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Diffstat (limited to 'arch/x86/Kconfig')
| -rw-r--r-- | arch/x86/Kconfig | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 255ea22ccbec..db3622f22b61 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2027,6 +2027,55 @@ config COMPAT_VDSO If unsure, say N: if you are compiling your own kernel, you are unlikely to be using a buggy version of glibc. +choice + prompt "vsyscall table for legacy applications" + depends on X86_64 + default LEGACY_VSYSCALL_EMULATE + help + Legacy user code that does not know how to find the vDSO expects + to be able to issue three syscalls by calling fixed addresses in + kernel space. Since this location is not randomized with ASLR, + it can be used to assist security vulnerability exploitation. + + This setting can be changed at boot time via the kernel command + line parameter vsyscall=[native|emulate|none]. + + On a system with recent enough glibc (2.14 or newer) and no + static binaries, you can say None without a performance penalty + to improve security. + + If unsure, select "Emulate". + + config LEGACY_VSYSCALL_NATIVE + bool "Native" + help + Actual executable code is located in the fixed vsyscall + address mapping, implementing time() efficiently. Since + this makes the mapping executable, it can be used during + security vulnerability exploitation (traditionally as + ROP gadgets). This configuration is not recommended. + + config LEGACY_VSYSCALL_EMULATE + bool "Emulate" + help + The kernel traps and emulates calls into the fixed + vsyscall address mapping. This makes the mapping + non-executable, but it still contains known contents, + which could be used in certain rare security vulnerability + exploits. This configuration is recommended when userspace + still uses the vsyscall area. + + config LEGACY_VSYSCALL_NONE + bool "None" + help + There will be no vsyscall mapping at all. This will + eliminate any risk of ASLR bypass due to the vsyscall + fixed address mapping. Attempts to use the vsyscalls + will be reported to dmesg, so that either old or + malicious userspace programs can be identified. + +endchoice + config CMDLINE_BOOL bool "Built-in kernel command line" ---help--- |