[PATCH] scsi: dpt_i2o: fix a potential use-after-free in __adpt_reset()

[Hang Zhang <zh.nvgt@gmail.com>]

__adpt_reset() invokes adpt_hba_reset(), which can free "pHba"
on error paths and return an negative error code in those
situations. The problem is that "pHba" is from the global pointer
"cmd->device->host->hostdata[0]", regardless of the possible free
of "pHba", that original global pointer is never nullified and
thus may become a dangling pointer and be dereferenced later,
potentially causing a use-after-free.

Fix the issue by nullifying "cmd->device->host->hostdata[0]" if
adpt_hba_reset() returns a negative error code to __adpt_reset(),
which indicates the free of "pHba". Also add a NULL check before
any dereference of "pHba", or the aliased global pointer. Note
that the similar NULL check already exists at other places, like
in adpt_queue_lck().

Signed-off-by: Hang Zhang <zh.nvgt@gmail.com>
---
 drivers/scsi/dpt_i2o.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/scsi/dpt_i2o.c b/drivers/scsi/dpt_i2o.c
index 2e9155ba7408..9827517a1898 100644
--- a/drivers/scsi/dpt_i2o.c
+++ b/drivers/scsi/dpt_i2o.c
@@ -753,6 +753,9 @@ static int __adpt_reset(struct scsi_cmnd* cmd)
 	char name[32];
 
 	pHba = (adpt_hba*)cmd->device->host->hostdata[0];
+	if (!pHba) {
+		return FAILED;
+	}
 	strncpy(name, pHba->name, sizeof(name));
 	printk(KERN_WARNING"%s: Hba Reset: scsi id %d: tid: %d\n", name, cmd->device->channel, pHba->channel[cmd->device->channel].tid);
 	rcode =  adpt_hba_reset(pHba);
@@ -760,6 +763,7 @@ static int __adpt_reset(struct scsi_cmnd* cmd)
 		printk(KERN_WARNING"%s: HBA reset complete\n", name);
 		return SUCCESS;
 	} else {
+		cmd->device->host->hostdata[0] = NULL;
 		printk(KERN_WARNING"%s: HBA reset failed (%x)\n", name, rcode);
 		return FAILED;
 	}
-- 
2.39.0