scsi: target/iblock: Fix overrun in WRITE SAME emulation

commit 5676234f20fef02f6ca9bd66c63a8860fce62645 upstream.

WRITE SAME corrupts data on the block device behind iblock if the command
is emulated. The emulation code issues (M - 1) * N times more bios than
requested, where M is the number of 512 blocks per real block size and N is
the NUMBER OF LOGICAL BLOCKS specified in WRITE SAME command. So, for a
device with 4k blocks, 7 * N more LBAs gets written after the requested
range.

The issue happens because the number of 512 byte sectors to be written is
decreased one by one while the real bios are typically from 1 to 8 512 byte
sectors per bio.

Fixes: c66ac9db8d4a ("[SCSI] target: Add LIO target core v4.0.0-rc6")
Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
[bwh: Backported to 3.16: use IBLOCK_LBA_SHIFT instead of SECTOR_SHIFT]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/target/target_core_iblock.c b/drivers/target/target_core_iblock.c
index 7ee927d9c3ac070248f50690f45d51ea59ecbe0c..f9d811a9146cdb11a5551f5434913a535592fae2 100644 (file)
--- a/drivers/target/target_core_iblock.c
+++ b/drivers/target/target_core_iblock.c
@@ -490,7 +490,7 @@ iblock_execute_write_same(struct se_cmd *cmd)
 
                /* Always in 512 byte units for Linux/Block */
                block_lba += sg->length >> IBLOCK_LBA_SHIFT;
-               sectors -= 1;
+               sectors -= sg->length >> IBLOCK_LBA_SHIFT;
        }
 
        iblock_submit_bios(&list, WRITE);