From bc977749e967daa56de1922cf4cb38525631c51c Mon Sep 17 00:00:00 2001 From: Lukas Czerner Date: Thu, 16 Aug 2012 16:38:45 +0200 Subject: [PATCH] [SCSI] scsi_debug: Fix off-by-one bug when unmapping region Currently it is possible to unmap one more block than user requested to due to the off-by-one error in unmap_region(). This is probably due to the fact that the end variable despite its name actually points to the last block to unmap + 1. However in the condition it is handled as the last block of the region to unmap. The bug was not previously spotted probably due to the fact that the region was not zeroed, which has changed with commit be1dd78de5686c062bb3103f9e86d444a10ed783. With that commit we were able to corrupt the ext4 file system on 256M scsi_debug device with LBPRZ enabled using fstrim. Since the 'end' semantic is the same in several functions there this commit just fixes the condition to use the 'end' variable correctly in that context. Reported-by: Paolo Bonzini Signed-off-by: Lukas Czerner Reviewed-by: Martin K. Petersen Acked-by: Douglas Gilbert Cc: Signed-off-by: James Bottomley --- drivers/scsi/scsi_debug.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c index 57fbd5a3d4e2..5cda11c07c68 100644 --- a/drivers/scsi/scsi_debug.c +++ b/drivers/scsi/scsi_debug.c @@ -2055,7 +2055,7 @@ static void unmap_region(sector_t lba, unsigned int len) block = lba + alignment; rem = do_div(block, granularity); - if (rem == 0 && lba + granularity <= end && block < map_size) { + if (rem == 0 && lba + granularity < end && block < map_size) { clear_bit(block, map_storep); if (scsi_debug_lbprz) memset(fake_storep +