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From: Ilya Smith In-Reply-To: <20180330095735.GA15641@amd> Date: Fri, 30 Mar 2018 14:10:21 +0300 Cc: rth@twiddle.net, ink@jurassic.park.msu.ru, mattst88@gmail.com, vgupta@synopsys.com, linux@armlinux.org.uk, tony.luck@intel.com, fenghua.yu@intel.com, jhogan@kernel.org, ralf@linux-mips.org, jejb@parisc-linux.org, Helge Deller , benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, nyc@holomorphy.com, viro@zeniv.linux.org.uk, arnd@arndb.de, gregkh@linuxfoundation.org, deepa.kernel@gmail.com, Michal Hocko , hughd@google.com, kstewart@linuxfoundation.org, pombredanne@nexb.com, akpm@linux-foundation.org, steve.capper@arm.com, punit.agrawal@arm.com, paul.burton@mips.com, aneesh.kumar@linux.vnet.ibm.com, npiggin@gmail.com, keescook@chromium.org, bhsharma@redhat.com, riel@redhat.com, nitin.m.gupta@oracle.com, kirill.shutemov@linux.intel.com, dan.j.williams@intel.com, jack@suse.cz, ross.zwisler@linux.intel.com, jglisse@redhat.com, willy@infradead.org, aarcange@redhat.com, oleg@redhat.com, linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-metag@vger.kernel.org, linux-mips@linux-mips.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-mm@kvack.org Content-Transfer-Encoding: quoted-printable Message-Id: <4F529F89-6595-4DE9-87C2-C3D971C76658@gmail.com> References: <1521736598-12812-1-git-send-email-blackzert@gmail.com> <20180330075508.GA21798@amd> <95EECC28-7349-4FB4-88BF-26E4CF087A0B@gmail.com> <20180330095735.GA15641@amd> To: Pavel Machek X-Mailer: Apple Mail (2.3445.5.20) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1595656488556903336?= X-GMAIL-MSGID: =?utf-8?q?1596360726944205959?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: > On 30 Mar 2018, at 12:57, Pavel Machek wrote: >=20 > On Fri 2018-03-30 12:07:58, Ilya Smith wrote: >> Hi >>=20 >>> On 30 Mar 2018, at 10:55, Pavel Machek wrote: >>>=20 >>> Hi! >>>=20 >>>> Current implementation doesn't randomize address returned by mmap. >>>> All the entropy ends with choosing mmap_base_addr at the process >>>> creation. After that mmap build very predictable layout of address >>>> space. It allows to bypass ASLR in many cases. This patch make >>>> randomization of address on any mmap call. >>>=20 >>> How will this interact with people debugging their application, and >>> getting different behaviours based on memory layout? >>>=20 >>> strace, strace again, get different results? >>>=20 >>=20 >> Honestly I=E2=80=99m confused about your question. If the only one = way for debugging=20 >> application is to use predictable mmap behaviour, then something went = wrong in=20 >> this live and we should stop using computers at all. >=20 > I'm not saying "only way". I'm saying one way, and you are breaking > that. There's advanced stuff like debuggers going "back in time". >=20 Correct me if I wrong, when you run gdb for instance and try to debug = some=20 application, gdb will disable randomization. This behaviour works with = gdb=20 command: set disable-randomization on. As I know, gdb remove flag = PF_RANDOMIZE=20 from current personality thats how it disables ASLR for debugging = process.=20 According to my patch, flag PF_RANDOMIZE is checked before calling=20 unmapped_area_random. So I don=E2=80=99t breaking debugging. If you = talking about the=20 case, when your application crashes under customer environment and you = want to debug it; in this case layout of memory is what you don=E2=80=99t = control at all and=20 you have to understand what is where. So for debugging memory process = layout is not what you should care of. Thanks, Ilya