commit 04d7e098f541769721d7511d56aea4b976fd29fd upstream. If a syscall is entered without TIF_SYSCALL_TRACE set, then it goes on the fast path. It's then possible to have TIF_SYSCALL_TRACE added in the middle of the syscall, but ret_fast_syscall doesn't check this flag again. This causes a ptrace syscall-exit-stop to be missed. For instance, from a PTRACE_EVENT_FORK reported during do_fork, the tracer might resume with PTRACE_SYSCALL, setting TIF_SYSCALL_TRACE. Now the completion of the fork should have a syscall-exit-stop. Russell King fixed this on arm by re-checking _TIF_SYSCALL_WORK in the fast exit path. Do the same on arm64. Reviewed-by: Will Deacon <will.deacon@xxxxxxx> Cc: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx> Signed-off-by: Josh Stone <jistone@xxxxxxxxxx> Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> Signed-off-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx> --- arch/arm64/kernel/entry.S | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index bddd04d..6657a09 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -609,11 +609,16 @@ ENDPROC(cpu_switch_to) */ ret_fast_syscall: disable_irq // disable interrupts - ldr x1, [tsk, #TI_FLAGS] + ldr x1, [tsk, #TI_FLAGS] // re-check for syscall tracing + and x2, x1, #_TIF_SYSCALL_WORK + cbnz x2, ret_fast_syscall_trace and x2, x1, #_TIF_WORK_MASK cbnz x2, fast_work_pending enable_step_tsk x1, x2 kernel_exit 0, ret = 1 +ret_fast_syscall_trace: + enable_irq // enable interrupts + b __sys_trace_return /* * Ok, we need to do extra processing, enter the slow path. -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html