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[PATCH] block: floppy: fix uninitialized use of outparam in fd_locked_ioctl

Purva Yeshi posted 1 patch 3 months ago 
drivers/block/floppy.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
[PATCH] block: floppy: fix uninitialized use of outparam in fd_locked_ioctl
Posted by Purva Yeshi 3 months ago 
Fix Smatch-detected error:
drivers/block/floppy.c:3569 fd_locked_ioctl() error:
uninitialized symbol 'outparam'.

Use the outparam pointer only after it is explicitly initialized.
Previously, fd_copyout() was called unconditionally after the switch-case
statement, assuming outparam would always be set when _IOC_READ was active.
However, not all paths ensured this, which led to potential use of an
uninitialized pointer.

Move fd_copyout() calls directly into the relevant case blocks immediately
after outparam is set. This ensures it is only called when safe and
applicable.

Signed-off-by: Purva Yeshi <purvayeshi550@gmail.com>
---
 drivers/block/floppy.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index e97432032f01..34ef756bb3b7 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -3482,6 +3482,7 @@ static int fd_locked_ioctl(struct block_device *bdev, blk_mode_t mode,
 		memcpy(&inparam.g, outparam,
 				offsetof(struct floppy_struct, name));
 		outparam = &inparam.g;
+		return fd_copyout((void __user *)param, outparam, size);
 		break;
 	case FDMSGON:
 		drive_params[drive].flags |= FTD_MSG;
@@ -3515,6 +3516,7 @@ static int fd_locked_ioctl(struct block_device *bdev, blk_mode_t mode,
 		return 0;
 	case FDGETMAXERRS:
 		outparam = &drive_params[drive].max_errors;
+		return fd_copyout((void __user *)param, outparam, size);
 		break;
 	case FDSETMAXERRS:
 		drive_params[drive].max_errors = inparam.max_errors;
@@ -3522,6 +3524,7 @@ static int fd_locked_ioctl(struct block_device *bdev, blk_mode_t mode,
 	case FDGETDRVTYP:
 		outparam = drive_name(type, drive);
 		SUPBOUND(size, strlen((const char *)outparam) + 1);
+		return fd_copyout((void __user *)param, outparam, size);
 		break;
 	case FDSETDRVPRM:
 		if (!valid_floppy_drive_params(inparam.dp.autodetect,
@@ -3531,6 +3534,7 @@ static int fd_locked_ioctl(struct block_device *bdev, blk_mode_t mode,
 		break;
 	case FDGETDRVPRM:
 		outparam = &drive_params[drive];
+		return fd_copyout((void __user *)param, outparam, size);
 		break;
 	case FDPOLLDRVSTAT:
 		if (lock_fdc(drive))
@@ -3541,17 +3545,20 @@ static int fd_locked_ioctl(struct block_device *bdev, blk_mode_t mode,
 		fallthrough;
 	case FDGETDRVSTAT:
 		outparam = &drive_state[drive];
+		return fd_copyout((void __user *)param, outparam, size);
 		break;
 	case FDRESET:
 		return user_reset_fdc(drive, (int)param, true);
 	case FDGETFDCSTAT:
 		outparam = &fdc_state[FDC(drive)];
+		return fd_copyout((void __user *)param, outparam, size);
 		break;
 	case FDWERRORCLR:
 		memset(&write_errors[drive], 0, sizeof(write_errors[drive]));
 		return 0;
 	case FDWERRORGET:
 		outparam = &write_errors[drive];
+		return fd_copyout((void __user *)param, outparam, size);
 		break;
 	case FDRAWCMD:
 		return floppy_raw_cmd_ioctl(type, drive, cmd, (void __user *)param);
@@ -3565,9 +3572,6 @@ static int fd_locked_ioctl(struct block_device *bdev, blk_mode_t mode,
 		return -EINVAL;
 	}
 
-	if (_IOC_DIR(cmd) & _IOC_READ)
-		return fd_copyout((void __user *)param, outparam, size);
-
 	return 0;
 }
 
-- 
2.34.1
Re: [PATCH] block: floppy: fix uninitialized use of outparam in fd_locked_ioctl
Posted by Denis Efremov 2 months, 3 weeks ago 
Hello,

Thank you for the report!

On 06/07/2025 11:22, Purva Yeshi wrote:
> Fix Smatch-detected error:
> drivers/block/floppy.c:3569 fd_locked_ioctl() error:
> uninitialized symbol 'outparam'.
> 

This a false-positive diagnostic. Smatch doesn't see the dependency
between FDGET... commands and _IOC_READ.

> Use the outparam pointer only after it is explicitly initialized.
> Previously, fd_copyout() was called unconditionally after the switch-case
> statement, assuming outparam would always be set when _IOC_READ was active.

        if (_IOC_DIR(cmd) & _IOC_READ)
                return fd_copyout((void __user *)param, outparam, size);

and all FDGET... macro are defined as _IOR(...).

