From: Masami Hiramatsu <mhiramat@kernel.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
kernel test robot <lkp@intel.com>,
Steven Rostedt <rostedt@goodmis.org>,
Shuah Khan <shuah@kernel.org>,
Linux List Kernel Mailing <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, lkp@01.org
Subject: Re: [uaccess] 780464aed0: WARNING:at_arch/x86/include/asm/uaccess.h:#strnlen_user/0x
Date: Tue, 5 Mar 2019 18:01:26 +0900 [thread overview]
Message-ID: <20190305180126.0f7201d8ec733fdc887135f1@kernel.org> (raw)
In-Reply-To: <20190305172241.2eef39c6ca74d09120bbbcad@kernel.org>
On Tue, 5 Mar 2019 17:22:41 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:
> On Tue, 5 Mar 2019 11:36:35 +0900
> Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> > On Mon, 4 Mar 2019 10:59:22 -0800
> > Linus Torvalds <torvalds@linux-foundation.org> wrote:
> >
> > I think the better way to do this is allowing strncpy_from_user()
> > if some conditions are match, like
> >
> > - strncpy_from_user() will be able to copy user memory with set_fs(USER_DS)
> > - strncpy_from_user() can copy kernel memory with set_fs(KERNEL_DS)
> > - strncpy_from_user() can access unsafe memory in IRQ context if
> > pagefault is disabled.
> >
> > This is almost done, except for CONFIG_DEBUG_ATOMIC_SLEEP=y on x86.
> >
> > So, what about adding a condition to WARN_ON_IN_IRQ() like below
> > instead of introducing user_access_ok() ?
OK, here is the patch. Does it work for us?
====
x86/uaccess: Verify access_ok() context strictly
From: Masami Hiramatsu <mhiramat@kernel.org>
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 780f2b4..b98a552 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -70,7 +70,9 @@ 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 37b226e..ef3032d 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
next prev parent reply other threads:[~2019-03-05 9:01 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-28 16:02 [PATCH v5 0/6] tracing/probes: uaccess: Add support user-space access Masami Hiramatsu
2019-02-28 16:02 ` [PATCH v5 1/6] uaccess: Add user_access_ok() Masami Hiramatsu
2019-02-28 16:03 ` [PATCH v5 2/6] uaccess: Use user_access_ok() in user_access_begin() Masami Hiramatsu
2019-03-03 17:39 ` [uaccess] 780464aed0: WARNING:at_arch/x86/include/asm/uaccess.h:#strnlen_user/0x kernel test robot
2019-03-03 19:53 ` Linus Torvalds
2019-03-04 1:14 ` Masami Hiramatsu
2019-03-04 2:37 ` Linus Torvalds
2019-03-04 9:06 ` Masami Hiramatsu
2019-03-04 15:16 ` Masami Hiramatsu
2019-03-04 15:58 ` Jann Horn
2019-03-04 18:59 ` Linus Torvalds
2019-03-05 2:36 ` Masami Hiramatsu
2019-03-05 8:22 ` Masami Hiramatsu
2019-03-05 9:01 ` Masami Hiramatsu [this message]
2019-03-05 9:07 ` Peter Zijlstra
2019-03-05 13:58 ` Masami Hiramatsu
2019-03-05 14:53 ` Peter Zijlstra
2019-03-05 15:18 ` Masami Hiramatsu
2019-03-04 3:20 ` [LKP] " Rong Chen
2019-02-28 16:03 ` [PATCH v5 3/6] uaccess: Add non-pagefault user-space read functions Masami Hiramatsu
2019-02-28 22:49 ` Yonghong Song
2019-03-01 2:29 ` Masami Hiramatsu
2019-03-01 6:30 ` Yonghong Song
2019-02-28 16:04 ` [PATCH v5 4/6] tracing/probe: Add ustring type for user-space string Masami Hiramatsu
2019-02-28 16:04 ` [PATCH v5 5/6] tracing/probe: Support user-space dereference Masami Hiramatsu
2019-02-28 16:05 ` [PATCH v5 6/6] selftests/ftrace: Add user-memory access syntax testcase Masami Hiramatsu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190305180126.0f7201d8ec733fdc887135f1@kernel.org \
--to=mhiramat@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=alexei.starovoitov@gmail.com \
--cc=changbin.du@gmail.com \
--cc=jannh@google.com \
--cc=joel@joelfernandes.org \
--cc=keescook@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lkp@01.org \
--cc=lkp@intel.com \
--cc=luto@amacapital.net \
--cc=luto@kernel.org \
--cc=mingo@kernel.org \
--cc=namit@vmware.com \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=shuah@kernel.org \
--cc=torvalds@linux-foundation.org \
--cc=yhs@fb.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).