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libata: reject passthrough WRITE SAME requests

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commit c6ade20f5e 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>
[bwh: Backported to 3.2:
 - Open-code blk_rq_is_passthrough()
 - We don't distinguish which field is invaid so goto invalid_fld
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
This commit is contained in:
Christoph Hellwig
2017-04-25 13:39:54 +02:00
committed by Ben Hutchings
parent 258132a3ab
commit 4d34a500e7
1 changed files with 8 additions and 0 deletions
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8
drivers/ata/libata-scsi.c
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@ -3056,6 +3056,14 @@ static unsigned int ata_scsi_write_same_xlat(struct ata_queued_cmd *qc)
if (unlikely(!dev->dma_mode))
goto invalid_fld;
/*
* 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(scmd->request->cmd_type != REQ_TYPE_FS))
goto invalid_fld;
if (unlikely(scmd->cmd_len < 16))
goto invalid_fld;
scsi_16_lba_len(cdb, &block, &n_block);