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| author | Russell King <rmk+kernel@arm.linux.org.uk> | 2015-09-21 21:34:28 +0300 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2015-10-03 18:36:45 +0300 |
| commit | db695c0509d6ec9046ee5e4c520a19fa17d9fce2 (patch) | |
| tree | 450931f1b93e62351049933a916ed5ac1037d236 /arch/arm/mm | |
| parent | 6f56a68d0bed16c13e9ec958cd28acbc2991d495 (diff) | |
| download | linux-db695c0509d6ec9046ee5e4c520a19fa17d9fce2.tar.xz | |
ARM: remove user cmpxchg syscall
Mark Brand reports that a NEEDS_SYSCALL_FOR_CMPXCHG enabled kernel would
open a security hole in the ghost syscall used to implement cmpxchg, as
it fails to validate the user pointer.
However, in order for this option to be enabled, you'd need to be
building a pre-ARMv6 kernel with SMP support. There is only one system
known which fits that, which is an early ARM SMP FPGA implementation
based on the ARM926T.
In any case, the Kconfig does not allow SMP to be enabled for pre-ARMv6
systems.
Moreover, even if NEEDS_SYSCALL_FOR_CMPXCHG were to be enabled, the
kernel would not build as __ARM_NR_cmpxchg64 is not defined.
The simple answer is to remove the buggy code.
Reported-by: Mark Brand <markbrand@google.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/mm')
| -rw-r--r-- | arch/arm/mm/Kconfig | 12 |
1 files changed, 0 insertions, 12 deletions
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig index df7537f12469..c21941349b3e 100644 --- a/arch/arm/mm/Kconfig +++ b/arch/arm/mm/Kconfig @@ -419,28 +419,24 @@ config CPU_THUMBONLY config CPU_32v3 bool select CPU_USE_DOMAINS if MMU - select NEEDS_SYSCALL_FOR_CMPXCHG if SMP select NEED_KUSER_HELPERS select TLS_REG_EMUL if SMP || !MMU config CPU_32v4 bool select CPU_USE_DOMAINS if MMU - select NEEDS_SYSCALL_FOR_CMPXCHG if SMP select NEED_KUSER_HELPERS select TLS_REG_EMUL if SMP || !MMU config CPU_32v4T bool select CPU_USE_DOMAINS if MMU - select NEEDS_SYSCALL_FOR_CMPXCHG if SMP select NEED_KUSER_HELPERS select TLS_REG_EMUL if SMP || !MMU config CPU_32v5 bool select CPU_USE_DOMAINS if MMU - select NEEDS_SYSCALL_FOR_CMPXCHG if SMP select NEED_KUSER_HELPERS select TLS_REG_EMUL if SMP || !MMU @@ -805,14 +801,6 @@ config TLS_REG_EMUL a few prototypes like that in existence) and therefore access to that required register must be emulated. -config NEEDS_SYSCALL_FOR_CMPXCHG - bool - select NEED_KUSER_HELPERS - help - SMP on a pre-ARMv6 processor? Well OK then. - Forget about fast user space cmpxchg support. - It is just not possible. - config NEED_KUSER_HELPERS bool |