From: Mark Rutland <mark.rutland@arm.com>
To: Russell King - ARM Linux <linux@armlinux.org.uk>
Cc: "Thomas Garnier" <thgarnie@google.com>,
"David Howells" <dhowells@redhat.com>,
"Dave Hansen" <dave.hansen@intel.com>,
"Arnd Bergmann" <arnd@arndb.de>,
"Al Viro" <viro@zeniv.linux.org.uk>,
"René Nyffenegger" <mail@renenyffenegger.ch>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Kees Cook" <keescook@chromium.org>,
"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
"David S . Miller" <davem@davemloft.net>,
"Andy Lutomirski" <luto@kernel.org>,
"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
"Nicolas Pitre" <nicolas.pitre@linaro.org>,
"Petr Mladek" <pmladek@suse.com>,
"Sebastian Andrzej Siewior" <bigeasy@linutronix.de>,
"Sergey Senozhatsky" <sergey.senozhatsky@gmail.com>,
"Helge Deller" <deller@gmx.de>, "Rik van Riel" <riel@redhat.com>,
"Ingo Molnar" <mingo@kernel.org>,
"Oleg Nesterov" <oleg@redhat.com>,
"John Stultz" <john.stultz@linaro.org>,
"Thomas Gleixner" <tglx@linutronix.de>
Subject: Re: [PATCH v2 1/4] syscalls: Restore address limit after a syscall
Date: Thu, 9 Mar 2017 15:21:45 +0000 [thread overview]
Message-ID: <20170309152144.GA11966@leverpostej> (raw)
In-Reply-To: <20170309134456.GI21222@n2100.armlinux.org.uk>
On Thu, Mar 09, 2017 at 01:44:56PM +0000, Russell King - ARM Linux wrote:
> On Thu, Mar 09, 2017 at 12:09:55PM +0000, Mark Rutland wrote:
> > On Wed, Mar 08, 2017 at 05:24:53PM -0800, Thomas Garnier wrote:
> > It would be simpler to wrap the call entirely, e.g. have:
> >
> > #ifdef CONFIG_WHATEVER
> > static inline void verify_pre_usermode_state(void)
> > {
> > if (segment_eq(get_fs(), USER_DS))
> > __verify_pre_usermode_state();
> > }
> > #else
> > static inline void verify_pre_usermode_state(void) { }
> > #endif
>
> That's utterly pointless - you've missed a detail.
>
> > > @@ -199,7 +215,10 @@ extern struct trace_event_functions exit_syscall_print_funcs;
> > > asmlinkage long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
> > > asmlinkage long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
> > > { \
> > > + bool user_caller = has_user_ds(); \
> > > long ret = SYSC##name(__MAP(x,__SC_CAST,__VA_ARGS__)); \
> > > + if (user_caller) \
> > > + verify_pre_usermode_state(); \
> >
> > ... then we can unconditionally use verify_pre_usermode_state() here ...
>
> Look at this closely. has_user_ds() is called _before_ the syscall code
> is invoked. It's checking what conditions the syscall was entered from.
> If the syscall was entered with the user segment selected, then we run
> a check on the system state _after_ the syscall code has returned.
Indeed; I clearly did not consider this correctly.
Sorry for the noise.
Thanks,
Mark.
next prev parent reply other threads:[~2017-03-09 15:21 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-09 1:24 [PATCH v2 1/4] syscalls: Restore address limit after a syscall Thomas Garnier
2017-03-09 1:24 ` [PATCH v2 2/4] x86/syscalls: Specific usage of verify_pre_usermode_state Thomas Garnier
2017-03-09 1:24 ` [PATCH v2 3/4] arm/syscalls: " Thomas Garnier
2017-03-09 1:24 ` [PATCH v2 4/4] arm64/syscalls: " Thomas Garnier
2017-03-09 12:23 ` Mark Rutland
2017-03-09 15:56 ` Thomas Garnier
2017-03-09 16:05 ` Mark Rutland
2017-03-09 16:19 ` Thomas Garnier
2017-03-09 16:26 ` Russell King - ARM Linux
2017-03-09 16:35 ` Thomas Garnier
2017-03-09 17:05 ` Russell King - ARM Linux
2017-03-09 8:42 ` [PATCH v2 1/4] syscalls: Restore address limit after a syscall Borislav Petkov
2017-03-09 15:48 ` Thomas Garnier
2017-03-09 17:27 ` Andy Lutomirski
2017-03-09 17:41 ` Thomas Garnier
2017-03-09 10:39 ` Sergey Senozhatsky
2017-03-09 12:09 ` Mark Rutland
2017-03-09 13:44 ` Russell King - ARM Linux
2017-03-09 15:21 ` Mark Rutland [this message]
2017-03-09 15:54 ` Thomas Garnier
2017-03-09 15:52 ` Thomas Garnier
2017-03-09 12:32 ` Christian Borntraeger
2017-03-09 15:53 ` Thomas Garnier
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