libata: reject passthrough WRITE SAME requests

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@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 1ac70744ae7b4b2dc6c4ce4f339b87740921e15f..50f56d0669364f8db4cb6e206ee6ac879b8f25cf 100644 (file)
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -3462,6 +3462,14 @@ static unsigned int ata_scsi_write_same_xlat(struct ata_queued_cmd *qc)
        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;