From: Marco Elver <elver@google.com>
To: elver@google.com, "Paul E. McKenney" <paulmck@kernel.org>
Cc: Alexander Potapenko <glider@google.com>,
Boqun Feng <boqun.feng@gmail.com>, Borislav Petkov <bp@alien8.de>,
Dmitry Vyukov <dvyukov@google.com>,
Ingo Molnar <mingo@kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Mark Rutland <mark.rutland@arm.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Waiman Long <longman@redhat.com>, Will Deacon <will@kernel.org>,
kasan-dev@googlegroups.com, linux-arch@vger.kernel.org,
linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org
Subject: [PATCH v2 03/23] kcsan: Avoid checking scoped accesses from nested contexts
Date: Thu, 18 Nov 2021 09:10:07 +0100 [thread overview]
Message-ID: <20211118081027.3175699-4-elver@google.com> (raw)
In-Reply-To: <20211118081027.3175699-1-elver@google.com>
Avoid checking scoped accesses from nested contexts (such as nested
interrupts or in scheduler code) which share the same kcsan_ctx.
This is to avoid detecting false positive races of accesses in the same
thread with currently scoped accesses: consider setting up a watchpoint
for a non-scoped (normal) access that also "conflicts" with a current
scoped access. In a nested interrupt (or in the scheduler), which shares
the same kcsan_ctx, we cannot check scoped accesses set up in the parent
context -- simply ignore them in this case.
With the introduction of kcsan_ctx::disable_scoped, we can also clean up
kcsan_check_scoped_accesses()'s recursion guard, and do not need to
modify the list's prev pointer.
Signed-off-by: Marco Elver <elver@google.com>
---
include/linux/kcsan.h | 1 +
kernel/kcsan/core.c | 18 +++++++++++++++---
2 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/include/linux/kcsan.h b/include/linux/kcsan.h
index fc266ecb2a4d..13cef3458fed 100644
--- a/include/linux/kcsan.h
+++ b/include/linux/kcsan.h
@@ -21,6 +21,7 @@
*/
struct kcsan_ctx {
int disable_count; /* disable counter */
+ int disable_scoped; /* disable scoped access counter */
int atomic_next; /* number of following atomic ops */
/*
diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index e34a1710b7bc..bd359f8ee63a 100644
--- a/kernel/kcsan/core.c
+++ b/kernel/kcsan/core.c
@@ -204,15 +204,17 @@ check_access(const volatile void *ptr, size_t size, int type, unsigned long ip);
static noinline void kcsan_check_scoped_accesses(void)
{
struct kcsan_ctx *ctx = get_ctx();
- struct list_head *prev_save = ctx->scoped_accesses.prev;
struct kcsan_scoped_access *scoped_access;
- ctx->scoped_accesses.prev = NULL; /* Avoid recursion. */
+ if (ctx->disable_scoped)
+ return;
+
+ ctx->disable_scoped++;
list_for_each_entry(scoped_access, &ctx->scoped_accesses, list) {
check_access(scoped_access->ptr, scoped_access->size,
scoped_access->type, scoped_access->ip);
}
- ctx->scoped_accesses.prev = prev_save;
+ ctx->disable_scoped--;
}
/* Rules for generic atomic accesses. Called from fast-path. */
@@ -465,6 +467,15 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned
goto out;
}
+ /*
+ * Avoid races of scoped accesses from nested interrupts (or scheduler).
+ * Assume setting up a watchpoint for a non-scoped (normal) access that
+ * also conflicts with a current scoped access. In a nested interrupt,
+ * which shares the context, it would check a conflicting scoped access.
+ * To avoid, disable scoped access checking.
