4.4-stable patches

added patches:
	perf-fix-data-race-between-pin_count-increment-decrement.patch

diff --git a/queue-4.4/perf-fix-data-race-between-pin_count-increment-decrement.patch b/queue-4.4/perf-fix-data-race-between-pin_count-increment-decrement.patch
new file mode 100644 (file)
index 0000000..53c484f
--- /dev/null
+++ b/queue-4.4/perf-fix-data-race-between-pin_count-increment-decrement.patch
@@ -0,0 +1,48 @@
+From 6c605f8371159432ec61cbb1488dcf7ad24ad19a Mon Sep 17 00:00:00 2001
+From: Marco Elver <elver@google.com>
+Date: Thu, 27 May 2021 12:47:11 +0200
+Subject: perf: Fix data race between pin_count increment/decrement
+
+From: Marco Elver <elver@google.com>
+
+commit 6c605f8371159432ec61cbb1488dcf7ad24ad19a upstream.
+
+KCSAN reports a data race between increment and decrement of pin_count:
+
+  write to 0xffff888237c2d4e0 of 4 bytes by task 15740 on cpu 1:
+   find_get_context            kernel/events/core.c:4617
+   __do_sys_perf_event_open    kernel/events/core.c:12097 [inline]
+   __se_sys_perf_event_open    kernel/events/core.c:11933
+   ...
+  read to 0xffff888237c2d4e0 of 4 bytes by task 15743 on cpu 0:
+   perf_unpin_context          kernel/events/core.c:1525 [inline]
+   __do_sys_perf_event_open    kernel/events/core.c:12328 [inline]
+   __se_sys_perf_event_open    kernel/events/core.c:11933
+   ...
+
+Because neither read-modify-write here is atomic, this can lead to one
+of the operations being lost, resulting in an inconsistent pin_count.
+Fix it by adding the missing locking in the CPU-event case.
+
+Fixes: fe4b04fa31a6 ("perf: Cure task_oncpu_function_call() races")
+Reported-by: syzbot+142c9018f5962db69c7e@syzkaller.appspotmail.com
+Signed-off-by: Marco Elver <elver@google.com>
+Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
+Link: https://lkml.kernel.org/r/20210527104711.2671610-1-elver@google.com
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ kernel/events/core.c |    2 ++
+ 1 file changed, 2 insertions(+)
+
+--- a/kernel/events/core.c
++++ b/kernel/events/core.c
+@@ -3497,7 +3497,9 @@ find_get_context(struct pmu *pmu, struct
+               cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
+               ctx = &cpuctx->ctx;
+               get_ctx(ctx);
++              raw_spin_lock_irqsave(&ctx->lock, flags);
+               ++ctx->pin_count;
++              raw_spin_unlock_irqrestore(&ctx->lock, flags);
+ 
+               return ctx;
+       }

diff --git a/queue-4.4/series b/queue-4.4/series
index 208d0e721a9698c2f57928e451ea98c20192f706..ec99373a0abf36a93360fbe8e879b39c4608a6e3 100644 (file)
--- a/queue-4.4/series
+++ b/queue-4.4/series
@@ -25,3 +25,4 @@ usb-serial-ftdi_sio-add-novatech-orionmx-product-id.patch
 usb-serial-omninet-add-device-id-for-zyxel-omni-56k-plus.patch
 usb-serial-quatech2-fix-control-request-directions.patch
 usb-gadget-eem-fix-wrong-eem-header-operation.patch
+perf-fix-data-race-between-pin_count-increment-decrement.patch