Re: [PATCH] megaraid_sas: fix for 32bit apps

[Tomas Henzl <thenzl@redhat.com>]

On 02/10/2010 08:36 PM, James Bottomley wrote:
> On Fri, 2010-02-05 at 18:04 +0100, Tomas Henzl wrote:
>   
>> It looks like this patch -
>> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=7b2519afa1abd1b9f63aa1e90879307842422dae
>> has caused a problem for 32bit programs with 64bit os - 
>> http://bugzilla.kernel.org/show_bug.cgi?id=15001
>>
>> megaraid: convert user space 32bit pointer 
>> to a 64 bit one when needed.
>>
>> Signed-off-by: Tomas Henzl <thenzl@redhat.com>
>>
>> diff --git a/drivers/scsi/megaraid/megaraid_sas.c b/drivers/scsi/megaraid/megaraid_sas.c
>> index 708ea31..7617b8e 100644
>> --- a/drivers/scsi/megaraid/megaraid_sas.c
>> +++ b/drivers/scsi/megaraid/megaraid_sas.c
>> @@ -3781,6 +3781,8 @@ static int megasas_mgmt_compat_ioctl_fw(struct file *file, unsigned long arg)
>>  	    compat_alloc_user_space(sizeof(struct megasas_iocpacket));
>>  	int i;
>>  	int error = 0;
>> +	compat_uptr_t ptr;
>> +	u8 *sense_ptr;
>>  
>>  	if (clear_user(ioc, sizeof(*ioc)))
>>  		return -EFAULT;
>> @@ -3793,9 +3795,19 @@ static int megasas_mgmt_compat_ioctl_fw(struct file *file, unsigned long arg)
>>  	    copy_in_user(&ioc->sge_count, &cioc->sge_count, sizeof(u32)))
>>  		return -EFAULT;
>>  
>> -	for (i = 0; i < MAX_IOCTL_SGE; i++) {
>> -		compat_uptr_t ptr;
>> +	/*
>> +	 * The sense_ptr is used in megasas_mgmt_fw_ioctl only when
>> +	 * sense_len is not null, so prepare the 64bit value under
>> +	 * the same condition.
>> +	 */
>> +	if (ioc->sense_len) {
>> +		sense_ptr = ioc->frame.raw + ioc->sense_off;
>> +		if (get_user(ptr, (compat_uptr_t *)sense_ptr) ||
>> +		    put_user(ptr, (unsigned long *)sense_ptr))
>>     
> This should be put_user(compat_ptr(ptr) ...) to make sure we get proper
> warn free promotion.
>   
ok

> For symmetry, shouldn't we be reading from cioc?  I know technically the
> copy_in_user(ioc->frame.raw, cioc->frame.raw, 128) above did this, but
> it might look confusing to someone coming to the code for the first
> time.
>   
You are right, I just wanted to save some lines, but it could be confusing.

> To be honest, I also don't think ioc->frame.raw + ioc->sense_off is
> legal: it's dereferencing a userspace pointer (ioc->sense_off), which
> will fault on non-x86 boxes, but this isn't a criticism of the patch so
> much as the whole driver.
>
> Bo, this looks like a security fix, because userspace can cause
> arbitrary data scribble currently by stuffing carefully crafted values
> into the four bytes after the 32 bit sense pointer, so I'd like to apply
> it asap.
>
> Thanks,
>
> James
>   

New version, compile tested.

megaraid: convert user space 32bit pointer 
to a 64 bit one when needed.

Signed-off-by: Tomas Henzl <thenzl@redhat.com>

diff --git a/drivers/scsi/megaraid/megaraid_sas.c b/drivers/scsi/megaraid/megaraid_sas.c
index 708ea31..cb70224 100644
--- a/drivers/scsi/megaraid/megaraid_sas.c
+++ b/drivers/scsi/megaraid/megaraid_sas.c
@@ -3781,6 +3781,8 @@ static int megasas_mgmt_compat_ioctl_fw(struct file *file, unsigned long arg)
 	    compat_alloc_user_space(sizeof(struct megasas_iocpacket));
 	int i;
 	int error = 0;
+	compat_uptr_t ptr;
+	u8 *sense_cioc_ptr, *sense_ioc_ptr;
 
 	if (clear_user(ioc, sizeof(*ioc)))
 		return -EFAULT;
@@ -3793,9 +3795,20 @@ static int megasas_mgmt_compat_ioctl_fw(struct file *file, unsigned long arg)
 	    copy_in_user(&ioc->sge_count, &cioc->sge_count, sizeof(u32)))
 		return -EFAULT;
 
-	for (i = 0; i < MAX_IOCTL_SGE; i++) {
-		compat_uptr_t ptr;
+	/*
+	 * The sense_ptr is used in megasas_mgmt_fw_ioctl only when
+	 * sense_len is not null, so prepare the 64bit value under
+	 * the same condition.
+	 */
+	if (ioc->sense_len) {
+		sense_ioc_ptr = ioc->frame.raw + ioc->sense_off;
+		sense_cioc_ptr = cioc->frame.raw + cioc->sense_off;
+		if (get_user(ptr, (compat_uptr_t *)sense_cioc_ptr) ||
+		    put_user(compat_ptr(ptr), (unsigned long *)sense_ioc_ptr))
+			return -EFAULT;
+	}
 
+	for (i = 0; i < MAX_IOCTL_SGE; i++) {
 		if (get_user(ptr, &cioc->sgl[i].iov_base) ||
 		    put_user(compat_ptr(ptr), &ioc->sgl[i].iov_base) ||
 		    copy_in_user(&ioc->sgl[i].iov_len,