path: root/arch/arm/include
diff options
authorRussell King <rmk+kernel@arm.linux.org.uk>2015-09-21 19:34:28 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2015-10-03 16:36:45 +0100
commitdb695c0509d6ec9046ee5e4c520a19fa17d9fce2 (patch)
tree450931f1b93e62351049933a916ed5ac1037d236 /arch/arm/include
parent6f56a68d0bed16c13e9ec958cd28acbc2991d495 (diff)
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/include')
1 files changed, 0 insertions, 7 deletions
diff --git a/arch/arm/include/asm/unistd.h b/arch/arm/include/asm/unistd.h
index 32640c431a08..8f63daf3efa3 100644
--- a/arch/arm/include/asm/unistd.h
+++ b/arch/arm/include/asm/unistd.h
@@ -21,13 +21,6 @@
#define __NR_syscalls (388)
- * *NOTE*: This is a ghost syscall private to the kernel. Only the
- * __kuser_cmpxchg code in entry-armv.S should be aware of its
- * existence. Don't ever use this from user code.
- */
-#define __ARM_NR_cmpxchg (__ARM_NR_BASE+0x00fff0)
#define __ARCH_WANT_STAT64