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