> However, not all paths ensured this, which led to potential use of an
> uninitialized pointer.

Not all paths, but commands that fall under _IOC_READ condition. 

> 
> Move fd_copyout() calls directly into the relevant case blocks immediately
> after outparam is set. This ensures it is only called when safe and
> applicable.

If you want to suppress this "error" you can just initialize outparam
to NULL.

> 
> Signed-off-by: Purva Yeshi <purvayeshi550@gmail.com>
> ---
>  drivers/block/floppy.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
> index e97432032f01..34ef756bb3b7 100644
> --- a/drivers/block/floppy.c
> +++ b/drivers/block/floppy.c
> @@ -3482,6 +3482,7 @@ static int fd_locked_ioctl(struct block_device *bdev, blk_mode_t mode,
>  		memcpy(&inparam.g, outparam,
>  				offsetof(struct floppy_struct, name));
>  		outparam = &inparam.g;
> +		return fd_copyout((void __user *)param, outparam, size);
>  		break;
>  	case FDMSGON:
>  		drive_params[drive].flags |= FTD_MSG;
> @@ -3515,6 +3516,7 @@ static int fd_locked_ioctl(struct block_device *bdev, blk_mode_t mode,
>  		return 0;
>  	case FDGETMAXERRS:
>  		outparam = &drive_params[drive].max_errors;
> +		return fd_copyout((void __user *)param, outparam, size);
>  		break;
>  	case FDSETMAXERRS:
>  		drive_params[drive].max_errors = inparam.max_errors;
> @@ -3522,6 +3524,7 @@ static int fd_locked_ioctl(struct block_device *bdev, blk_mode_t mode,
>  	case FDGETDRVTYP:
>  		outparam = drive_name(type, drive);
>  		SUPBOUND(size, strlen((const char *)outparam) + 1);
> +		return fd_copyout((void __user *)param, outparam, size);
>  		break;
>  	case FDSETDRVPRM:
>  		if (!valid_floppy_drive_params(inparam.dp.autodetect,
> @@ -3531,6 +3534,7 @@ static int fd_locked_ioctl(struct block_device *bdev, blk_mode_t mode,
>  		break;
>  	case FDGETDRVPRM:
>  		outparam = &drive_params[drive];
> +		return fd_copyout((void __user *)param, outparam, size);
>  		break;
>  	case FDPOLLDRVSTAT:
>  		if (lock_fdc(drive))
> @@ -3541,17 +3545,20 @@ static int fd_locked_ioctl(struct block_device *bdev, blk_mode_t mode,
>  		fallthrough;
>  	case FDGETDRVSTAT:
>  		outparam = &drive_state[drive];
> +		return fd_copyout((void __user *)param, outparam, size);
>  		break;
>  	case FDRESET:
>  		return user_reset_fdc(drive, (int)param, true);
>  	case FDGETFDCSTAT:
>  		outparam = &fdc_state[FDC(drive)];
> +		return fd_copyout((void __user *)param, outparam, size);
>  		break;
>  	case FDWERRORCLR:
>  		memset(&write_errors[drive], 0, sizeof(write_errors[drive]));
>  		return 0;
>  	case FDWERRORGET:
>  		outparam = &write_errors[drive];
> +		return fd_copyout((void __user *)param, outparam, size);
>  		break;
>  	case FDRAWCMD:
>  		return floppy_raw_cmd_ioctl(type, drive, cmd, (void __user *)param);
> @@ -3565,9 +3572,6 @@ static int fd_locked_ioctl(struct block_device *bdev, blk_mode_t mode,
>  		return -EINVAL;
>  	}
>  
> -	if (_IOC_DIR(cmd) & _IOC_READ)
> -		return fd_copyout((void __user *)param, outparam, size);
> -
>  	return 0;
>  }
>  

Thanks,
Denis
Re: [PATCH] block: floppy: fix uninitialized use of outparam in fd_locked_ioctl
Posted by Purva Yeshi 2 months, 3 weeks ago 
On 13/07/25 00:46, Denis Efremov wrote:
> Hello,
> 
> Thank you for the report!
> 
> On 06/07/2025 11:22, Purva Yeshi wrote:
>> Fix Smatch-detected error:
>> drivers/block/floppy.c:3569 fd_locked_ioctl() error:
>> uninitialized symbol 'outparam'.
>>
> 
> This a false-positive diagnostic. Smatch doesn't see the dependency
> between FDGET... commands and _IOC_READ.

Hi Denis,

Thank you for the detailed explanation and for reviewing patch.

