From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com> To: Mark Brown <broonie@kernel.org> Cc: jpoimboe@redhat.com, mark.rutland@arm.com, jthierry@redhat.com, catalin.marinas@arm.com, will@kernel.org, jmorris@namei.org, pasha.tatashin@soleen.com, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v3 2/4] arm64: Check the return PC against unreliable code sections Date: Wed, 5 May 2021 13:50:23 -0500 [thread overview] Message-ID: <8ea6a81a-2e19-f752-408c-21dea1078f9b@linux.microsoft.com> (raw) In-Reply-To: <9781011e-2d99-7f46-592c-621c66ea66c3@linux.microsoft.com> On 5/5/21 1:48 PM, Madhavan T. Venkataraman wrote: > > > On 5/5/21 11:46 AM, Mark Brown wrote: >> On Tue, May 04, 2021 at 02:32:35PM -0500, Madhavan T. Venkataraman wrote: >> >>> If you prefer, I could do something like this: >>> >>> check_pc: >>> if (!__kernel_text_address(frame->pc)) >>> frame->reliable = false; >>> >>> range = lookup_range(frame->pc); >>> >>> #ifdef CONFIG_FUNCTION_GRAPH_TRACER >>> if (tsk->ret_stack && >>> frame->pc == (unsigned long)return_to_handler) { >>> ... >>> frame->pc = ret_stack->ret; >>> frame->pc = ptrauth_strip_insn_pac(frame->pc); >>> goto check_pc; >>> } >>> #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ >> >>> Is that acceptable? >> >> I think that works even if it's hard to love the goto, might want some >> defensiveness to ensure we can't somehow end up in an infinite loop with >> a sufficiently badly formed stack. >> > > I could do something like this: > > - Move all frame->pc checking code into a function called check_frame_pc(). > > bool check_frame_pc(frame) > { > Do all the checks including function graph > return frame->pc changed > } > > - Then, in unwind_frame() > > unwind_frame() > { > int i; > ... > > for (i = 0; i < MAX_CHECKS; i++) { > if (!check_frame(tsk, frame)) Small typo in the last statement - It should be check_frame_pc(). Sorry. Madhavan > break; > } > > if (i == MAX_CHECKS) > frame->reliable = false; > return 0; > } > > The above would take care of future cases like kretprobe_trampoline(). > > If this is acceptable, then the only question is - what should be the value of > MAX_CHECKS (I will rename it to something more appropriate)? > > Madhavan >
WARNING: multiple messages have this Message-ID (diff)
From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com> To: Mark Brown <broonie@kernel.org> Cc: jpoimboe@redhat.com, mark.rutland@arm.com, jthierry@redhat.com, catalin.marinas@arm.com, will@kernel.org, jmorris@namei.org, pasha.tatashin@soleen.com, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v3 2/4] arm64: Check the return PC against unreliable code sections Date: Wed, 5 May 2021 13:50:23 -0500 [thread overview] Message-ID: <8ea6a81a-2e19-f752-408c-21dea1078f9b@linux.microsoft.com> (raw) In-Reply-To: <9781011e-2d99-7f46-592c-621c66ea66c3@linux.microsoft.com> On 5/5/21 1:48 PM, Madhavan T. Venkataraman wrote: > > > On 5/5/21 11:46 AM, Mark Brown wrote: >> On Tue, May 04, 2021 at 02:32:35PM -0500, Madhavan T. Venkataraman wrote: >> >>> If you prefer, I could do something like this: >>> >>> check_pc: >>> if (!__kernel_text_address(frame->pc)) >>> frame->reliable = false; >>> >>> range = lookup_range(frame->pc); >>> >>> #ifdef CONFIG_FUNCTION_GRAPH_TRACER >>> if (tsk->ret_stack && >>> frame->pc == (unsigned long)return_to_handler) { >>> ... >>> frame->pc = ret_stack->ret; >>> frame->pc = ptrauth_strip_insn_pac(frame->pc); >>> goto check_pc; >>> } >>> #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ >> >>> Is that acceptable? >> >> I think that works even if it's hard to love the goto, might want some >> defensiveness to ensure we can't somehow end up in an infinite loop with >> a sufficiently badly