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[SCSI] erase invalid data returned by device

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This patch (as1108) fixes a problem that can occur with certain USB
mass-storage devices: They return invalid data together with a residue
indicating that the data should be ignored.  Rather than leave the
invalid data in a transfer buffer, where it can get misinterpreted,
the patch clears the invalid portion of the buffer.

This solves a problem (wrong write-protect setting detected) reported
by Maciej Rutecki and Peter Teoh.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Peter Teoh <htmldeveloper@gmail.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
This commit is contained in:
Alan Stern 2008-06-24 14:03:14 -04:00 committed by James Bottomley
parent b7279469d6
commit bdb2b8cab4
1 changed files with 9 additions and 0 deletions
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9
drivers/scsi/scsi_lib.c
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@ -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);