[PATCH 4.11 106/114] libata: reject passthrough WRITE SAME requests

[Greg Kroah-Hartman]

4.11-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Christoph Hellwig <hch@xxxxxx>

commit c6ade20f5e50e188d20b711a618b20dd1d50457e upstream.

The WRITE SAME to TRIM translation rewrites the DATA OUT buffer.  While
the SCSI code accomodates for this by passing a read-writable buffer
userspace applications don't cater for this behavior.  In fact it can
be used to rewrite e.g. a readonly file through mmap and should be
considered as a security fix.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/ata/libata-scsi.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -3462,6 +3462,14 @@ static unsigned int ata_scsi_write_same_
 	if (unlikely(!dev->dma_mode))
 		goto invalid_opcode;
 
+	/*
+	 * We only allow sending this command through the block layer,
+	 * as it modifies the DATA OUT buffer, which would corrupt user
+	 * memory for SG_IO commands.
+	 */
+	if (unlikely(blk_rq_is_passthrough(scmd->request)))
+		goto invalid_opcode;
+
 	if (unlikely(scmd->cmd_len < 16)) {
 		fp = 15;
 		goto invalid_fld;