed by reference and had not already been | |
68 | explicitly initialized. This can prevent most classes | |
69 | of uninitialized stack variable exploits and information | |
70 | exposures, like CVE-2017-1000410: | |
71 | https://git.kernel.org/linus/06e7e776ca4d3654 | |
72 | ||
73 | config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL | |
74 | bool "zero-init anything passed by reference (very strong)" | |
75 | depends on GCC_PLUGINS | |
76 | select GCC_PLUGIN_STRUCTLEAK | |
77 | help | |
78 | Zero-initialize any stack variables that may be passed | |
79 | by reference and had not already been explicitly | |
80 | initialized. This is intended to eliminate all classes | |
81 | of uninitialized stack variable exploits and information | |
82 | exposures. | |
83 | ||
709a972e KC |
84 | config INIT_STACK_ALL |
85 | bool "0xAA-init everything on the stack (strongest)" | |
86 | depends on CC_HAS_AUTO_VAR_INIT | |
87 | help | |
88 | Initializes everything on the stack with a 0xAA | |
89 | pattern. This is intended to eliminate all classes | |
90 | of uninitialized stack variable exploits and information | |
91 | exposures, even variables that were warned to have been | |
92 | left uninitialized. | |
93 | ||
9f671e58 KC |
94 | endchoice |
95 | ||
96 | config GCC_PLUGIN_STRUCTLEAK_VERBOSE | |
97 | bool "Report forcefully initialized variables" | |
98 | depends on GCC_PLUGIN_STRUCTLEAK | |
99 | depends on !COMPILE_TEST # too noisy | |
100 | help | |
101 | This option will cause a warning to be printed each time the | |
102 | structleak plugin finds a variable it thinks needs to be | |
103 | initialized. Since not all existing initializers are detected | |
104 | by the plugin, this can produce false positive warnings. | |
105 | ||
b6a6a377 KC |
106 | config GCC_PLUGIN_STACKLEAK |
107 | bool "Poison kernel stack before returning from syscalls" | |
108 | depends on GCC_PLUGINS | |
109 | depends on HAVE_ARCH_STACKLEAK | |
110 | help | |
111 | This option makes the kernel erase the kernel stack before | |
112 | returning from system calls. This has the effect of leaving | |
113 | the stack initialized to the poison value, which both reduces | |
114 | the lifetime of any sensitive stack contents and reduces | |
115 | potential for uninitialized stack variable exploits or information | |
116 | exposures (it does not cover functions reaching the same stack | |
117 | depth as prior functions during the same syscall). This blocks | |
118 | most uninitialized stack variable attacks, with the performance | |
119 | impact being driven by the depth of the stack usage, rather than | |
120 | the function calling complexity. | |
121 | ||
122 | The performance impact on a single CPU system kernel compilation | |
123 | sees a 1% slowdown, other systems and workloads may vary and you | |
124 | are advised to test this feature on your expected workload before | |
125 | deploying it. | |
126 | ||
127 | This plugin was ported from grsecurity/PaX. More information at: | |
128 | * https://grsecurity.net/ | |
129 | * https://pax.grsecurity.net/ | |
130 | ||
131 | config STACKLEAK_TRACK_MIN_SIZE | |
132 | int "Minimum stack frame size of functions tracked by STACKLEAK" | |
133 | default 100 | |
134 | range 0 4096 | |
135 | depends on GCC_PLUGIN_STACKLEAK | |
136 | help | |
137 | The STACKLEAK gcc plugin instruments the kernel code for tracking | |
138 | the lowest border of the kernel stack (and for some other purposes). | |
139 | It inserts the stackleak_track_stack() call for the functions with | |
140 | a stack frame size greater than or equal to this parameter. | |
141 | If unsure, leave the default value 100. | |
142 | ||
143 | config STACKLEAK_METRICS | |
144 | bool "Show STACKLEAK metrics in the /proc file system" | |
145 | depends on GCC_PLUGIN_STACKLEAK | |
146 | depends on PROC_FS | |
147 | help | |
148 | If this is set, STACKLEAK metrics for every task are available in | |
149 | the /proc file system. In particular, /proc/<pid>/stack_depth | |
150 | shows the maximum kernel stack consumption for the current and | |
151 | previous syscalls. Although this information is not precise, it | |
152 | can be useful for estimating the STACKLEAK performance impact for | |
153 | your workloads. | |
154 | ||
155 | config STACKLEAK_RUNTIME_DISABLE | |
156 | bool "Allow runtime disabling of kernel stack erasing" | |
157 | depends on GCC_PLUGIN_STACKLEAK | |
158 | help | |
159 | This option provides 'stack_erasing' sysctl, which can be used in | |
160 | runtime to control kernel stack erasing for kernels built with | |
161 | CONFIG_GCC_PLUGIN_STACKLEAK. | |
162 | ||
9f671e58 KC |
163 | endmenu |
164 | ||
165 | endmenu |