2018-03-01 14:10:21

by Jeremy Cline

Subject: [PATCH] scsi: sd: Keep disk read-only when re-reading partition

If the read-only flag is true on a SCSI disk, re-reading the partition
table sets the flag back to false.

To observe this bug, you can run:

1. blockdev --setro /dev/sda
2. blockdev --rereadpt /dev/sda
3. blockdev --getro /dev/sda

This commit reads the disk's old state and combines it with the device
disk-reported state rather than unconditionally marking it as RW.

Reported-by: Li Ning <[email protected]>
Signed-off-by: Jeremy Cline <[email protected]>
---
drivers/scsi/sd.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index bff21e636ddd..7a3a66a7890f 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2595,6 +2595,7 @@ sd_read_write_protect_flag(struct scsi_disk *sdkp, unsigned char *buffer)
int res;
struct scsi_device *sdp = sdkp->device;
struct scsi_mode_data data;
+ int disk_ro = get_disk_ro(sdkp->disk);
int old_wp = sdkp->write_prot;

set_disk_ro(sdkp->disk, 0);
@@ -2634,7 +2635,8 @@ sd_read_write_protect_flag(struct scsi_disk *sdkp, unsigned char *buffer)
sd_first_printk(KERN_WARNING, sdkp,
"Test WP failed, assume Write Enabled\n");
} else {
- sdkp->write_prot = ((data.device_specific & 0x80) != 0);
+ sdkp->write_prot = ((data.device_specific & 0x80) != 0) ||
+ disk_ro;
set_disk_ro(sdkp->disk, sdkp->write_prot);
if (sdkp->first_scan || old_wp != sdkp->write_prot) {
sd_printk(KERN_NOTICE, sdkp, "Write Protect is %s\n",
--
2.16.2

2018-03-01 14:16:11

by Andy Shevchenko

Subject: Re: [PATCH] scsi: sd: Keep disk read-only when re-reading partition

On Thu, Mar 1, 2018 at 4:08 PM, Jeremy Cline <[email protected]> wrote:
> If the read-only flag is true on a SCSI disk, re-reading the partition
> table sets the flag back to false.
>
> To observe this bug, you can run:
>
> 1. blockdev --setro /dev/sda
> 2. blockdev --rereadpt /dev/sda
> 3. blockdev --getro /dev/sda
>
> This commit reads the disk's old state and combines it with the device
> disk-reported state rather than unconditionally marking it as RW.

> - sdkp->write_prot = ((data.device_specific & 0x80) != 0);
> + sdkp->write_prot = ((data.device_specific & 0x80) != 0) ||
> + disk_ro;

Perhaps
sdkp->write_prot = (data.device_specific & 0x80) || disk_ro;

will save a line.

--
With Best Regards,
Andy Shevchenko

2018-03-02 02:04:12

by Martin K. Petersen

Subject: Re: [PATCH] scsi: sd: Keep disk read-only when re-reading partition

Jeremy,

Thanks for looking into this!

> This commit reads the disk's old state and combines it with the device
> disk-reported state rather than unconditionally marking it as RW.

Applied to 4.16/scsi-fixes with a few minor tweaks. Thank you!

--
Martin K. Petersen Oracle Linux Engineering

2018-03-02 15:13:52

by Johannes Thumshirn

Subject: Re: [PATCH] scsi: sd: Keep disk read-only when re-reading partition

On Thu, Mar 01, 2018 at 02:08:10PM +0000, Jeremy Cline wrote:
> If the read-only flag is true on a SCSI disk, re-reading the partition
> table sets the flag back to false.
>
> To observe this bug, you can run:
>
> 1. blockdev --setro /dev/sda
> 2. blockdev --rereadpt /dev/sda
> 3. blockdev --getro /dev/sda

hi Jeremy,

Do you mind wiring up a testcase in blktest [1] for this? Given that
you already have a rather trivial reproducer.

[1] https://github.com/osandov/

Thanks,
Johannes

--
Johannes Thumshirn Storage
[email protected] +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N?rnberg
GF: Felix Imend?rffer, Jane Smithard, Graham Norton
HRB 21284 (AG N?rnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850

2018-03-02 19:06:58

by Jeremy Cline

Subject: Re: [PATCH] scsi: sd: Keep disk read-only when re-reading partition

On 03/02/2018 07:00 AM, Johannes Thumshirn wrote:
> On Thu, Mar 01, 2018 at 02:08:10PM +0000, Jeremy Cline wrote:
>> If the read-only flag is true on a SCSI disk, re-reading the partition
>> table sets the flag back to false.
>>
>> To observe this bug, you can run:
>>
>> 1. blockdev --setro /dev/sda
>> 2. blockdev --rereadpt /dev/sda
>> 3. blockdev --getro /dev/sda
>
> hi Jeremy,
>
> Do you mind wiring up a testcase in blktest [1] for this? Given that
> you already have a rather trivial reproducer.
>
> [1] https://github.com/osandov/

Hi Johannes,

Sure, I'll take care of it.

Regards,
Jeremy

2018-03-02 19:07:43

by Johannes Thumshirn

Subject: Re: [PATCH] scsi: sd: Keep disk read-only when re-reading partition

On Fri, Mar 02, 2018 at 02:11:02PM +0000, Jeremy Cline wrote:
> Sure, I'll take care of it.

Thanks a lot.
Johannes
--
Johannes Thumshirn Storage
[email protected] +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N?rnberg
GF: Felix Imend?rffer, Jane Smithard, Graham Norton
HRB 21284 (AG N?rnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850