The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From a2308c11ecbc3471ebb7435ee8075815b1502ef0 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <heiko.carstens(a)de.ibm.com>
Date: Mon, 18 Nov 2019 13:09:52 +0100
Subject: [PATCH] s390/smp,vdso: fix ASCE handling
When a secondary CPU is brought up it must initialize its control
registers. CPU A which triggers that a secondary CPU B is brought up
stores its control register contents into the lowcore of new CPU B,
which then loads these values on startup.
This is problematic in various ways: the control register which
contains the home space ASCE will correctly contain the kernel ASCE;
however control registers for primary and secondary ASCEs are
initialized with whatever values were present in CPU A.
Typically:
- the primary ASCE will contain the user process ASCE of the process
that triggered onlining of CPU B.
- the secondary ASCE will contain the percpu VDSO ASCE of CPU A.
Due to lazy ASCE handling we may also end up with other combinations.
When then CPU B switches to a different process (!= idle) it will
fixup the primary ASCE. However the problem is that the (wrong) ASCE
from CPU A was loaded into control register 1: as soon as an ASCE is
attached (aka loaded) a CPU is free to generate TLB entries using that
address space.
Even though it is very unlikey that CPU B will actually generate such
entries, this could result in TLB entries of the address space of the
process that ran on CPU A. These entries shouldn't exist at all and
could cause problems later on.
Furthermore the secondary ASCE of CPU B will not be updated correctly.
This means that processes may see wrong results or even crash if they
access VDSO data on CPU B. The correct VDSO ASCE will eventually be
loaded on return to user space as soon as the kernel executed a call
to strnlen_user or an atomic futex operation on CPU B.
Fix both issues by intializing the to be loaded control register
contents with the correct ASCEs and also enforce (re-)loading of the
ASCEs upon first context switch and return to user space.
Fixes: 0aaba41b58bc ("s390: remove all code using the access register mode")
Cc: stable(a)vger.kernel.org # v4.15+
Signed-off-by: Heiko Carstens <heiko.carstens(a)de.ibm.com>
Signed-off-by: Vasily Gorbik <gor(a)linux.ibm.com>
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 6acdcf1d4074..06dddd7c4290 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -262,10 +262,13 @@ static void pcpu_prepare_secondary(struct pcpu *pcpu, int cpu)
lc->spinlock_index = 0;
lc->percpu_offset = __per_cpu_offset[cpu];
lc->kernel_asce = S390_lowcore.kernel_asce;
+ lc->user_asce = S390_lowcore.kernel_asce;
lc->machine_flags = S390_lowcore.machine_flags;
lc->user_timer = lc->system_timer =
lc->steal_timer = lc->avg_steal_timer = 0;
__ctl_store(lc->cregs_save_area, 0, 15);
+ lc->cregs_save_area[1] = lc->kernel_asce;
+ lc->cregs_save_area[7] = lc->vdso_asce;
save_access_regs((unsigned int *) lc->access_regs_save_area);
memcpy(lc->stfle_fac_list, S390_lowcore.stfle_fac_list,
sizeof(lc->stfle_fac_list));
@@ -844,6 +847,8 @@ static void smp_init_secondary(void)
S390_lowcore.last_update_clock = get_tod_clock();
restore_access_regs(S390_lowcore.access_regs_save_area);
+ set_cpu_flag(CIF_ASCE_PRIMARY);
+ set_cpu_flag(CIF_ASCE_SECONDARY);
cpu_init();
preempt_disable();
init_cpu_timer();
From: Leo Yan <leo.yan(a)linaro.org>
The test case 'Read backward ring buffer' failed on 32-bit architectures
which were found by LKFT perf testing. The test failed on arm32 x15
device, qemu_arm32, qemu_i386, and found intermittent failure on i386;
the failure log is as below:
50: Read backward ring buffer :
--- start ---
test child forked, pid 510
Using CPUID GenuineIntel-6-9E-9
mmap size 1052672B
mmap size 8192B
Finished reading overwrite ring buffer: rewind
free(): invalid next size (fast)
test child interrupted
---- end ----
Read backward ring buffer: FAILED!
The log hints there have issue for memory usage, thus free() reports
error 'invalid next size' and directly exit for the case. Finally, this
issue is root caused as out of bounds memory access for the data array
'evsel->id'.
The backward ring buffer test invokes do_test() twice. 'evsel->id' is
allocated at the first call with the flow:
test__backward_ring_buffer()
`-> do_test()
`-> evlist__mmap()
`-> evlist__mmap_ex()
`-> perf_evsel__alloc_id()
So 'evsel->id' is allocated with one item, and it will be used in
function perf_evlist__id_add():
evsel->id[0] = id
evsel->ids = 1
At the second call for do_test(), it skips to initialize 'evsel->id'
and reuses the array which is allocated in the first call. But
'evsel->ids' contains the stale value. Thus:
evsel->id[1] = id -> out of bound access
evsel->ids = 2
To fix this issue, we will use evlist__open() and evlist__close() pair
functions to prepare and cleanup context for evlist; so 'evsel->id' and
'evsel->ids' can be initialized properly when invoke do_test() and avoid
the out of bounds memory access.
Fixes: ee74701ed8ad ("perf tests: Add test to check backward ring buffer")
Signed-off-by: Leo Yan <leo.yan(a)linaro.org>
Reviewed-by: Jiri Olsa <jolsa(a)kernel.org>
Cc: Alexander Shishkin <alexander.shishkin(a)linux.intel.com>
Cc: Mark Rutland <mark.rutland(a)arm.com>
Cc: Namhyung Kim <namhyung(a)kernel.org>
Cc: Naresh Kamboju <naresh.kamboju(a)linaro.org>
Cc: Peter Zijlstra <peterz(a)infradead.org>
Cc: Wang Nan <wangnan0(a)huawei.com>
Cc: stable(a)vger.kernel.org # v4.10+
Link: http://lore.kernel.org/lkml/20191107020244.2427-1-leo.yan@linaro.org
Signed-off-by: Arnaldo Carvalho de Melo <acme(a)redhat.com>
---
tools/perf/tests/backward-ring-buffer.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/tools/perf/tests/backward-ring-buffer.c b/tools/perf/tests/backward-ring-buffer.c
index a4cd30c0beb3..15cea518f5ad 100644
--- a/tools/perf/tests/backward-ring-buffer.c
+++ b/tools/perf/tests/backward-ring-buffer.c
@@ -148,6 +148,15 @@ int test__backward_ring_buffer(struct test *test __maybe_unused, int subtest __m
goto out_delete_evlist;
}
+ evlist__close(evlist);
+
+ err = evlist__open(evlist);
+ if (err < 0) {
+ pr_debug("perf_evlist__open: %s\n",
+ str_error_r(errno, sbuf, sizeof(sbuf)));
+ goto out_delete_evlist;
+ }
+
err = do_test(evlist, 1, &sample_count, &comm_count);
if (err != TEST_OK)
goto out_delete_evlist;
--
2.21.0