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From: Randy Dunlap <rdunlap@infradead.org>
To: Steve French <smfrench@gmail.com>,
	CIFS <linux-cifs@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	LAK <linux-arm-kernel@lists.infradead.org>
Subject: Re: Fwd: [EXTERNAL] Re: ioctl.c:undefined reference to `__get_user_bad'
Date: Mon, 17 May 2021 14:06:33 -0700	[thread overview]
Message-ID: <5b29fe73-7c95-0b9f-3154-c053fa94cb67@infradead.org> (raw)
In-Reply-To: <d3e24342-4f30-6a2f-3617-a917539eac94@infradead.org>

[adding back linux-arm-kernel; what happened to it? ]


On 5/17/21 2:04 PM, Randy Dunlap wrote:
> On 5/17/21 10:13 AM, Steve French wrote:
>>> If you fix the issue, kindly add following tag as appropriate
>>> Reported-by: kernel test robot <lkp@intel.com>
>>>
>>> All errors (new ones prefixed by >>):
>>>
>>>    arm-linux-gnueabi-ld: fs/cifs/ioctl.o: in function `cifs_dump_full_key':
>>>>> ioctl.c:(.text+0x44): undefined reference to `__get_user_bad'
>>>
>>
>> <snip>
>>
>>> # CONFIG_MMU is not set
>>>
>>> and arch/arm/include/asm/uaccess.h does not implement get_user(size 8 bytes)
>>> for the non-MMU case:
>>
>> I see another place in fs/cifs/ioctl.c where we already had been doing
>> a get_user() into a u64 - any idea what you are supposed to do
>> instead?  Any example code where people have worked around this.
> 
> Hi Steve,
> 
> This change in cifs_dump_full_key() makes it build OK:
> 
> -       if (get_user(suid, (__u64 __user *)arg))
> +       if (get_user(suid, (unsigned int __user *)arg))
> 
> 
> That is what the other call uses:
> 
> 		case FS_IOC_SETFLAGS:
> 			cifs_dbg(VFS, "cifs ioctl FS_IOC_SETFLAGS:\n");
> 			if (pSMBFile == NULL)
> 				break;
> 			tcon = tlink_tcon(pSMBFile->tlink);
> 			caps = le64_to_cpu(tcon->fsUnixInfo.Capability);
> 
> 			if (get_user(ExtAttrBits, (int __user *)arg)) {
> 				rc = -EFAULT;
> 				break;
> 			}
> 
> However, my reading/understanding is that the one immediately above
> is incorrect, as is the -/+ patch above it, since get_user() gets its
> data size (1, 2, 4, 8) from the type of the pointer that is passed to it.
> For 8 bytes (64 bits), 'int' is not sufficient, so IMO the get_user()
> call that builds:
> 			if (get_user(ExtAttrBits, (int __user *)arg)) {
> is a bug. It should be:
> 			if (get_user(ExtAttrBits, (__u64 __user *)arg)) {
> and if I make that latter change in the source file, the build says:
> 
> arm-linux-gnueabi-ld: fs/cifs/ioctl.o: in function `cifs_dump_full_key':
> ioctl.c:(.text+0x14): undefined reference to `__get_user_bad'
> arm-linux-gnueabi-ld: fs/cifs/ioctl.o: in function `cifs_ioctl':
> ioctl.c:(.text+0x1f2): undefined reference to `__get_user_bad'
> 
> so now both of them fail on the get_user() of 8 bytes.
> 
> Hope that clarifies things.  It tells me that arm no-MMU still
> needs support for get_user() of size 8 bytes.
> 

-- 
~Randy


  reply	other threads:[~2021-05-17 21:06 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <202105110829.MHq04tJz-lkp@intel.com>
     [not found] ` <a022694d-426a-0415-83de-4cc5cd9d1d38@infradead.org>
     [not found]   ` <MN2PR21MB15184963469FEC9B13433964E42D9@MN2PR21MB1518.namprd21.prod.outlook.com>
2021-05-17 17:13     ` Steve French
2021-05-17 21:04       ` Randy Dunlap
2021-05-17 21:06         ` Randy Dunlap [this message]
2021-05-18 10:03           ` Russell King (Oracle)
2021-05-19  1:48             ` Randy Dunlap
2021-05-19  9:11         ` Aurélien Aptel

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