| Message ID | 1433539683-29539-1-git-send-email-jistone@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Josh, Thanks for the patch. On Fri, Jun 05, 2015 at 10:28:03PM +0100, Josh Stone wrote: > 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. > > v2: Re-enable interrupts before branching to __sys_trace_return. Please don't include the changelog in the commit message. > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Russell King <rmk+kernel@arm.linux.org.uk> > Signed-off-by: Josh Stone <jistone@redhat.com> > --- > 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 959fe8733560..988bea43dc74 100644 > --- a/arch/arm64/kernel/entry.S > +++ b/arch/arm64/kernel/entry.S > @@ -608,11 +608,16 @@ 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 Looks good to me: Reviewed-by: Will Deacon <will.deacon@arm.com> I assume this can wait until 4.2? Will
On 06/08/2015 03:21 AM, Will Deacon wrote: >> v2: Re-enable interrupts before branching to __sys_trace_return. > > Please don't include the changelog in the commit message. Ok - do you need me to resend without it? > I assume this can wait until 4.2? That's fine with me, thanks.
On Mon, Jun 08, 2015 at 09:37:32AM -0700, Josh Stone wrote: > On 06/08/2015 03:21 AM, Will Deacon wrote: > >> v2: Re-enable interrupts before branching to __sys_trace_return. > > > > Please don't include the changelog in the commit message. > > Ok - do you need me to resend without it? No need to. I'll edit the line out and queue the patch for 4.2. Thanks.
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 959fe8733560..988bea43dc74 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -608,11 +608,16 @@ 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.
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. v2: Re-enable interrupts before branching to __sys_trace_return. Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Josh Stone <jistone@redhat.com> --- arch/arm64/kernel/entry.S | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)