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From: David Laight <David.Laight@ACULAB.COM>
To: 'Al Viro' <viro@zeniv.linux.org.uk>, Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"x86@kernel.org" <x86@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"Borislav Petkov" <bp@alien8.de>
Subject: RE: [RFC][PATCH 01/22] x86 user stack frame reads: switch to explicit __get_user()
Date: Mon, 30 Mar 2020 15:54:22 +0000	[thread overview]
Message-ID: <0c08c4e00e4e4965969a16410e4e15d1@AcuMS.aculab.com> (raw)
In-Reply-To: <20200329175735.GC23230@ZenIV.linux.org.uk>

From: Al Viro
> Sent: 29 March 2020 18:58
...
> [*] IMO compat_alloc_user_space() should die; this "grab some space on
> user stack, copy the 32bit data structure into 64bit equivalent there,
> complete with pointer chasing and creating 64bit equivalents of everything
> that's referenced from that struct, then call native ioctl, then do the
> reverse conversion" is just plain wrong.  That native ioctl is going to
> bring the structures we'd constructed back into the kernel space and
> work with them there; we might as well separate the function that work
> with the copied struct (usually we do have those anyway) and call those
> instead the native ioctl.  And skip the damn "copy the structures we'd
> built into temp allocation on user stack, then have it copied back"
> part.  We have relatively few callers, thankfully.

I helped rip the same 'stackgap' code out of netbsd many years ago.
No only was it being used for system call compatibility, but
also for security checks and rewriting filenames.
Completely hopeless in a threaded program.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)


  reply	other threads:[~2020-03-30 15:54 UTC|newest]