+ */
+ ctx->disable_scoped++;
+
/*
* Save and restore the IRQ state trace touched by KCSAN, since KCSAN's
* runtime is entered for every memory access, and potentially useful
@@ -578,6 +589,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned
if (!kcsan_interrupt_watcher)
local_irq_restore(irq_flags);
kcsan_restore_irqtrace(current);
+ ctx->disable_scoped--;
out:
user_access_restore(ua_flags);
}
--
2.34.0.rc2.393.gf8c9666880-goog
next prev parent reply other threads:[~2021-11-18 8:11 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-18 8:10 [PATCH v2 00/23] kcsan: Support detecting a subset of missing memory barriers Marco Elver
2021-11-18 8:10 ` [PATCH v2 01/23] kcsan: Refactor reading of instrumented memory Marco Elver
2021-11-18 11:08 ` Mark Rutland
2021-11-18 8:10 ` [PATCH v2 02/23] kcsan: Remove redundant zero-initialization of globals Marco Elver
2021-11-18 11:09 ` Mark Rutland
2021-11-18 8:10 ` Marco Elver [this message]
2021-11-29 8:47 ` [PATCH v2 03/23] kcsan: Avoid checking scoped accesses from nested contexts Boqun Feng
2021-11-29 10:57 ` Marco Elver
2021-11-29 14:26 ` Boqun Feng
2021-11-29 14:42 ` Marco Elver
2021-11-18 8:10 ` [PATCH v2 04/23] kcsan: Add core support for a subset of weak memory modeling Marco Elver
2021-11-18 8:10 ` [PATCH v2 05/23] kcsan: Add core memory barrier instrumentation functions Marco Elver
2021-11-18 8:10 ` [PATCH v2 06/23] kcsan, kbuild: Add option for barrier instrumentation only Marco Elver
2021-11-18 8:10 ` [PATCH v2 07/23] kcsan: Call scoped accesses reordered in reports Marco Elver
2021-11-18 8:10 ` [PATCH v2 08/23] kcsan: Show location access was reordered to Marco Elver
2021-11-18 8:10 ` [PATCH v2 09/23] kcsan: Document modeling of weak memory Marco Elver
2021-11-18 8:10 ` [PATCH v2 10/23] kcsan: test: Match reordered or normal accesses Marco Elver
2021-11-18 8:10 ` [PATCH v2 11/23] kcsan: test: Add test cases for memory barrier instrumentation Marco Elver
2021-11-18 8:10 ` [PATCH v2 12/23] kcsan: Ignore GCC 11+ warnings about TSan runtime support Marco Elver
2021-11-18 8:10 ` [PATCH v2 13/23] kcsan: selftest: Add test case to check memory barrier instrumentation Marco Elver
2021-11-18 8:10 ` [PATCH v2 14/23] locking/barriers, kcsan: Add instrumentation for barriers Marco Elver
2021-11-18 8:10 ` [PATCH v2 15/23] locking/barriers, kcsan: Support generic instrumentation Marco Elver
2021-11-18 8:10 ` [PATCH v2 16/23] locking/atomics, kcsan: Add instrumentation for barriers Marco Elver
2021-11-18 8:10 ` [PATCH v2 17/23] asm-generic/bitops, " Marco Elver
2021-11-18 8:10 ` [PATCH v2 18/23] x86/barriers, kcsan: Use generic instrumentation for non-smp barriers Marco Elver
2021-11-18 8:10 ` [PATCH v2 19/23] x86/qspinlock, kcsan: Instrument barrier of pv_queued_spin_unlock() Marco Elver
2021-11-18 8:10 ` [PATCH v2 20/23] mm, kcsan: Enable barrier instrumentation Marco Elver
2021-11-18 8:10 ` [PATCH v2 21/23] sched, kcsan: Enable memory " Marco Elver
2021-11-18 8:10 ` [PATCH v2 22/23] objtool, kcsan: Add memory barrier instrumentation to whitelist Marco Elver
2021-11-18 8:10 ` [PATCH v2 23/23] objtool, kcsan: Remove memory barrier instrumentation from noinstr Marco Elver
2021-11-19 20:31 ` Josh Poimboeuf
2021-11-19 21:31 ` Marco Elver
2021-11-23 11:29 ` Marco Elver
2021-11-24 17:53 ` Josh Poimboeuf
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