linux-kernel - Re: module: Fix regression introduced by commit: b0d7290e85a5 "module: clean up RO/NX handling."

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Message-ID: <20160126093951.1d6c80fe@ipc1.ka-ro>
Date:	Tue, 26 Jan 2016 09:39:51 +0100
From:	Lothar Waßmann <LW@...O-electronics.de>
To:	Brian Norris <computersforpeace@...il.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>, linux-kernel@...r.kernel.org
Subject: Re: module: Fix regression introduced by commit: b0d7290e85a5
 "module: clean up RO/NX handling."

Hi,

On Mon, 25 Jan 2016 15:41:08 -0800 Brian Norris wrote:
> On Mon, Jan 25, 2016 at 12:11:51PM +0100, Lothar Wassmann wrote:
> > commit b0d7290e85a5 ("module: clean up RO/NX handling.")
> > threw away the size checks which were in place before calling the
> > set_memory_*() functions.
> > This produces a kernel bug upon module load with
> > CONFIG_DEBUG_SET_MODULE_RONX=y:
> > 
> > kernel BUG at mm/memory.c:1898!
> > Internal error: Oops - BUG: 0 [#1] ARM
> > Modules linked in:
> > CPU: 0 PID: 825 Comm: modprobe Not tainted 4.4.0-next-20160121+ #53
> > Hardware name: Freescale MXS (Device Tree)
> > task: cef6c380 ti: ce93a000 task.ti: ce93a000
> > PC is at apply_to_page_range+0x190/0x1bc
> > LR is at change_memory_common+0x74/0xcc
> > pc : [<c0082d80>]    lr : [<c0011ce0>]    psr: 60000013
> > sp : ce93be40  ip : bf011000  fp : bf012000
> > r10: bf012000  r9 : bf0091d4  r8 : ce93be80
> > r7 : 00000000  r6 : bf012000  r5 : 00000001  r4 : bf012000
> > r3 : c0011d38  r2 : 00000000  r1 : bf012000  r0 : c0633458
> > Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
> > Control: 0005317f  Table: 4ef0c000  DAC: 00000051
> > Process modprobe (pid: 825, stack limit = 0xce93a190)
> > Stack: (0xce93be40 to 0xce93c000)
> > be40: c0633458 bf012000 00000000 bf012000 00000001 bf012000 00000000 00000080
> > be60: bf0091d4 ce93bef4 00000000 c0011ce0 ce93be80 00000000 bf0071dc bf0091e4
> > be80: 00000080 00000000 bf009100 ce93bf48 00000001 bf00910c bf009100 00000000
> > bea0: bf0091d4 c005d2a0 00000000 cfbd8de0 00000000 00000014 007fb980 00000000
> > bec0: d0a1d01c bf009250 bf00910c 00000000 d0a19000 b6e4b000 00000f80 755f6f74
> > bee0: 5f726573 bf007024 00000032 bf0071b4 00000006 00000000 00000000 00000000
> > bf00: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> > bf20: c005da70 0000306c 00000000 b6e4f06c d0a1d06c ce93a000 007fb980 00000051
> > bf40: 007fbbd8 c005dae0 d0a0a000 0001306c d0a1c98c d0a13c07 d0a177c8 0000a000
> > bf60: 0000cbe0 00000000 00000000 00000000 0000002a 0000002b 00000020 00000024
> > bf80: 00000018 00000000 b6f83228 bec859f8 00000000 00000080 c000a4e4 ce93a000
> > bfa0: 00000000 c000a340 b6f83228 bec859f8 b6e3c000 0001306c 007fb980 00000000
> > bfc0: b6f83228 bec859f8 00000000 00000080 007fb980 00000008 00000000 007fbbd8
> > bfe0: b6f1fa70 bec856c8 0000aab4 b6f1fa80 60000010 b6e3c000 00000000 00000000
> > [<c0082d80>] (apply_to_page_range) from [<c0011ce0>] (change_memory_common+0x74/0xcc)
> > [<c0011ce0>] (change_memory_common) from [<c005d2a0>] (load_module+0x16c8/0x1e3c)
> > [<c005d2a0>] (load_module) from [<c005dae0>] (SyS_init_module+0xcc/0x138)
> > [<c005dae0>] (SyS_init_module) from [<c000a340>] (ret_fast_syscall+0x0/0x38)
> > Code: e0834104 eaffffc3 e5191008 eaffffbb (e7f001f2)
> > ---[ end trace fbf287e335e94b28 ]---
> > 
> > This happens because the set_memory_*() functions are eventually being
> > called with a zero <size> parameter and thus apply_to_page_range() in
> > mm/memory.c barfs due to:
> > 	unsigned long end = addr + size;
> > ...
> > 	BUG_ON(addr >= end);
> 
> Hit this BUG_ON() on a mt8173 platform with v4.5-rc1.
> 
I just found a patch that fixes this problem in a different way (making
the set_memory_*() functions accept a zero size argument):
<1453561543-14756-1-git-send-email-mika.penttila@...tfour.com>
http://lkml.iu.edu/hypermail/linux/kernel/1601.2/04934.html

So this patch is obsolete.


Lothar Waßmann