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-23 18:36 [RFC][PATCHSET] x86 uaccess cleanups Al Viro
2020-03-23 18:37 ` [RFC][PATCH 01/22] x86 user stack frame reads: switch to explicit __get_user() Al Viro
2020-03-23 18:37   ` [RFC][PATCH 02/22] x86 kvm page table walks: " Al Viro
2020-03-23 18:38   ` [RFC][PATCH 03/22] x86: switch sigframe sigset handling to explict __get_user()/__put_user() Al Viro
2020-03-23 18:38   ` [RFC][PATCH 04/22] x86: get rid of small constant size cases in raw_copy_{to,from}_user() Al Viro
2020-03-23 18:38   ` [RFC][PATCH 05/22] vm86: get rid of get_user_ex() use Al Viro
2020-03-23 18:38   ` [RFC][PATCH 06/22] x86: get rid of get_user_ex() in ia32_restore_sigcontext() Al Viro
2020-03-23 18:38   ` [RFC][PATCH 07/22] x86: get rid of get_user_ex() in restore_sigcontext() Al Viro
2020-03-23 18:38   ` [RFC][PATCH 08/22] x86: kill get_user_{try,catch,ex} Al Viro
2020-03-23 18:38   ` [RFC][PATCH 09/22] x86: switch save_v86_state() to unsafe_put_user() Al Viro
2020-03-23 18:38   ` [RFC][PATCH 10/22] x86: switch setup_sigcontext() " Al Viro
2020-03-23 18:38   ` [RFC][PATCH 11/22] x86: switch ia32_setup_sigcontext() " Al Viro
2020-03-23 18:38   ` [RFC][PATCH 12/22] x86: get rid of put_user_try in {ia32,x32}_setup_rt_frame() Al Viro
2020-03-23 18:38   ` [RFC][PATCH 13/22] x86: ia32_setup_sigcontext(): lift user_access_{begin,end}() into the callers Al Viro
2020-03-23 18:53     ` Linus Torvalds
2020-03-23 21:42       ` Al Viro
2020-03-23 18:38   ` [RFC][PATCH 14/22] x86: ia32_setup_frame(): consolidate uaccess areas Al Viro
2020-03-23 18:38   ` [RFC][PATCH 15/22] x86: ia32_setup_rt_frame(): " Al Viro
2020-03-23 18:38   ` [RFC][PATCH 16/22] x86: get rid of put_user_try in __setup_rt_frame() (both 32bit and 64bit) Al Viro
2020-03-23 18:38   ` [RFC][PATCH 17/22] x86: setup_sigcontext(): list user_access_{begin,end}() into callers Al Viro
2020-03-23 18:56     ` Linus Torvalds
2020-03-23 18:38   ` [RFC][PATCH 18/22] x86: __setup_frame(): consolidate uaccess areas Al Viro
2020-03-23 18:38   ` [RFC][PATCH 19/22] x86: __setup_rt_frame(): " Al Viro
2020-03-23 18:38   ` [RFC][PATCH 20/22] x86: x32_setup_rt_frame(): " Al Viro
2020-03-23 18:38   ` [RFC][PATCH 21/22] x86: unsafe_put_... macros for sigcontext and sigmask Al Viro
2020-03-23 18:38   ` [RFC][PATCH 22/22] kill uaccess_try() Al Viro
2020-03-24 15:15   ` [RFC][PATCH 01/22] x86 user stack frame reads: switch to explicit __get_user() Peter Zijlstra
2020-03-28 10:48   ` Ingo Molnar
2020-03-28 11:59     ` Al Viro
2020-03-29  9:26       ` Ingo Molnar
2020-03-29 16:50         ` Andy Lutomirski
2020-03-29 17:05           ` Linus Torvalds
2020-03-29 17:41           ` David Laight
2020-03-29 17:56             ` Linus Torvalds
2020-03-29 18:03               ` David Laight
2020-03-29 18:16                 ` Linus Torvalds
2020-03-29 18:32                   ` David Laight
2020-03-29 18:55                     ` Linus Torvalds
2020-03-29 21:21                   ` Andy Lutomirski
2020-03-29 22:06                     ` Linus Torvalds
2020-03-29 22:12                       ` Linus Torvalds
2020-03-29 18:16               ` Al Viro
2020-03-29 18:19                 ` Linus Torvalds
2020-03-29 17:57         ` Al Viro
2020-03-30 15:54           ` David Laight [this message]
2020-03-23 19:16 ` [RFC][PATCHSET] x86 uaccess cleanups Linus Torvalds
2020-03-27  2:24 ` [RFC][PATCHSET v2] " Al Viro
2020-03-27  2:26   ` Al Viro
2020-03-27  2:30     ` Al Viro
2020-03-27  2:31       ` [RFC][PATCH v2 01/22] x86 user stack frame reads: switch to explicit __get_user() Al Viro
2020-03-27  2:31         ` [RFC][PATCH v2 02/22] x86 kvm page table walks: " Al Viro
2020-03-27  2:31         ` [RFC][PATCH v2 03/22] x86: switch sigframe sigset handling to explict __get_user()/__put_user() Al Viro
2020-03-27  2:31         ` [RFC][PATCH v2 04/22] x86: get rid of small constant size cases in raw_copy_{to,from}_user() Al Viro
2020-03-27  2:31         ` [RFC][PATCH v2 05/22] vm86: get rid of get_user_ex() use Al Viro
2020-03-27  2:31         ` [RFC][PATCH v2 06/22] x86: get rid of get_user_ex() in ia32_restore_sigcontext() Al Viro
2020-03-27  2:31         ` [RFC][PATCH v2 07/22] x86: get rid of get_user_ex() in restore_sigcontext() Al Viro
2020-03-27  2:31         ` [RFC][PATCH v2 08/22] x86: kill get_user_{try,catch,ex} Al Viro
2020-03-27  2:31         ` [RFC][PATCH v2 09/22] x86: switch save_v86_state() to unsafe_put_user() Al Viro
2020-03-27  2:31         ` [RFC][PATCH v2 10/22] x86: switch setup_sigcontext() " Al Viro
2020-03-27  2:31         ` [RFC][PATCH v2 11/22] x86: switch ia32_setup_sigcontext() " Al Viro
2020-03-27  2:31         ` [RFC][PATCH v2 12/22] x86: get rid of put_user_try in {ia32,x32}_setup_rt_frame() Al Viro
2020-03-27  2:31         ` [RFC][PATCH v2 13/22] x86: ia32_setup_sigcontext(): lift user_access_{begin,end}() into the callers Al Viro
2020-03-27  2:31         ` [RFC][PATCH v2 14/22] x86: ia32_setup_frame(): consolidate uaccess areas Al Viro
2020-03-27  2:31         ` [RFC][PATCH v2 15/22] x86: ia32_setup_rt_frame(): " Al Viro
2020-03-27  2:31         ` [RFC][PATCH v2 16/22] x86: get rid of put_user_try in __setup_rt_frame() (both 32bit and 64bit) Al Viro
2020-03-27  2:32         ` [RFC][PATCH v2 17/22] x86: setup_sigcontext(): list user_access_{begin,end}() into callers Al Viro
2020-03-27  2:32         ` [RFC][PATCH v2 18/22] x86: __setup_frame(): consolidate uaccess areas Al Viro
2020-03-27  2:32         ` [RFC][PATCH v2 19/22] x86: __setup_rt_frame(): " Al Viro
2020-03-27  2:32         ` [RFC][PATCH v2 20/22] x86: x32_setup_rt_frame(): " Al Viro
2020-03-27  2:32         ` [RFC][PATCH v2 21/22] x86: unsafe_put-style macro for sigmask Al Viro
2020-03-27  2:32         ` [RFC][PATCH v2 22/22] kill uaccess_try() Al Viro

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