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| author | Vincenzo Frascino <vincenzo.frascino@arm.com> | 2019-04-15 11:49:37 +0200 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2019-04-23 19:01:58 +0200 |
| commit | af1b3cf2c2a3f42bbb680812ff1bbd715ac8af69 (patch) | |
| tree | 67550d4018c6cc1e368214556d744317da53e689 /arch/arm64/Kconfig | |
| parent | arm64: compat: Refactor aarch32_alloc_vdso_pages() (diff) | |
| download | linux-af1b3cf2c2a3f42bbb680812ff1bbd715ac8af69.tar.xz linux-af1b3cf2c2a3f42bbb680812ff1bbd715ac8af69.zip | |
arm64: compat: Add KUSER_HELPERS config option
When kuser helpers are enabled the kernel maps the relative code at
a fixed address (0xffff0000). Making configurable the option to disable
them means that the kernel can remove this mapping and any access to
this memory area results in a sigfault.
Add a KUSER_HELPERS config option that can be used to disable the
mapping when it is turned off.
This option can be turned off if and only if the applications are
designed specifically for the platform and they do not make use of the
kuser helpers code.
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
[will: Use IS_ENABLED() instead of #ifdef]
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/Kconfig')
| -rw-r--r-- | arch/arm64/Kconfig | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index c383625ec02c..0861a6f5ee4a 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1498,6 +1498,34 @@ config COMPAT If you want to execute 32-bit userspace applications, say Y. +config KUSER_HELPERS + bool "Enable kuser helpers page for 32 bit applications." + depends on COMPAT + default y + help + Warning: disabling this option may break 32-bit user programs. + + Provide kuser helpers to compat tasks. The kernel provides + helper code to userspace in read only form at a fixed location + to allow userspace to be independent of the CPU type fitted to + the system. This permits binaries to be run on ARMv4 through + to ARMv8 without modification. + + See Documentation/arm/kernel_user_helpers.txt for details. + + However, the fixed address nature of these helpers can be used + by ROP (return orientated programming) authors when creating + exploits. + + If all of the binaries and libraries which run on your platform + are built specifically for your platform, and make no use of + these helpers, then you can turn this option off to hinder + such exploits. However, in that case, if a binary or library + relying on those helpers is run, it will not function correctly. + + Say N here only if you are absolutely certain that you do not + need these helpers; otherwise, the safe option is to say Y. + config SYSVIPC_COMPAT def_bool y depends on COMPAT && SYSVIPC |