formed stack. >> > > I could do something like this: > > - Move all frame->pc checking code into a function called check_frame_pc(). > > bool check_frame_pc(frame) > { > Do all the checks including function graph > return frame->pc changed > } > > - Then, in unwind_frame() > > unwind_frame() > { > int i; > ... > > for (i = 0; i < MAX_CHECKS; i++) { > if (!check_frame(tsk, frame)) Small typo in the last statement - It should be check_frame_pc(). Sorry. Madhavan > break; > } > > if (i == MAX_CHECKS) > frame->reliable = false; > return 0; > } > > The above would take care of future cases like kretprobe_trampoline(). > > If this is acceptable, then the only question is - what should be the value of > MAX_CHECKS (I will rename it to something more appropriate)? > > Madhavan > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-05-05 18:50 UTC|newest] Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <65cf4dfbc439b010b50a0c46ec500432acde86d6> 2021-05-03 17:36 ` [RFC PATCH v3 0/4] arm64: Stack trace reliability checks in the unwinder madvenka 2021-05-03 17:36 ` madvenka 2021-05-03 17:36 ` [RFC PATCH v3 1/4] arm64: Introduce stack " madvenka 2021-05-03 17:36 ` madvenka 2021-05-04 15:50 ` Mark Brown 2021-05-04 15:50 ` Mark Brown 2021-05-04 19:14 ` Madhavan T. Venkataraman 2021-05-04 19:14 ` Madhavan T. Venkataraman 2021-05-04 21:52 ` Josh Poimboeuf 2021-05-04 21:52 ` Josh Poimboeuf 2021-05-04 23:13 ` Madhavan T. Venkataraman 2021-05-04 23:13 ` Madhavan T. Venkataraman 2021-05-05 0:07 ` Josh Poimboeuf 2021-05-05 0:07 ` Josh Poimboeuf 2021-05-05 0:21 ` Madhavan T. Venkataraman 2021-05-05 0:21 ` Madhavan T. Venkataraman 2021-05-03 17:36 ` [RFC PATCH v3 2/4] arm64: Check the return PC against unreliable code sections madvenka 2021-05-03 17:36 ` madvenka 2021-05-04 16:05 ` Mark Brown 2021-05-04 16:05 ` Mark Brown 2021-05-04 19:03 ` Madhavan T. Venkataraman 2021-05-04 19:03 ` Madhavan T. Venkataraman 2021-05-04 19:32 ` Madhavan T. Venkataraman 2021-05-04 19:32 ` Madhavan T. Venkataraman 2021-05-05 16:46 ` Mark Brown 2021-05-05 16:46 ` Mark Brown 2021-05-05 18:48 ` Madhavan T. Venkataraman 2021-05-05 18:48 ` Madhavan T. Venkataraman 2021-05-05 18:50 ` Madhavan T. Venkataraman [this message] 2021-05-05 18:50 ` Madhavan T. Venkataraman 2021-05-06 13:45 ` Mark Brown 2021-05-06 13:45 ` Mark Brown 2021-05-06 15:21 ` Madhavan T. Venkataraman 2021-05-06 15:21 ` Madhavan T. Venkataraman 2021-05-05 16:34 ` Mark Brown 2021-05-05 16:34 ` Mark Brown 2021-05-05 17:51 ` Madhavan T. Venkataraman 2021-05-05 17:51 ` Madhavan T. Venkataraman 2021-05-05 19:30 ` Ard Biesheuvel 2021-05-05 19:30 ` Ard Biesheuvel 2021-05-05 20:00 ` Madhavan T. Venkataraman 2021-05-05 20:00 ` Madhavan T. Venkataraman 2021-05-03 17:36 ` [RFC PATCH v3 3/4] arm64: Handle miscellaneous functions in .text and .init.text madvenka 2021-05-03 17:36 ` madvenka 2021-05-06 14:12 ` Mark Brown 2021-05-06 14:12 ` Mark Brown 2021-05-06 15:30 ` Madhavan T. Venkataraman 2021-05-06 15:30 ` Madhavan T. Venkataraman 2021-05-06 15:32 ` Madhavan T. Venkataraman 2021-05-06 15:32 ` Madhavan T. Venkataraman 2021-05-06 15:44 ` Mark Brown 2021-05-06 15:44 ` Mark Brown 2021-05-06 15:56 ` Madhavan T. Venkataraman 2021-05-06 15:56 ` Madhavan T. Venkataraman 2021-05-06 15:37 ` Mark Brown 2021-05-06 15:37 ` Mark Brown 2021-05-06 15:57 ` Madhavan T. Venkataraman 2021-05-06 15:57 ` Madhavan T. Venkataraman 2021-05-03 17:36 ` [RFC PATCH v3 4/4] arm64: Handle funtion graph tracer better in the unwinder madvenka 2021-05-03 17:36 ` madvenka 2021-05-06 14:43 ` Mark Brown 2021-05-06 14:43 ` Mark Brown 2021-05-06 15:20 ` Madhavan T. Venkataraman 2021-05-06 15:20 ` Madhavan T. Venkataraman
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