BUG: SCSI: usb storage SDHC card doesn't work in 2.6.27-rc1

[Matthew Frost <artusemrys@yahoo.com>]

James and co., 

Bug report: regression in 2.6.27-rc1 -- scsi WRT usb-storage
Origin: Commit de72aa4c2b82a6cffe15d86a8d391ded4fb57602, "[SCSI] erase
invalid data returned by device"
Location: drivers/scsi_lib.c
Device: Secure Digital HC 4GB card in USB 2.0 card reader

Summary:
Between 2.6.26-rc9-git10 and rc9-git11, the kernel stopped properly
recognizing my USB-card-reader-mounted SDHC 4GB card.  The problem seems to
come up between usb-storage recognizing the device, and the handoff to scsi
to read the disk properties.  The bug remains in 2.6.26 and 2.6.27-rc1;
kernels before 2.6.26-rc9-git10 are unaffected.  On the same EHCI controller,
an old-spec SD 1GB card and its reader are unaffected by this bug.

The normal recognition and initialization of the device (from rc9-git9 dmesg)
goes like this:

PCI: Setting latency timer of device 0000:00:1d.7 to 64
ehci_hcd 0000:00:1d.7: EHCI Host Controller
ehci_hcd 0000:00:1d.7: new USB bus registered, assigned bus number 1
PCI: cache line size of 128 is not supported by device 0000:00:1d.7
ehci_hcd 0000:00:1d.7: irq 23, io mem 0xe4000000
ehci_hcd 0000:00:1d.7: USB 2.0 started, EHCI 1.00, driver 10 Dec 2004
usb usb1: configuration #1 chosen from 1 choice
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 6 ports detected
usb usb1: New USB device found, idVendor=1d6b, idProduct=0002
usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
usb usb1: Product: EHCI Host Controller
usb usb1: Manufacturer: Linux 2.6.26-rc9-git9 ehci_hcd
usb usb1: SerialNumber: 0000:00:1d.7
--%<--
usb 1-1: new high speed USB device using ehci_hcd and address 2
usb 1-1: configuration #1 chosen from 1 choice
usb 1-1: New USB device found, idVendor=058f, idProduct=6331
usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 1-1: Product: Mass Storage Device
usb 1-1: Manufacturer: Generic
usb 1-1: SerialNumber: 058F091111B
--%<--
usb 1-2: new high speed USB device using ehci_hcd and address 3
usb 1-2: configuration #1 chosen from 1 choice
usb 1-2: New USB device found, idVendor=090c, idProduct=6000
usb 1-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 1-2: Product: USB2.0 Card Reader
usb 1-2: Manufacturer: Generic       ,   .
usb 1-2: SerialNumber: 12345678901234567890
--%<--
Initializing USB Mass Storage driver...
scsi4 : SCSI emulation for USB Mass Storage devices
usb-storage: device found at 2
usb-storage: waiting for device to settle before scanning
scsi5 : SCSI emulation for USB Mass Storage devices
usb-storage: device found at 3
usb-storage: waiting for device to settle before scanning
--%<--
usbcore: registered new interface driver usb-storage
USB Mass Storage support registered.
usbcore: registered new interface driver libusual
--%<--
usb-storage: device scan complete
scsi 4:0:0:0: Direct-Access     Multi    Flash Reader     1.00 PQ: 0 ANSI: 0
usb-storage: device scan complete
scsi 5:0:0:0: Direct-Access     Generic                   6000 PQ: 0 ANSI: 0
CCS
sd 4:0:0:0: [sde] 1953792 512-byte hardware sectors (1000 MB)
sd 4:0:0:0: [sde] Write Protect is off
sd 4:0:0:0: [sde] Mode Sense: 03 00 00 00
sd 4:0:0:0: [sde] Assuming drive cache: write through
sd 4:0:0:0: [sde] 1953792 512-byte hardware sectors (1000 MB)
sd 4:0:0:0: [sde] Write Protect is off
sd 4:0:0:0: [sde] Mode Sense: 03 00 00 00
sd 4:0:0:0: [sde] Assuming drive cache: write through
 sde: sde1
sd 4:0:0:0: [sde] Attached SCSI removable disk
sd 4:0:0:0: Attached scsi generic sg6 type 0
sd 5:0:0:0: [sdf] 7861248 512-byte hardware sectors (4025 MB)
sd 5:0:0:0: [sdf] Write Protect is off
sd 5:0:0:0: [sdf] Mode Sense: 4b 00 00 08
sd 5:0:0:0: [sdf] Assuming drive cache: write through
sd 5:0:0:0: [sdf] 7861248 512-byte hardware sectors (4025 MB)
sd 5:0:0:0: [sdf] Write Protect is off
sd 5:0:0:0: [sdf] Mode Sense: 4b 00 00 08
sd 5:0:0:0: [sdf] Assuming drive cache: write through
 sdf: sdf1
sd 5:0:0:0: [sdf] Attached SCSI removable disk
sd 5:0:0:0: Attached scsi generic sg7 type 0

(sde is the 1GB SD card/reader, sdf is the 4GB SDHC card/reader.)

