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From: Masami Hiramatsu <mhiramat@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Shuah Khan <shuah@kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>
Cc: mhiramat@kernel.org, linux-kernel@vger.kernel.org,
	Andy Lutomirski <luto@amacapital.net>,
	Ingo Molnar <mingo@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Changbin Du <changbin.du@gmail.com>, Jann Horn <jannh@google.com>,
	Kees Cook <keescook@chromium.org>,
	Andy Lutomirski <luto@kernel.org>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Nadav Amit <namit@vmware.com>,
	Joel Fernandes <joel@joelfernandes.org>,
	yhs@fb.com
Subject: [RFC PATCH v6 1/6] x86/uaccess: Allow access_ok() in irq context if pagefault_disabled
Date: Mon, 18 Mar 2019 15:43:17 +0900	[thread overview]
Message-ID: <155289139725.7218.17265500814527931961.stgit@devnote2> (raw)
In-Reply-To: <155289137555.7218.9282784065958321058.stgit@devnote2>

WARN_ON_IN_IRQ() assumes that the access_ok() and following
user memory access can sleep. But this assumption is not
always correct; when the pagefault is disabled, following
memory access will just returns -EFAULT and never sleep.

Add pagefault_disabled() check in WARN_ON_ONCE() so that
it can ignore the case we call it with disabling pagefault.
For this purpose, this modified pagefault_disabled() as
an inline function.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 arch/x86/include/asm/uaccess.h |    4 +++-
 include/linux/uaccess.h        |    5 ++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 1954dd5552a2..11581dc098d5 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -66,7 +66,9 @@ static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, un
 })
 
 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
-# define WARN_ON_IN_IRQ()	WARN_ON_ONCE(!in_task())
+static inline bool pagefault_disabled(void);
+# define WARN_ON_IN_IRQ()	\
+	WARN_ON_ONCE(!in_task() && !pagefault_disabled())
 #else
 # define WARN_ON_IN_IRQ()
 #endif
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 37b226e8df13..ef3032db1aef 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -203,7 +203,10 @@ static inline void pagefault_enable(void)
 /*
  * Is the pagefault handler disabled? If so, user access methods will not sleep.
  */
-#define pagefault_disabled() (current->pagefault_disabled != 0)
+static inline bool pagefault_disabled(void)
+{
+	return current->pagefault_disabled != 0;
+}
 
 /*
  * The pagefault handler is in general disabled by pagefault_disable() or


  reply	other threads:[~2019-03-18  6:43 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-18  6:42 [RFC PATCH v6 0/6] tracing/probes: uaccess: Add support user-space access Masami Hiramatsu
2019-03-18  6:43 ` Masami Hiramatsu [this message]
2019-03-22  2:46   ` [RFC PATCH v6 1/6] x86/uaccess: Allow access_ok() in irq context if pagefault_disabled Steven Rostedt
2019-05-06 15:22     ` Masami Hiramatsu
2019-05-06 15:39       ` Steven Rostedt
2019-03-18  6:43 ` [RFC PATCH v6 2/6] uaccess: Add non-pagefault user-space read functions Masami Hiramatsu
2019-03-18  6:43 ` [RFC PATCH v6 3/6] tracing/probe: Add ustring type for user-space string Masami Hiramatsu
2019-03-18  6:43 ` [RFC PATCH v6 4/6] tracing/probe: Support user-space dereference Masami Hiramatsu
2019-05-06 15:52   ` Steven Rostedt
2019-05-08  4:11     ` Masami Hiramatsu
2019-05-08 15:22       ` Steven Rostedt
2019-05-13 12:11         ` Masami Hiramatsu
2019-03-18  6:44 ` [RFC PATCH v6 5/6] selftests/ftrace: Add user-memory access syntax testcase Masami Hiramatsu
2019-03-18  6:44 ` [RFC PATCH v6 6/6] perf-probe: Add user memory access attribute support Masami Hiramatsu

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