From: Pratyush Anand <panand@redhat.com> To: James Morse <james.morse@arm.com> Cc: "David Long" <dave.long@linaro.org>, "Catalin Marinas" <catalin.marinas@arm.com>, "Will Deacon" <will.deacon@arm.com>, "Sandeepa Prabhu" <sandeepa.s.prabhu@gmail.com>, "William Cohen" <wcohen@redhat.com>, "Steve Capper" <steve.capper@linaro.org>, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, "Marc Zyngier" <marc.zyngier@arm.com>, "Dave P Martin" <Dave.Martin@arm.com>, "Mark Rutland" <mark.rutland@arm.com>, "Robin Murphy" <Robin.Murphy@arm.com>, "Ard Biesheuvel" <ard.biesheuvel@linaro.org>, "Jens Wiklander" <jens.wiklander@linaro.org>, "Christoffer Dall" <christoffer.dall@linaro.org>, "Alex Bennée" <alex.bennee@linaro.org>, "Yang Shi" <yang.shi@linaro.org>, "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>, "Viresh Kumar" <viresh.kumar@linaro.org>, "Suzuki K. Poulose" <suzuki.poulose@arm.com>, "Kees Cook" <keescook@chromium.org>, "Zi Shen Lim" <zlim.lnx@gmail.com>, "John Blackwood" <john.blackwood@ccur.com>, "Feng Kan" <fkan@apm.com>, "Balamurugan Shanmugam" <bshanmugam@apm.com>, "Vladimir Murzin" <Vladimir.Murzin@arm.com>, "Mark Salyzyn" <salyzyn@android.com>, "Petr Mladek" <pmladek@suse.com>, "Andrew Morton" <akpm@linux-foundation.org>, "Mark Brown" <broonie@kernel.org> Subject: Re: [PATCH v11 3/9] arm64: add copy_to/from_user to kprobes blacklist Date: Wed, 16 Mar 2016 11:13:56 +0530 [thread overview] Message-ID: <20160316054329.GC28915@dhcppc6.redhat.com> (raw) In-Reply-To: <56E858D8.8030300@arm.com> On 15/03/2016:06:47:52 PM, James Morse wrote: > Hi David, > > On 09/03/16 05:32, David Long wrote: > > From: "David A. Long" <dave.long@linaro.org> > > diff --git a/arch/arm64/lib/copy_from_user.S b/arch/arm64/lib/copy_from_user.S > > index 4699cd7..0ac2131 100644 > > --- a/arch/arm64/lib/copy_from_user.S > > +++ b/arch/arm64/lib/copy_from_user.S > > @@ -66,6 +66,7 @@ > > .endm > > > > end .req x5 > > + .section .kprobes.text,"ax",%progbits > > ENTRY(__copy_from_user) > > ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(0)), ARM64_HAS_PAN, \ > > CONFIG_ARM64_PAN) > > diff --git a/arch/arm64/lib/copy_to_user.S b/arch/arm64/lib/copy_to_user.S > > index 7512bbb..e4eb84c 100644 > > --- a/arch/arm64/lib/copy_to_user.S > > +++ b/arch/arm64/lib/copy_to_user.S > > @@ -65,6 +65,7 @@ > > .endm > > > > end .req x5 > > + .section .kprobes.text,"ax",%progbits > > ENTRY(__copy_to_user) > > ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(0)), ARM64_HAS_PAN, \ > > CONFIG_ARM64_PAN) > > > > If I understand this correctly - you can't kprobe these ldr/str instructions as > the fault handler wouldn't find kprobe's out-of line version of the instruction > in the exception table... but why only these two functions? (for library > functions, we also have clear_user() and copy_in_user()...) May be not clear_user() because those are inlined, but may be __clear_user(). There can be many other functions (see [1], [2] and can be many more) which need to be blacklisted, but I think they can always be added latter on, and atleast this aspect should not hinder inclusion of these patches. > > The get_user()/put_user() stuff in uaccess.h gets inlined all over the kernel, I > don't think its feasible to put all of these in a separate section. Yes, It does not seem possible to blacklist inlined functions. There can be some other places like valid kprobable instructions in atomic context, .word instruction having data as valid instruction, etc... So, probably its not possible to make 100% safe, but yes wherever possible, we should take care. Infact, other ARCHs are also not completely safe. One can try to instrument kprobe on all the symbols in Kallsyms on an x86_64 machine and kernel crashes. > > Is it feasible to search the exception table at runtime instead? If an > address-to-be-kprobed appears in the list, we know it could generate exceptions, > so we should report that we can't probe this address. That would catch all of > the library functions, all the places uaccess.h was inlined, and anything new > that gets invented in the future. Sorry, probably I could not get it. How can an inlined addresses range be placed in exception table or any other code area. ~Pratyush [1] https://github.com/pratyushanand/linux/commit/855bc4dbb98ceafac4c933e00d203b1cd7ee9ca4 [2] https://github.com/pratyushanand/linux/commit/8bc586d6f767240e9ffa582f45a9ad11de47ecfb
