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linux/arch/powerpc/perf
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Athira Rajeev 5ae5fbd210 powerpc/perf: Fix handling of privilege level checks in perf interrupt context 
Running "perf mem record" in powerpc platforms with selinux enabled
resulted in soft lockup's. Below call-trace was seen in the logs:

  CPU: 58 PID: 3751 Comm: sssd_nss Not tainted 5.11.0-rc7+ #2
  NIP:  c000000000dff3d4 LR: c000000000dff3d0 CTR: 0000000000000000
  REGS: c000007fffab7d60 TRAP: 0100   Not tainted  (5.11.0-rc7+)
  ...
  NIP _raw_spin_lock_irqsave+0x94/0x120
  LR  _raw_spin_lock_irqsave+0x90/0x120
  Call Trace:
    0xc00000000fd47260 (unreliable)
    skb_queue_tail+0x3c/0x90
    audit_log_end+0x6c/0x180
    common_lsm_audit+0xb0/0xe0
    slow_avc_audit+0xa4/0x110
    avc_has_perm+0x1c4/0x260
    selinux_perf_event_open+0x74/0xd0
    security_perf_event_open+0x68/0xc0
    record_and_restart+0x6e8/0x7f0
    perf_event_interrupt+0x22c/0x560
    performance_monitor_exception0x4c/0x60
    performance_monitor_common_virt+0x1c8/0x1d0
  interrupt: f00 at _raw_spin_lock_irqsave+0x38/0x120
  NIP:  c000000000dff378 LR: c000000000b5fbbc CTR: c0000000007d47f0
  REGS: c00000000fd47860 TRAP: 0f00   Not tainted  (5.11.0-rc7+)
  ...
  NIP _raw_spin_lock_irqsave+0x38/0x120
  LR  skb_queue_tail+0x3c/0x90
  interrupt: f00
    0x38 (unreliable)
    0xc00000000aae6200
    audit_log_end+0x6c/0x180
    audit_log_exit+0x344/0xf80
    __audit_syscall_exit+0x2c0/0x320
    do_syscall_trace_leave+0x148/0x200
    syscall_exit_prepare+0x324/0x390
    system_call_common+0xfc/0x27c

The above trace shows that while the CPU was handling a performance
monitor exception, there was a call to security_perf_event_open()
function. In powerpc core-book3s, this function is called from
perf_allow_kernel() check during recording of data address in the
sample via perf_get_data_addr().

Commit da97e18458 ("perf_event: Add support for LSM and SELinux
checks") introduced security enhancements to perf. As part of this
commit, the new security hook for perf_event_open() was added in all
places where perf paranoid check was previously used. In powerpc
core-book3s code, originally had paranoid checks in
perf_get_data_addr() and power_pmu_bhrb_read(). So
perf_paranoid_kernel() checks were replaced with perf_allow_kernel()
in these PMU helper functions as well.

The intention of paranoid checks in core-book3s was to verify
privilege access before capturing some of the sample data. Along with
paranoid checks, perf_allow_kernel() also does a
security_perf_event_open(). Since these functions are accessed while
recording a sample, we end up calling selinux_perf_event_open() in PMI
context. Some of the security functions use spinlock like
sidtab_sid2str_put(). If a perf interrupt hits under a spin lock and
if we end up in calling selinux hook functions in PMI handler, this
could cause a dead lock.

Since the purpose of this security hook is to control access to
perf_event_open(), it is not right to call this in interrupt context.

The paranoid checks in powerpc core-book3s were done at interrupt time
which is also not correct.

Reference commits:
  Commit cd1231d703 ("powerpc/perf: Prevent kernel address leak via perf_get_data_addr()")
  Commit bb19af8160 ("powerpc/perf: Prevent kernel address leak to userspace via BHRB buffer")

We only allow creation of events that have already passed the
privilege checks in perf_event_open(). So these paranoid checks are
not needed at event time. As a fix, patch uses
'event->attr.exclude_kernel' check to prevent exposing kernel address
for userspace only sampling.

