scsi: fix memory leak with scsi-mq

Fix a memory leak with scsi-mq triggered by commands with large data
transfer length.

__sg_alloc_table() sets both table->nents and table->orig_nents to the
same value.  When the scatterlist is DMA-mapped, table->nents is
overwritten with the (possibly smaller) size of the DMA-mapped
scatterlist, while table->orig_nents retains the original size of the
allocated scatterlist.  scsi_free_sgtable() should therefore check
orig_nents instead of nents, and all code that initializes sdb->table
without calling __sg_alloc_table() should set both nents and orig_nents.

Fixes: d285203cf647 ("scsi: add support for a blk-mq based I/O path.")
Cc: <stable@vger.kernel.org> # 3.17+
Signed-off-by: Tony Battersby <tonyb@cybernetics.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Odin.com>

2 files changed, 4 insertions, 4 deletions

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 106884a5444e..cfadccef045c 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -944,7 +944,7 @@ void scsi_eh_prep_cmnd(struct scsi_cmnd *scmd, struct scsi_eh_save *ses,
                             scmd->sdb.length);
                 scmd->sdb.table.sgl = &ses->sense_sgl;
                 scmd->sc_data_direction = DMA_FROM_DEVICE;
-                scmd->sdb.table.nents = 1;
+                scmd->sdb.table.nents = scmd->sdb.table.orig_nents = 1;
                 scmd->cmnd[0] = REQUEST_SENSE;
                 scmd->cmnd[4] = scmd->sdb.length;
                 scmd->cmd_len = COMMAND_SIZE(scmd->cmnd[0]);
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index b1a263137a23..448ebdaa3d69 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -583,7 +583,7 @@ static struct scatterlist *scsi_sg_alloc(unsigned int nents, gfp_t gfp_mask)
 
 static void scsi_free_sgtable(struct scsi_data_buffer *sdb, bool mq)
 {
-        if (mq && sdb->table.nents <= SCSI_MAX_SG_SEGMENTS)
+        if (mq && sdb->table.orig_nents <= SCSI_MAX_SG_SEGMENTS)
                 return;
         __sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS, mq, scsi_sg_free);
 }
@@ -597,8 +597,8 @@ static int scsi_alloc_sgtable(struct scsi_data_buffer *sdb, int nents, bool mq)
 
         if (mq) {
                 if (nents <= SCSI_MAX_SG_SEGMENTS) {
-                        sdb->table.nents = nents;
-                        sg_init_table(sdb->table.sgl, sdb->table.nents);
+                        sdb->table.nents = sdb->table.orig_nents = nents;
+                        sg_init_table(sdb->table.sgl, nents);
                         return 0;
                 }
                 first_chunk = sdb->table.sgl;