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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 2 Apr 2020 17:15:58 +0100 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 032GGGQv57606340 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 2 Apr 2020 16:16:16 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1BB3AA4054; Thu, 2 Apr 2020 16:16:16 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A74A7A405B; Thu, 2 Apr 2020 16:16:15 +0000 (GMT) Received: from localhost (unknown [9.85.74.67]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 2 Apr 2020 16:16:15 +0000 (GMT) Date: Thu, 02 Apr 2020 21:46:12 +0530 From: "Naveen N. Rao" Subject: Re: [PATCH v8 2/7] powerpc/kprobes: Mark newly allocated probes as RO To: linuxppc-dev@lists.ozlabs.org, Russell Currey References: <20200402084053.188537-1-ruscur@russell.cc> <20200402084053.188537-2-ruscur@russell.cc> In-Reply-To: <20200402084053.188537-2-ruscur@russell.cc> MIME-Version: 1.0 User-Agent: astroid/v0.15-13-gb675b421 (https://github.com/astroidmail/astroid) Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 x-cbid: 20040216-0020-0000-0000-000003C05099 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20040216-0021-0000-0000-00002218FCDC Message-Id: <1585844035.o235bvxmq0.naveen@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.676 definitions=2020-04-02_06:2020-04-02, 2020-04-02 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 impostorscore=0 suspectscore=0 adultscore=0 priorityscore=1501 mlxscore=0 lowpriorityscore=0 clxscore=1015 spamscore=0 mlxlogscore=999 malwarescore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004020131 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kernel-hardening@lists.openwall.com, ajd@linux.ibm.com, npiggin@gmail.com, dja@axtens.net Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Russell Currey wrote: > With CONFIG_STRICT_KERNEL_RWX=3Dy and CONFIG_KPROBES=3Dy, there will be o= ne > W+X page at boot by default. This can be tested with > CONFIG_PPC_PTDUMP=3Dy and CONFIG_PPC_DEBUG_WX=3Dy set, and checking the > kernel log during boot. >=20 > powerpc doesn't implement its own alloc() for kprobes like other > architectures do, but we couldn't immediately mark RO anyway since we do > a memcpy to the page we allocate later. After that, nothing should be > allowed to modify the page, and write permissions are removed well > before the kprobe is armed. >=20 > The memcpy() would fail if >1 probes were allocated, so use > patch_instruction() instead which is safe for RO. >=20 > Reviewed-by: Daniel Axtens > Signed-off-by: Russell Currey > Signed-off-by: Christophe Leroy > --- > arch/powerpc/kernel/kprobes.c | 17 +++++++++++++---- > 1 file changed, 13 insertions(+), 4 deletions(-) >=20 > diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.= c > index 81efb605113e..fa4502b4de35 100644 > --- a/arch/powerpc/kernel/kprobes.c > +++ b/arch/powerpc/kernel/kprobes.c > @@ -24,6 +24,8 @@ > #include > #include > #include > +#include > +#include > =20 > DEFINE_PER_CPU(struct kprobe *, current_kprobe) =3D NULL; > DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); > @@ -102,6 +104,16 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name= , unsigned int offset) > return addr; > } > =20 > +void *alloc_insn_page(void) > +{ > + void *page =3D vmalloc_exec(PAGE_SIZE); > + > + if (page) > + set_memory_ro((unsigned long)page, 1); > + > + return page; > +} > + This crashes for me with KPROBES_SANITY_TEST during the kretprobe test. =20 It seems to be handling the kretprobe itself properly, but seems to=20 crash on the return path. I haven't yet been able to work out what's=20 going wrong. [ 0.517880] Kprobe smoke test: started [ 0.626680] Oops: Exception in kernel mode, sig: 4 [#1] [ 0.626708] LE PAGE_SIZE=3D64K MMU=3DRadix SMP NR_CPUS=3D2048 NUMA Power= NV [ 0.626735] Modules linked in: [ 0.626760] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.6.0-06592-g2e646= 94b9137 #51 [ 0.626795] NIP: c008000000020000 LR: c00000000021ce34 CTR: c0000000002= 1c5f8 [ 0.626829] REGS: c0000000fd3e3860 TRAP: 0e40 Not tainted (5.6.0-0659= 2-g2e64694b9137) [ 0.626862] MSR: 9000000002089433 CR:= 28000284 XER: 00040000 [ 0.626922] CFAR: c00000000000ef20 IRQMASK: 0=20 [ 0.626922] GPR00: c000000000052250 c0000000fd3e3af0 c000000002330200 00= 0000002db8ad86=20 [ 0.626922] GPR04: 0000000000000000 c00000000006ba3c 0000000000000800 c0= 000000fd3a0000=20 [ 0.626922] GPR08: 0000000000000000 ffffffffaaaaaaab c0000000fd3a0000 00= 00000040000000=20 [ 0.626922] GPR12: c00000000021c5f0 c000000002520000 c000000000011790 00= 00000000000000=20 [ 0.626922] GPR16: 0000000000000000 0000000000000000 0000000000000000 00= 00000000000000=20 [ 0.626922] GPR20: 0000000000000000 0000000000000000 0000000000000000 00= 00000000000000=20 [ 0.626922] GPR24: c0000000020034bc c0000000012068b8 c000000002062e50 c0= 000000fd2319a0=20 [ 0.626922] GPR28: c000000000f5ebb0 0000000000000000 c0000000021bc278 c0= 00000002458540=20 [ 0.627234] NIP [c008000000020000] 0xc008000000020000 [ 0.627264] LR [c00000000021ce34] init_test_probes+0x424/0x560 [ 0.627291] Call Trace: [ 0.627313] [c0000000fd3e3af0] [c00000000021ce34] init_test_probes+0x424= /0x560 (unreliable) [ 0.627356] [c0000000fd3e3b90] [c00000000202de2c] init_kprobes+0x1a8/0x1= c8 [ 0.627392] [c0000000fd3e3c00] [c000000000011140] do_one_initcall+0x60/0= x2b0 [ 0.627432] [c0000000fd3e3cd0] [c000000002004674] kernel_init_freeable+0= x2e0/0x3a0 [ 0.627471] [c0000000fd3e3db0] [c0000000000117ac] kernel_init+0x24/0x178 [ 0.627510] [c0000000fd3e3e20] [c00000000000c7a8] ret_from_kernel_thread= +0x5c/0x74 [ 0.627543] Instruction dump: [ 0.627562] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXX= XX XXXXXXXX=20 [ 0.627607] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX <00000000> 00000000 0000= 0000 00000000=20 [ 0.627660] ---[ end trace 964ab92781f5d99d ]--- [ 0.629607]=20 - Naveen