From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3wpPvC5LXdzDqL8 for ; Thu, 15 Jun 2017 23:47:19 +1000 (AEST) Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v5FDhn40041358 for ; Thu, 15 Jun 2017 09:47:16 -0400 Received: from e23smtp02.au.ibm.com (e23smtp02.au.ibm.com [202.81.31.144]) by mx0b-001b2d01.pphosted.com with ESMTP id 2b3ep5y34x-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 15 Jun 2017 09:47:16 -0400 Received: from localhost by e23smtp02.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 15 Jun 2017 23:47:13 +1000 Received: from d23av04.au.ibm.com (d23av04.au.ibm.com [9.190.235.139]) by d23relay08.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v5FDlBhu65929462 for ; Thu, 15 Jun 2017 23:47:11 +1000 Received: from d23av04.au.ibm.com (localhost [127.0.0.1]) by d23av04.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id v5FDl8j2022773 for ; Thu, 15 Jun 2017 23:47:09 +1000 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 Message-Id: <1497534408-4591-1-git-send-email-ravi.bangoria@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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