> 
>> Use the outparam pointer only after it is explicitly initialized.
>> Previously, fd_copyout() was called unconditionally after the switch-case
>> statement, assuming outparam would always be set when _IOC_READ was active.
> 
>          if (_IOC_DIR(cmd) & _IOC_READ)
>                  return fd_copyout((void __user *)param, outparam, size);
> 
> and all FDGET... macro are defined as _IOR(...).

Yes, I see it now.
All FDGET... commands that would enter the _IOC_READ block do initialize 
`outparam`, so it's guaranteed to be safe.

> 
>> However, not all paths ensured this, which led to potential use of an
>> uninitialized pointer.
> 
> Not all paths, but commands that fall under _IOC_READ condition.

Got it.

> 
>>
>> Move fd_copyout() calls directly into the relevant case blocks immediately
>> after outparam is set. This ensures it is only called when safe and
>> applicable.
> 
> If you want to suppress this "error" you can just initialize outparam
> to NULL.

I’ll update the patch to just initialize `outparam` to NULL to suppress 
the warning.

I’ll send a v2 patch soon.

> 
>>
>> Signed-off-by: Purva Yeshi <purvayeshi550@gmail.com>
>> ---
>>   drivers/block/floppy.c | 10 +++++++---
>>   1 file changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
>> index e97432032f01..34ef756bb3b7 100644
>> --- a/drivers/block/floppy.c
>> +++ b/drivers/block/floppy.c
>> @@ -3482,6 +3482,7 @@ static int fd_locked_ioctl(struct block_device *bdev, blk_mode_t mode,
>>   		memcpy(&inparam.g, outparam,
>>   				offsetof(struct floppy_struct, name));
>>   		outparam = &inparam.g;
>> +		return fd_copyout((void __user *)param, outparam, size);
>>   		break;
>>   	case FDMSGON:
>>   		drive_params[drive].flags |= FTD_MSG;
>> @@ -3515,6 +3516,7 @@ static int fd_locked_ioctl(struct block_device *bdev, blk_mode_t mode,
>>   		return 0;
>>   	case FDGETMAXERRS:
>>   		outparam = &drive_params[drive].max_errors;
>> +		return fd_copyout((void __user *)param, outparam, size);
>>   		break;
>>   	case FDSETMAXERRS:
>>   		drive_params[drive].max_errors = inparam.max_errors;
>> @@ -3522,6 +3524,7 @@ static int fd_locked_ioctl(struct block_device *bdev, blk_mode_t mode,
>>   	case FDGETDRVTYP:
>>   		outparam = drive_name(type, drive);
>>   		SUPBOUND(size, strlen((const char *)outparam) + 1);
>> +		return fd_copyout((void __user *)param, outparam, size);
>>   		break;
>>   	case FDSETDRVPRM:
>>   		if (!valid_floppy_drive_params(inparam.dp.autodetect,
>> @@ -3531,6 +3534,7 @@ static int fd_locked_ioctl(struct block_device *bdev, blk_mode_t mode,
>>   		break;
>>   	case FDGETDRVPRM:
>>   		outparam = &drive_params[drive];
>> +		return fd_copyout((void __user *)param, outparam, size);
>>   		break;
>>   	case FDPOLLDRVSTAT:
>>   		if (lock_fdc(drive))
>> @@ -3541,17 +3545,20 @@ static int fd_locked_ioctl(struct block_device *bdev, blk_mode_t mode,
>>   		fallthrough;
>>   	case FDGETDRVSTAT:
>>   		outparam = &drive_state[drive];
>> +		return fd_copyout((void __user *)param, outparam, size);
>>   		break;
>>   	case FDRESET:
>>   		return user_reset_fdc(drive, (int)param, true);
>>   	case FDGETFDCSTAT:
>>   		outparam = &fdc_state[FDC(drive)];
>> +		return fd_copyout((void __user *)param, outparam, size);
>>   		break;
>>   	case FDWERRORCLR:
>>   		memset(&write_errors[drive], 0, sizeof(write_errors[drive]));
>>   		return 0;
>>   	case FDWERRORGET:
>>   		outparam = &write_errors[drive];
>> +		return fd_copyout((void __user *)param, outparam, size);
>>   		break;
>>   	case FDRAWCMD:
>>   		return floppy_raw_cmd_ioctl(type, drive, cmd, (void __user *)param);
>> @@ -3565,9 +3572,6 @@ static int fd_locked_ioctl(struct block_device *bdev, blk_mode_t mode,
>>   		return -EINVAL;
>>   	}
>>   
>> -	if (_IOC_DIR(cmd) & _IOC_READ)
>> -		return fd_copyout((void __user *)param, outparam, size);
>> -
>>   	return 0;
>>   }
>>   
> 
> Thanks,
> Denis

Best regards,
Purva Yeshi

>

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