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Subject[PATCH] storvsc: do not assume SG list is continuous when doing bounce buffers (for 4.1 stable only)
Date
From: Long Li <longli@microsoft.com>

This patch is for linux-stable 4.1 branch only.

storvsc checks the SG list for gaps before passing them to Hyper-v device.
If there are gaps, data is copied to a bounce buffer and a continuous data
buffer is passed to Hyper-V.

The check on gaps assumes SG list is continuous, and not chained. This is
not always true. Failing the check may result in incorrect I/O data
passed to the Hyper-v device.

This code path is not used post Linux 4.1.

Signed-off-by: Long Li <longli@microsoft.com>
---
drivers/scsi/storvsc_drv.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index 6c52d14..14dc5c6 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -584,17 +584,18 @@ static int do_bounce_buffer(struct scatterlist *sgl, unsigned int sg_count)
for (i = 0; i < sg_count; i++) {
if (i == 0) {
/* make sure 1st one does not have hole */
- if (sgl[i].offset + sgl[i].length != PAGE_SIZE)
+ if (sgl->offset + sgl->length != PAGE_SIZE)
return i;
} else if (i == sg_count - 1) {
/* make sure last one does not have hole */
- if (sgl[i].offset != 0)
+ if (sgl->offset != 0)
return i;
} else {
/* make sure no hole in the middle */
- if (sgl[i].length != PAGE_SIZE || sgl[i].offset != 0)
+ if (sgl->length != PAGE_SIZE || sgl->offset != 0)
return i;
}
+ sgl = sg_next(sgl);
}
return -1;
}
--
2.7.4
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