From: Peter Zijlstra <peterz@infradead.org>
To: lkp@lists.01.org
Subject: Re: [uaccess] 780464aed0: WARNING:at_arch/x86/include/asm/uaccess.h:#strnlen_user/0x
Date: Tue, 05 Mar 2019 15:53:06 +0100 [thread overview]
Message-ID: <20190305145306.GL32477@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190305225801.a63ac8712105ab2e673be1bc@kernel.org>
[-- Attachment #1: Type: text/plain, Size: 887 bytes --]
On Tue, Mar 05, 2019 at 10:58:01PM +0900, Masami Hiramatsu wrote:
> Could you tell me why WARN_ON_ONCE(!in_task()) is needed in access_ok()?
That came from here:
lkml.kernel.org/r/20190225145240.GB32534(a)hirez.programming.kicks-ass.net
Because in-irq usage is dodgy, since we don't actually know what mm or
ds it loaded.
> > I dislike that whole KERNEL_DS thing, but obviously that's not something
> > that's going away.
> >
> > Would something like:
> >
> > WARN_ON_ONCE(!(in_task || segment_eq(get_fs(), USER_DS)))
> >
> > Work? Then we allow KERNEL_DS in task context, but for interrupt and
> > others require USER_DS.
>
> But what would this mean? I can't understand why we limit using
> access_ok() so strictly and narrow the cases.
Because it's been a source of bugs. Any sanity checking we can put in
seems like a good thing at this point.
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Masami Hiramatsu <mhiramat@kernel.org>,
g@hirez.programming.kicks-ass.net
Cc: Linus Torvalds <torvalds@linux-foundation.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 15:53:06 +0100 [thread overview]
Message-ID: <20190305145306.GL32477@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190305225801.a63ac8712105ab2e673be1bc@kernel.org>
On Tue, Mar 05, 2019 at 10:58:01PM +0900, Masami Hiramatsu wrote:
> Could you tell me why WARN_ON_ONCE(!in_task()) is needed in access_ok()?
That came from here:
lkml.kernel.org/r/20190225145240.GB32534@hirez.programming.kicks-ass.net
Because in-irq usage is dodgy, since we don't actually know what mm or
ds it loaded.
> > I dislike that whole KERNEL_DS thing, but obviously that's not something
> > that's going away.
> >
> > Would something like:
> >
> > WARN_ON_ONCE(!(in_task || segment_eq(get_fs(), USER_DS)))
> >
> > Work? Then we allow KERNEL_DS in task context, but for interrupt and
> > others require USER_DS.
>
> But what would this mean? I can't understand why we limit using
> access_ok() so strictly and narrow the cases.
Because it's been a source of bugs. Any sanity checking we can put in
seems like a good thing at this point.
next prev parent reply other threads:[~2019-03-05 14:53 UTC|newest]
Thread overview: 42+ 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 17:39 ` kernel test robot
2019-03-03 19:53 ` Linus Torvalds
2019-03-03 19:53 ` Linus Torvalds
2019-03-04 1:14 ` Masami Hiramatsu
2019-03-04 1:14 ` Masami Hiramatsu
2019-03-04 2:37 ` Linus Torvalds
2019-03-04 2:37 ` Linus Torvalds
2019-03-04 9:06 ` Masami Hiramatsu
2019-03-04 9:06 ` Masami Hiramatsu
2019-03-04 15:16 ` Masami Hiramatsu
2019-03-04 15:16 ` Masami Hiramatsu
2019-03-04 15:58 ` Jann Horn
2019-03-04 15:58 ` Jann Horn
2019-03-04 18:59 ` Linus Torvalds
2019-03-04 18:59 ` Linus Torvalds
2019-03-05 2:36 ` Masami Hiramatsu
2019-03-05 2:36 ` Masami Hiramatsu
2019-03-05 8:22 ` Masami Hiramatsu
2019-03-05 8:22 ` Masami Hiramatsu
2019-03-05 9:01 ` Masami Hiramatsu
2019-03-05 9:01 ` Masami Hiramatsu
2019-03-05 9:07 ` Peter Zijlstra
2019-03-05 9:07 ` Peter Zijlstra
2019-03-05 13:58 ` Masami Hiramatsu
2019-03-05 13:58 ` Masami Hiramatsu
2019-03-05 14:53 ` Peter Zijlstra [this message]
2019-03-05 14:53 ` Peter Zijlstra
2019-03-05 15:18 ` Masami Hiramatsu
2019-03-05 15:18 ` Masami Hiramatsu
2019-03-04 3:20 ` Rong Chen
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
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