Fixes: cd1231d703 ("powerpc/perf: Prevent kernel address leak via perf_get_data_addr()")
Cc: stable@vger.kernel.org # v4.17+
Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1614247839-1428-1-git-send-email-atrajeev@linux.vnet.ibm.com
2021-03-02 22:41:51 +11:00
..
req-gen powerpc: clean the inclusion of stringify.h 2018-07-30 22:48:17 +10:00
8xx-pmu.c powerpc/ppc-opcode: Add PPC_RAW_MFSPR() 2020-12-09 23:48:13 +11:00
bhrb.S treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
callchain_32.c powerpc/vdso: Retrieve sigtramp offsets at buildtime 2020-12-04 01:01:17 +11:00
callchain_64.c powerpc/vdso: Retrieve sigtramp offsets at buildtime 2020-12-04 01:01:17 +11:00
callchain.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
callchain.h powerpc/64s/perf: perf interrupt does not have to get_user_pages to access user memory 2020-11-19 16:56:52 +11:00
core-book3s.c powerpc/perf: Fix handling of privilege level checks in perf interrupt context 2021-03-02 22:41:51 +11:00
core-fsl-emb.c powerpc/perf: move perf irq/nmi handling details into traps.c 2021-02-09 00:02:10 +11:00
e500-pmu.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
e6500-pmu.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
generic-compat-pmu.c powerpc/perf: Update Power PMU cache_events to u64 type 2020-07-22 21:56:40 +10:00
hv-24x7-catalog.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
hv-24x7-domains.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
hv-24x7.c powerpc/perf/hv-24x7: Dont create sysfs event files for dummy events 2021-01-30 11:39:25 +11:00
hv-24x7.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
hv-common.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
hv-common.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
hv-gpci-requests.h powerpc/perf/hv-gpci: Fix starting index value 2020-10-07 22:34:48 +11:00
hv-gpci.c powerpc/hv-gpci: Add sysfs files inside hv-gpci device to show cpumask 2020-10-07 22:34:49 +11:00
hv-gpci.h powerpc/perf: consolidate GPCI hcall structs into asm/hvcall.h 2020-09-02 11:00:20 +10:00
imc-pmu.c powerpc: fix -Wimplicit-fallthrough 2020-11-18 14:18:09 -06:00
internal.h powerpc/perf: power10 Performance Monitoring support 2020-07-22 21:56:41 +10:00
isa207-common.c powerpc/perf: Adds support for programming of Thresholding in P10 2021-02-11 23:35:36 +11:00
isa207-common.h powerpc/perf: Adds support for programming of Thresholding in P10 2021-02-11 23:35:36 +11:00
Makefile powerpc/perf: power10 Performance Monitoring support 2020-07-22 21:56:41 +10:00
mpc7450-pmu.c powerpc/perf: Adds support for programming of Thresholding in P10 2021-02-11 23:35:36 +11:00
perf_regs.c powerpc/perf: Expose Performance Monitor Counter SPR's as part of extended regs 2021-02-09 01:09:44 +11:00
power5-pmu.c powerpc/perf: Adds support for programming of Thresholding in P10 2021-02-11 23:35:36 +11:00
power5+-pmu.c powerpc/perf: Adds support for programming of Thresholding in P10 2021-02-11 23:35:36 +11:00
power6-pmu.c powerpc/perf: Adds support for programming of Thresholding in P10 2021-02-11 23:35:36 +11:00
power7-events-list.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
power7-pmu.c powerpc/perf: Adds support for programming of Thresholding in P10 2021-02-11 23:35:36 +11:00
power8-events-list.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
power8-pmu.c powerpc/perf: Update Power PMU cache_events to u64 type 2020-07-22 21:56:40 +10:00
power9-events-list.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
power9-pmu.c powerpc/perf: Add support for outputting extended regs in perf intr_regs 2020-08-17 13:11:22 +10:00
power10-events-list.h powerpc/perf: Fix to update cache events with l2l3 events in power10 2020-12-04 01:01:29 +11:00
power10-pmu.c powerpc/perf: Adds support for programming of Thresholding in P10 2021-02-11 23:35:36 +11:00
ppc970-pmu.c powerpc/perf: Adds support for programming of Thresholding in P10 2021-02-11 23:35:36 +11:00