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[PATCH 4.9 07/44] powerpc/perf: Fix oops when kthread execs user process

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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>

commit bf05fc25f268cd62f147f368fe65ad3e5b04fe9f upstream.

When a kthread calls call_usermodehelper() the steps are:
  1. allocate current->mm
  2. load_elf_binary()
  3. populate 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 1 has completed
but not yet reached to step 3) and if perf tries to read userspace
regs, kernel oops with following log:

  Unable to handle kernel paging request for data at address 0x00000000
  Faulting instruction address: 0xc0000000000da0fc
  ...
  Call Trace:
  perf_output_sample_regs+0x6c/0xd0
  perf_output_sample+0x4e4/0x830
  perf_event_output_forward+0x64/0x90
  __perf_event_overflow+0x8c/0x1e0
  record_and_restart+0x220/0x5c0
  perf_event_interrupt+0x2d8/0x4d0
  performance_monitor_exception+0x54/0x70
  performance_monitor_common+0x158/0x160
  --- interrupt: f01 at avtab_search_node+0x150/0x1a0
      LR = avtab_search_node+0x100/0x1a0
  ...
  load_elf_binary+0x6e8/0x15a0
  search_binary_handler+0xe8/0x290
  do_execveat_common.isra.14+0x5f4/0x840
  call_usermodehelper_exec_async+0x170/0x210
  ret_from_kernel_thread+0x5c/0x7c

Fix it by setting abi to PERF_SAMPLE_REGS_ABI_NONE when userspace
pt_regs are not set.

Fixes: ed4a4ef85cf5 ("powerpc/perf: Add support for sampling interrupt register state")
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/powerpc/perf/perf_regs.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/powerpc/perf/perf_regs.c
+++ b/arch/powerpc/perf/perf_regs.c
@@ -100,5 +100,6 @@ void perf_get_regs_user(struct perf_regs
 			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;
 }

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[PATCH 4.9 00/44] 4.9.35-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:20 +0200
  [PATCH 4.9 16/44] HID: Add quirk for Dell PIXART OEM mouse Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:20 +0200
  [PATCH 4.9 14/44] CIFS: Improve readdir verbosity Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:20 +0200
  [PATCH 4.9 42/44] net: phy: fix marvell phy status reading Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:20 +0200
  [PATCH 4.9 10/44] perf/x86/intel: Add 1G DTLB load/store miss support for SKL Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:20 +0200
  [PATCH 4.9 07/44] powerpc/perf: Fix oops when kthread execs user process Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:20 +0200
  [PATCH 4.9 11/44] KVM: s390: gaccess: fix real-space designation asce handling for gmap shadows Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:20 +0200
  [PATCH 4.9 21/44] brcmfmac: add parameter to pass error code in firmware callback Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:20 +0200
  [PATCH 4.9 37/44] usb: gadget: f_fs: avoid out of bounds access on comp_desc Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:20 +0200
  [PATCH 4.9 15/44] cxgb4: notify uP to route ctrlq compl to rdma rspq Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:20 +0200
  [PATCH 4.9 35/44] of: Add check to of_scan_flat_dt() before accessing initial_boot_params Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 06/44] fs/exec.c: account for argv/envp pointers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 27/44] target: Fix kref->refcount underflow in transport_cmd_finish_abort Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 12/44] KVM: PPC: Book3S HV: Preserve userspace HTM state properly Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 03/44] xen-blkback: dont leak stack data via response ring Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 09/44] lib/cmdline.c: fix get_options() overflow while parsing ranges Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 23/44] brcmfmac: unbind all devices upon failure in firmware callback Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 38/44] rt2x00: avoid introducing a USB dependency in the rt2x00lib module Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 28/44] iscsi-target: Fix delayed logout processing greater than SECONDS_FOR_LOGOUT_COMP Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 05/44] ALSA: pcm: Dont treat NULL chmap as a fatal error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 30/44] drm/radeon: add a PX quirk for another K53TK variant Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 26/44] arm64/vdso: Fix nsec handling for CLOCK_MONOTONIC_RAW Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 22/44] brcmfmac: use firmware callback upon failure to load Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 04/44] ALSA: firewire-lib: Fix stall of process context at packet error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 08/44] autofs: sanity check status reported with AUTOFS_DEV_IOCTL_FAIL Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 40/44] dmaengine: bcm2835: Fix cyclic DMA period splitting Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 31/44] drm/radeon: add a quirk for Toshiba Satellite L20-183 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 19/44] powerpc/64s: Handle data breakpoints in Radix mode Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 39/44] net: phy: Initialize mdio clock at probe function Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 25/44] time: Fix CLOCK_MONOTONIC_RAW sub-nanosecond accounting Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 29/44] iscsi-target: Reject immediate data underflow larger than SCSI transfer length Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:40 +0200
  [PATCH 4.9 20/44] Input: i8042 - add Fujitsu Lifebook AH544 to notimeout list Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:50 +0200
  [PATCH 4.9 18/44] powerpc/kprobes: Pause function_graph tracing during jprobes handling Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 16:50 +0200
  Re: [PATCH 4.9 00/44] 4.9.35-stable review Sumit Semwal <sumit.semwal@linaro.org> - 2017-06-27 19:40 +0200
    Re: [PATCH 4.9 00/44] 4.9.35-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-28 14:10 +0200
  Re: [PATCH 4.9 00/44] 4.9.35-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 20:40 +0200
  Re: [PATCH 4.9 00/44] 4.9.35-stable review Guenter Roeck <linux@roeck-us.net> - 2017-06-27 21:10 +0200
  Re: [PATCH 4.9 00/44] 4.9.35-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-06-28 16:00 +0200

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