After the bug, initialization looks the same until the device scan finishes. 
Handoff to scsi produces the following (taken from rc9-git12):

usb-storage: device scan complete
scsi 4:0:0:0: Direct-Access     Multi    Flash Reader     1.00 PQ: 0 ANSI: 0
usb-storage: device scan complete
scsi 5:0:0:0: Direct-Access     Generic                   6000 PQ: 0 ANSI: 0
CCS
sd 4:0:0:0: [sde] 1953792 512-byte hardware sectors (1000 MB)
sd 4:0:0:0: [sde] Write Protect is off
sd 4:0:0:0: [sde] Mode Sense: 03 00 00 00
sd 4:0:0:0: [sde] Assuming drive cache: write through
sd 4:0:0:0: [sde] 1953792 512-byte hardware sectors (1000 MB)
sd 4:0:0:0: [sde] Write Protect is off
sd 4:0:0:0: [sde] Mode Sense: 03 00 00 00
sd 4:0:0:0: [sde] Assuming drive cache: write through
 sde: sde1
sd 4:0:0:0: [sde] Attached SCSI removable disk
sd 4:0:0:0: Attached scsi generic sg6 type 0
sd 5:0:0:0: [sdf] Sector size 0 reported, assuming 512.
sd 5:0:0:0: [sdf] 1 512-byte hardware sectors (0 MB)
sd 5:0:0:0: [sdf] Write Protect is off
sd 5:0:0:0: [sdf] Mode Sense: 4b 00 00 08
sd 5:0:0:0: [sdf] Assuming drive cache: write through
sd 5:0:0:0: [sdf] Sector size 0 reported, assuming 512.
sd 5:0:0:0: [sdf] 1 512-byte hardware sectors (0 MB)
sd 5:0:0:0: [sdf] Write Protect is off
sd 5:0:0:0: [sdf] Mode Sense: 4b 00 00 08
sd 5:0:0:0: [sdf] Assuming drive cache: write through
 sdf: sdf1
 sdf: p1 exceeds device capacity
sd 5:0:0:0: [sdf] Attached SCSI removable disk
sd 5:0:0:0: Attached scsi generic sg7 type 0

And after boot, the following set of errors recurs until device removal.
Device removal, in this case, was necessary to get LILO to update (-git12
again):

attempt to access beyond end of device
sdf: rw=0, want=8200, limit=1
Buffer I/O error on device sdf1, logical block 0
attempt to access beyond end of device
sdf: rw=0, want=8208, limit=1
Buffer I/O error on device sdf1, logical block 1
attempt to access beyond end of device
sdf: rw=0, want=8216, limit=1
Buffer I/O error on device sdf1, logical block 2
attempt to access beyond end of device
sdf: rw=0, want=8224, limit=1
Buffer I/O error on device sdf1, logical block 3
attempt to access beyond end of device
sdf: rw=0, want=8200, limit=1
Buffer I/O error on device sdf1, logical block 0
attempt to access beyond end of device
sdf: rw=0, want=8200, limit=1
Buffer I/O error on device sdf1, logical block 0
attempt to access beyond end of device
sdf: rw=0, want=8208, limit=1
Buffer I/O error on device sdf1, logical block 1
attempt to access beyond end of device
sdf: rw=0, want=8216, limit=1
Buffer I/O error on device sdf1, logical block 2
attempt to access beyond end of device
sdf: rw=0, want=8224, limit=1
Buffer I/O error on device sdf1, logical block 3
attempt to access beyond end of device
sdf: rw=0, want=8200, limit=1
Buffer I/O error on device sdf1, logical block 0
attempt to access beyond end of device
sdf: rw=0, want=8200, limit=1
Buffer I/O error on device sdf1, logical block 0
attempt to access beyond end of device
sdf: rw=0, want=8208, limit=1
Buffer I/O error on device sdf1, logical block 1
attempt to access beyond end of device
sdf: rw=0, want=8216, limit=1
Buffer I/O error on device sdf1, logical block 2
attempt to access beyond end of device
sdf: rw=0, want=8224, limit=1
Buffer I/O error on device sdf1, logical block 3
attempt to access beyond end of device
sdf: rw=0, want=8200, limit=1
Buffer I/O error on device sdf1, logical block 0
usb 1-2: USB disconnect, address 3

I'm not well-versed in git, so I looked through the diff between rc9-git10
and rc9-git11.  This is what looks like the offending addition:

> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index a82d2fe..cbf55d5 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -207,6 +207,15 @@ int scsi_execute(struct scsi_device *sdev, const
unsigned char *cmd,
>  	 */
>  	blk_execute_rq(req->q, NULL, req, 1);
>  
> +	/*
> +	 * Some devices (USB mass-storage in particular) may transfer
> +	 * garbage data together with a residue indicating that the data
> +	 * is invalid.  Prevent the garbage from being misinterpreted
> +	 * and prevent security leaks by zeroing out the excess data.
> +	 */
> +	if (unlikely(req->data_len > 0 && req->data_len <= bufflen))
> +		memset(buffer + (bufflen - req->data_len), 0, req->data_len);
> +
>  	ret = req->errors;
>   out:
>  	blk_put_request(req);

I looked through the online git log, and it's part of commit
de72aa4c2b82a6cffe15d86a8d391ded4fb57602, under "[SCSI] erase invalid data
returned by device".  Reverting this part by itself restores the correct
handling of the device in 2.6.27-rc1.

Perhaps there's a better way to do what this patch is trying to do, because
it seems to be erasing the valid data returned by my device.  If you want me
to test out options, I'd be glad to, since I have the "offending" hardware. 
Specifics: A-Data 4GB TurboSD Class 6 SDHC card, 4GB, in a Rosewill RSD-CR102
card reader.

(Please include me on replies, I've stopped being a subscriber.)

Thanks!

Matthew Frost
artusemrys sbcglobal net