Hi Akashi,
On Tue, Sep 09, 2014 at 05:49:59AM +0100, AKASHI Takahiro wrote:
> BUG_ON() in audit_syscall_entry() will be hit if user issues syscall(-1)
> while syscall auditing is enabled (that is, by starting auditd).
[...]
> diff --git a/arch/arm/include/asm/traps.h b/arch/arm/include/asm/traps.h
> index f555bb3..de01145 100644
> --- a/arch/arm/include/asm/traps.h
> +++ b/arch/arm/include/asm/traps.h
> @@ -49,6 +49,7 @@ static inline int in_exception_text(unsigned long ptr)
> extern void __init early_trap_init(void *);
> extern void dump_backtrace_entry(unsigned long where, unsigned long from,
> unsigned long frame);
> extern void ptrace_break(struct task_struct *tsk, struct pt_regs *regs);
> +extern int arm_syscall(int no, struct pt_regs *regs);
>
> extern void *vectors_page;
>
> diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
> index e52fe5a..28d3931 100644
> --- a/arch/arm/kernel/entry-common.S
> +++ b/arch/arm/kernel/entry-common.S
> @@ -426,7 +426,6 @@ ENTRY(vector_swi)
> local_restart:
> ldr r10, [tsk, #TI_FLAGS] @ check for syscall tracing
> stmdb sp!, {r4, r5} @ push fifth and sixth args
> -
You don't need this cosmetic change.
> tst r10, #_TIF_SYSCALL_WORK @ are we tracing syscalls?
> bne __sys_trace
>
> @@ -476,10 +475,11 @@ __sys_trace:
> cmp scno, #-1 @ skip the syscall?
> bne 2b
> add sp, sp, #S_OFF @ restore stack
> - b ret_slow_syscall
> + b __sys_trace_return_skipped
Can't you just remove the add as well, them fall-through here?
>
> __sys_trace_return:
> str r0, [sp, #S_R0 + S_OFF]! @ save returned r0
> +__sys_trace_return_skipped:
> mov r0, sp
> bl syscall_trace_exit
> b ret_slow_syscall
> diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
> index 0c27ed6..68b42cd 100644
> --- a/arch/arm/kernel/ptrace.c
> +++ b/arch/arm/kernel/ptrace.c
> @@ -930,7 +930,9 @@ static void tracehook_report_syscall(struct pt_regs *regs,
>
> asmlinkage int syscall_trace_enter(struct pt_regs *regs, int scno)
> {
> - current_thread_info()->syscall = scno;
> + int orig_scno;
> +
> + current_thread_info()->syscall = orig_scno = scno;
>
> /* Do the secure computing check first; failures should be fast. */
> if (secure_computing(scno) == -1)
> @@ -941,31 +943,40 @@ asmlinkage int syscall_trace_enter(struct pt_regs
> *regs, int scno)
>
> scno = current_thread_info()->syscall;
>
> - if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
> - trace_sys_enter(regs, scno);
> + if (scno >= 0 && scno < NR_syscalls) {
Is this supposed to work for OABI? If so, better use __NR_SYSCALL_BASE.
> + if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
> + trace_sys_enter(regs, scno);
> +
> + audit_syscall_entry(AUDIT_ARCH_ARM, scno,
> + regs->ARM_r0, regs->ARM_r1,
> + regs->ARM_r2, regs->ARM_r3);
> + }
>
> - audit_syscall_entry(AUDIT_ARCH_ARM, scno, regs->ARM_r0, regs->ARM_r1,
> - regs->ARM_r2, regs->ARM_r3);
> + /* user-issued syscall of -1 */
> + if (scno == -1 && orig_scno == -1)
Make this an else if, for clarity?
> + arm_syscall(scno, regs);
Doesn't this always result in bad_syscall being called, which sends a SIGILL
to the task? Shouldn't we simply return -ENOSYS instead? You could do that
in the assembly code.
> return scno;
> }
>
> asmlinkage void syscall_trace_exit(struct pt_regs *regs)
> {
> - /*
> - * Audit the syscall before anything else, as a debugger may
> - * come in and change the current registers.
> - */
> - audit_syscall_exit(regs);
> + if (current_thread_info()->syscall < NR_syscalls) {
Again, not going to work for OABI.
Will
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