WARNING: multiple messages have this Message-ID (diff)
From: panand@redhat.com (Pratyush Anand) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v11 3/9] arm64: add copy_to/from_user to kprobes blacklist Date: Wed, 16 Mar 2016 11:13:56 +0530 [thread overview] Message-ID: <20160316054329.GC28915@dhcppc6.redhat.com> (raw) In-Reply-To: <56E858D8.8030300@arm.com> On 15/03/2016:06:47:52 PM, James Morse wrote: > Hi David, > > On 09/03/16 05:32, David Long wrote: > > From: "David A. Long" <dave.long@linaro.org> > > diff --git a/arch/arm64/lib/copy_from_user.S b/arch/arm64/lib/copy_from_user.S > > index 4699cd7..0ac2131 100644 > > --- a/arch/arm64/lib/copy_from_user.S > > +++ b/arch/arm64/lib/copy_from_user.S > > @@ -66,6 +66,7 @@ > > .endm > > > > end .req x5 > > + .section .kprobes.text,"ax",%progbits > > ENTRY(__copy_from_user) > > ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(0)), ARM64_HAS_PAN, \ > > CONFIG_ARM64_PAN) > > diff --git a/arch/arm64/lib/copy_to_user.S b/arch/arm64/lib/copy_to_user.S > > index 7512bbb..e4eb84c 100644 > > --- a/arch/arm64/lib/copy_to_user.S > > +++ b/arch/arm64/lib/copy_to_user.S > > @@ -65,6 +65,7 @@ > > .endm > > > > end .req x5 > > + .section .kprobes.text,"ax",%progbits > > ENTRY(__copy_to_user) > > ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(0)), ARM64_HAS_PAN, \ > > CONFIG_ARM64_PAN) > > > > If I understand this correctly - you can't kprobe these ldr/str instructions as > the fault handler wouldn't find kprobe's out-of line version of the instruction > in the exception table... but why only these two functions? (for library > functions, we also have clear_user() and copy_in_user()...) May be not clear_user() because those are inlined, but may be __clear_user(). There can be many other functions (see [1], [2] and can be many more) which need to be blacklisted, but I think they can always be added latter on, and atleast this aspect should not hinder inclusion of these patches. > > The get_user()/put_user() stuff in uaccess.h gets inlined all over the kernel, I > don't think its feasible to put all of these in a separate section. Yes, It does not seem possible to blacklist inlined functions. There can be some other places like valid kprobable instructions in atomic context, .word instruction having data as valid instruction, etc... So, probably its not possible to make 100% safe, but yes wherever possible, we should take care. Infact, other ARCHs are also not completely safe. One can try to instrument kprobe on all the symbols in Kallsyms on an x86_64 machine and kernel crashes. > > Is it feasible to search the exception table at runtime instead? If an > address-to-be-kprobed appears in the list, we know it could generate exceptions, > so we should report that we can't probe this address. That would catch all of > the library functions, all the places uaccess.h was inlined, and anything new > that gets invented in the future. Sorry, probably I could not get it. How can an inlined addresses range be placed in exception table or any other code area. ~Pratyush [1] https://github.com/pratyushanand/linux/commit/855bc4dbb98ceafac4c933e00d203b1cd7ee9ca4 [2] https://github.com/pratyushanand/linux/commit/8bc586d6f767240e9ffa582f45a9ad11de47ecfb
