Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752204AbdFONrT (ORCPT ); Thu, 15 Jun 2017 09:47:19 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:33470 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750923AbdFONrS (ORCPT ); Thu, 15 Jun 2017 09:47:18 -0400 From: Ravi Bangoria To: mpe@ellerman.id.au Cc: benh@kernel.crashing.org, paulus@samba.org, mingo@kernel.org, peterz@infradead.org, acme@kernel.org, alexander.shishkin@linux.intel.com, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, naveen.n.rao@linux.vnet.ibm.com, Ravi Bangoria Subject: [PATCH] ppc64/perf: Fix oops when kthread execs user process Date: Thu, 15 Jun 2017 19:16:48 +0530 X-Mailer: git-send-email 2.1.4 X-TM-AS-MML: disable x-cbid: 17061513-0044-0000-0000-0000026DFCF0 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17061513-0045-0000-0000-000006FD4E6A Message-Id: <1497534408-4591-1-git-send-email-ravi.bangoria@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-06-15_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=1 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1703280000 definitions=main-1706150241 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3395 Lines: 63 When a kthread makes a call_usermodehelper() call the steps are: a. allocates current->mm b. load_elf_binary() c. populates current->thread.regs While doing this, interrupts are not disabled. If there is a perf interrupt in the middle of this process (i.e. step 'a' has completed but not yet reached to step 'c') and if perf tries to read userspace regs, kernel oops with following log: [ 131.217172] Unable to handle kernel paging request for data at address 0x00000000 [ 131.217731] Faulting instruction address: 0xc0000000000da0fc ... [ 131.235555] Call Trace: [ 131.235714] [c0000000bbaaad60] [c00000000025dedc] perf_output_sample_regs+0x6c/0xd0 [ 131.236020] [c0000000bbaaadb0] [c000000000269b44] perf_output_sample+0x4e4/0x830 [ 131.236362] [c0000000bbaaae40] [c00000000026a354] perf_event_output_forward+0x64/0x90 [ 131.236668] [c0000000bbaaaeb0] [c00000000026298c] __perf_event_overflow+0x8c/0x1e0 [ 131.236979] [c0000000bbaaaf00] [c0000000000dc330] record_and_restart+0x220/0x5c0 [ 131.237306] [c0000000bbaab230] [c0000000000dd1d8] perf_event_interrupt+0x2d8/0x4d0 [ 131.237611] [c0000000bbaab320] [c0000000000294a4] performance_monitor_exception+0x54/0x70 [ 131.237891] [c0000000bbaab350] [c00000000000a0a8] performance_monitor_common+0x158/0x160 [ 131.238208] --- interrupt: f01 at avtab_search_node+0x150/0x1a0 [ 131.238208] LR = avtab_search_node+0x100/0x1a0 [ 131.238617] [c0000000bbaab640] [c000000000526770] context_struct_compute_av+0x220/0x5b0 (unreliable) [ 131.238948] [c0000000bbaab730] [c0000000005278b4] security_compute_av+0x174/0x390 [ 131.239231] [c0000000bbaab7e0] [c0000000005050e4] avc_compute_av+0x84/0x260 [ 131.239471] [c0000000bbaab890] [c000000000506198] avc_has_perm+0xf8/0x1c0 [ 131.239708] [c0000000bbaab980] [c00000000050f32c] file_has_perm+0x6c/0xd0 [ 131.239972] [c0000000bbaab9e0] [c0000000004ff0fc] security_mmap_file+0xac/0x140 [ 131.240256] [c0000000bbaaba50] [c0000000002b1fc0] vm_mmap_pgoff+0x80/0x160 [ 131.240532] [c0000000bbaabb30] [c0000000003f7db4] elf_map+0xa4/0x180 [ 131.240771] [c0000000bbaabb90] [c0000000003f9a48] load_elf_binary+0x6e8/0x15a0 [ 131.241060] [c0000000bbaabc90] [c000000000374f58] search_binary_handler+0xe8/0x290 [ 131.241347] [c0000000bbaabd20] [c000000000375c14] do_execveat_common.isra.14+0x5f4/0x840 [ 131.241631] [c0000000bbaabdf0] [c00000000010be70] call_usermodehelper_exec_async+0x170/0x210 [ 131.241955] [c0000000bbaabe30] [c00000000000bae0] ret_from_kernel_thread+0x5c/0x7c Fix it by setting abi to PERF_SAMPLE_REGS_ABI_NONE when userspace pt_regs are not set. Signed-off-by: Ravi Bangoria --- Note: this should go to stable as well. I've not checked below 4.4 kernel but I'm able to reproduce it with 4.4 kernel. arch/powerpc/perf/perf_regs.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/perf/perf_regs.c b/arch/powerpc/perf/perf_regs.c index cbd82fd..09ceea6 100644 --- a/arch/powerpc/perf/perf_regs.c +++ b/arch/powerpc/perf/perf_regs.c @@ -101,5 +101,6 @@ void perf_get_regs_user(struct perf_regs *regs_user, struct pt_regs *regs_user_copy) { regs_user->regs = task_pt_regs(current); - regs_user->abi = perf_reg_abi(current); + regs_user->abi = (regs_user->regs) ? perf_reg_abi(current) : + PERF_SAMPLE_REGS_ABI_NONE; } -- 2.9.4