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Kernel: Audit Support For The ARM Platform

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This patch provides functionality to audit system call events on the
ARM platform. The implementation was based off the structure of the
MIPS platform and information in this
(http://lists.fedoraproject.org/pipermail/arm/2009-October/000382.html)
mailing list thread. The required audit_syscall_exit and
audit_syscall_entry checks were added to ptrace using the standard
registers for system call values (r0 through r3). A thread information
flag was added for auditing (TIF_SYSCALL_AUDIT) and a meta-flag was
added (_TIF_SYSCALL_WORK) to simplify modifications to the syscall
entry/exit. Now, if either the TRACE flag is set or the AUDIT flag is
set, the syscall_trace function will be executed. The prober changes
were made to Kconfig to allow CONFIG_AUDITSYSCALL to be enabled.

Due to platform availability limitations, this patch was only tested
on the Android platform running the modified "android-goldfish-2.6.29"
kernel. A test compile was performed using Code Sourcery's
cross-compilation toolset and the current linux-3.0 stable kernel. The
changes compile without error. I'm hoping, due to the simple modifications,
the patch is "obviously correct".

Signed-off-by: Nathaniel Husted <nhusted@gmail.com>
Signed-off-by: Eric Paris <eparis@redhat.com>
This commit is contained in:
Nathaniel Husted 2012-01-03 14:23:09 -05:00 committed by Al Viro
parent 4043cde8ec
commit 29ef73b7a8
6 changed files with 25 additions and 9 deletions
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1
arch/arm/include/asm/kprobes.h
View File

@ -24,7 +24,6 @@
#define MAX_INSN_SIZE 2
#define MAX_STACK_SIZE 64 /* 32 would probably be OK */
#define regs_return_value(regs) ((regs)->ARM_r0)
#define flush_insn_slot(p) do { } while (0)
#define kretprobe_blacklist_size 0

5
arch/arm/include/asm/ptrace.h
View File

@ -189,6 +189,11 @@ static inline int valid_user_regs(struct pt_regs *regs)
return 0;
}
static inline long regs_return_value(struct pt_regs *regs)
{
return regs->ARM_r0;
}
#define instruction_pointer(regs) (regs)->ARM_pc
#ifdef CONFIG_SMP

6
arch/arm/include/asm/thread_info.h
View File

@ -129,6 +129,7 @@ extern void vfp_flush_hwstate(struct thread_info *);
/*
* thread information flags:
* TIF_SYSCALL_TRACE - syscall trace active
* TIF_SYSCAL_AUDIT - syscall auditing active
* TIF_SIGPENDING - signal pending
* TIF_NEED_RESCHED - rescheduling necessary
* TIF_NOTIFY_RESUME - callback before returning to user
@ -139,6 +140,7 @@ extern void vfp_flush_hwstate(struct thread_info *);
#define TIF_NEED_RESCHED 1
#define TIF_NOTIFY_RESUME 2 /* callback before returning to user */
#define TIF_SYSCALL_TRACE 8
#define TIF_SYSCALL_AUDIT 9
#define TIF_POLLING_NRFLAG 16
#define TIF_USING_IWMMXT 17
#define TIF_MEMDIE 18 /* is terminating due to OOM killer */
@ -149,11 +151,15 @@ extern void vfp_flush_hwstate(struct thread_info *);
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
#define _TIF_USING_IWMMXT (1 << TIF_USING_IWMMXT)
#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)
#define _TIF_SECCOMP (1 << TIF_SECCOMP)
/* Checks for any syscall work in entry-common.S */
#define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT)
/*
* Change these and you break ASM code in entry-common.S
*/

4
arch/arm/kernel/entry-common.S
View File

@ -87,7 +87,7 @@ ENTRY(ret_from_fork)
get_thread_info tsk
ldr r1, [tsk, #TI_FLAGS] @ check for syscall tracing
mov why, #1
tst r1, #_TIF_SYSCALL_TRACE @ are we tracing syscalls?
tst r1, #_TIF_SYSCALL_WORK @ are we tracing syscalls?
beq ret_slow_syscall
mov r1, sp
mov r0, #1 @ trace exit [IP = 1]
@ -443,7 +443,7 @@ ENTRY(vector_swi)
1:
#endif
tst r10, #_TIF_SYSCALL_TRACE @ are we tracing syscalls?
tst r10, #_TIF_SYSCALL_WORK @ are we tracing syscalls?
bne __sys_trace
cmp scno, #NR_syscalls @ check upper syscall limit

16
arch/arm/kernel/ptrace.c
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@ -906,11 +906,6 @@ asmlinkage int syscall_trace(int why, struct pt_regs *regs, int scno)
{
unsigned long ip;
if (!test_thread_flag(TIF_SYSCALL_TRACE))
return scno;
if (!(current->ptrace & PT_PTRACED))
return scno;
/*
* Save IP. IP is used to denote syscall entry/exit:
* IP = 0 -> entry, = 1 -> exit
@ -918,6 +913,17 @@ asmlinkage int syscall_trace(int why, struct pt_regs *regs, int scno)
ip = regs->ARM_ip;
regs->ARM_ip = why;
if (!ip)
audit_syscall_exit(regs);
else
audit_syscall_entry(AUDIT_ARCH_ARMEB, scno, regs->ARM_r0,
regs->ARM_r1, regs->ARM_r2, regs->ARM_r3);
if (!test_thread_flag(TIF_SYSCALL_TRACE))
return scno;
if (!(current->ptrace & PT_PTRACED))
return scno;
current_thread_info()->syscall = scno;
/* the 0x80 provides a way for the tracing parent to distinguish

2
init/Kconfig
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@ -355,7 +355,7 @@ config AUDIT
config AUDITSYSCALL
bool "Enable system-call auditing support"
depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || ARM)
default y if SECURITY_SELINUX
help
Enable low-overhead system-call auditing infrastructure that