next prev parent reply other threads:[~2016-03-16 5:44 UTC|newest] Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-03-09 5:32 [PATCH v11 0/9] arm64: Add kernel probes (kprobes) support David Long 2016-03-09 5:32 ` David Long 2016-03-09 5:32 ` [PATCH v11 1/9] arm64: Add HAVE_REGS_AND_STACK_ACCESS_API feature David Long 2016-03-09 5:32 ` David Long 2016-03-11 18:07 ` James Morse 2016-03-11 18:07 ` James Morse 2016-03-18 13:06 ` David Long 2016-03-18 13:06 ` David Long 2016-03-15 11:04 ` Marc Zyngier 2016-03-15 11:04 ` Marc Zyngier 2016-03-21 7:08 ` David Long 2016-03-21 7:08 ` David Long 2016-03-09 5:32 ` [PATCH v11 2/9] arm64: Add more test functions to insn.c David Long 2016-03-09 5:32 ` David Long 2016-03-09 5:32 ` [PATCH v11 3/9] arm64: add copy_to/from_user to kprobes blacklist David Long 2016-03-09 5:32 ` David Long 2016-03-15 18:47 ` James Morse 2016-03-15 18:47 ` James Morse 2016-03-16 5:43 ` Pratyush Anand [this message] 2016-03-16 5:43 ` Pratyush Anand 2016-03-16 10:27 ` James Morse 2016-03-16 10:27 ` James Morse 2016-03-17 7:57 ` Pratyush Anand 2016-03-17 7:57 ` Pratyush Anand 2016-03-18 13:29 ` Pratyush Anand 2016-03-18 13:29 ` Pratyush Anand 2016-03-18 14:02 ` James Morse 2016-03-18 14:02 ` James Morse 2016-03-18 14:43 ` Pratyush Anand 2016-03-18 14:43 ` Pratyush Anand 2016-03-18 18:12 ` James Morse 2016-03-18 18:12 ` James Morse 2016-03-21 5:17 ` Pratyush Anand 2016-03-21 5:17 ` Pratyush Anand 2016-03-21 14:52 ` Will Deacon 2016-03-21 14:52 ` Will Deacon 2016-03-22 16:51 ` Pratyush Anand 2016-03-22 16:51 ` Pratyush Anand 2016-03-17 12:04 ` 平松雅巳 / HIRAMATU,MASAMI 2016-03-17 12:04 ` 平松雅巳 / HIRAMATU,MASAMI 2016-03-09 5:32 ` [PATCH v11 4/9] arm64: add conditional instruction simulation support David Long 2016-03-09 5:32 ` David Long 2016-03-13 12:09 ` Marc Zyngier 2016-03-13 12:09 ` Marc Zyngier 2016-03-14 4:04 ` Pratyush Anand 2016-03-14 4:04 ` Pratyush Anand 2016-03-14 7:38 ` Marc Zyngier 2016-03-14 7:38 ` Marc Zyngier 2016-03-21 8:35 ` David Long 2016-03-21 8:35 ` David Long 2016-03-09 5:32 ` [PATCH v11 5/9] arm64: Kprobes with single stepping support David Long 2016-03-09 5:32 ` David Long 2016-04-20 1:29 ` Li Bin 2016-04-20 1:29 ` Li Bin 2016-03-09 5:32 ` [PATCH v11 6/9] arm64: kprobes instruction simulation support David Long 2016-03-09 5:32 ` David Long 2016-03-12 3:56 ` Marc Zyngier 2016-03-12 3:56 ` Marc Zyngier 2016-03-21 9:39 ` David Long 2016-03-21 9:39 ` David Long 2016-03-09 5:32 ` [PATCH v11 7/9] arm64: Add trampoline code for kretprobes David Long 2016-03-09 5:32 ` David Long 2016-03-13 13:52 ` Marc Zyngier 2016-03-13 13:52 ` Marc Zyngier 2016-03-21 13:30 ` David Long 2016-03-21 13:30 ` David Long 2016-03-09 5:32 ` [PATCH v11 8/9] arm64: Add kernel return probes support (kretprobes) David Long 2016-03-09 5:32 ` David Long 2016-03-17 12:22 ` 平松雅巳 / HIRAMATU,MASAMI 2016-03-17 12:22 ` 平松雅巳 / HIRAMATU,MASAMI 2016-03-17 12:58 ` 平松雅巳 / HIRAMATU,MASAMI 2016-03-17 12:58 ` 平松雅巳 / HIRAMATU,MASAMI 2016-03-21 13:33 ` David Long 2016-03-21 13:33 ` David Long 2016-03-09 5:32 ` [PATCH v11 9/9] kprobes: Add arm64 case in kprobe example module David Long 2016-03-09 5:32 ` David Long
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20160316054329.GC28915@dhcppc6.redhat.com \ --to=panand@redhat.com \ --cc=Dave.Martin@arm.com \ --cc=Robin.Murphy@arm.com \ --cc=Vladimir.Murzin@arm.com \ --cc=akpm@linux-foundation.org \ --cc=alex.bennee@linaro.org \ --cc=ard.biesheuvel@linaro.org \ --cc=broonie@kernel.org \ --cc=bshanmugam@apm.com \ --cc=catalin.marinas@arm.com \ --cc=christoffer.dall@linaro.org \ --cc=dave.long@linaro.org \ --cc=fkan@apm.com \ --cc=gregkh@linuxfoundation.org \ --cc=james.morse@arm.com \ --cc=jens.wiklander@linaro.org \ --cc=john.blackwood@ccur.com \ --cc=keescook@chromium.org \ --cc=linux-arm-kernel@lists.infradead.org \ --cc=linux-kernel@vger.kernel.org \ --cc=marc.zyngier@arm.com \ --cc=mark.rutland@arm.com \ --cc=pmladek@suse.com \ --cc=salyzyn@android.com \ --cc=sandeepa.s.prabhu@gmail.com \ --cc=steve.capper@linaro.org \ --cc=suzuki.poulose@arm.com \ --cc=viresh.kumar@linaro.org \ --cc=wcohen@redhat.com \ --cc=will.deacon@arm.com \ --cc=yang.shi@linaro.org \ --cc=zlim.lnx@gmail.com \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.