[PATCH] IB/mthca: Fix possible uninitialized-variable access in mthca_SYS_EN()

[Tuo Li]

The variable out is declared without initialization, and its address is 
passed to mthca_cmd_imm():
  ret = mthca_cmd_imm(dev, 0, &out, 0, 0, CMD_SYS_EN, CMD_TIME_CLASS_D);

In this function, mthca_cmd_wait() or mthca_cmd_poll() will be called with 
the argument out_param, which is the address of the varialbe out. In these 
two called functions, mthca_cmd_post() will be called with *out_param, 
whose value comes from the uninitialized variable out.
  err = mthca_cmd_post(dev, in_param, out_param ? *out_param : 0, ...)

In mthca_cmd_post(), mthca_cmd_post_dbell() or mthca_cmd_post_hcr() will 
be called, in which the value from the uninitialized varialble out may be
used:
  __raw_writel((__force u32) cpu_to_be32(out_param >> 32), ptr + offs[3]);

To fix this possible uninitialized-variable access, initialized out to 0 
at the begining of mthca_SYS_EN().

Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx>
Signed-off-by: Tuo Li <islituo@xxxxxxxxx>
---
 drivers/infiniband/hw/mthca/mthca_cmd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/infiniband/hw/mthca/mthca_cmd.c b/drivers/infiniband/hw/mthca/mthca_cmd.c
index bdf5ed38de22..86584982e496 100644
--- a/drivers/infiniband/hw/mthca/mthca_cmd.c
+++ b/drivers/infiniband/hw/mthca/mthca_cmd.c
@@ -635,7 +635,7 @@ void mthca_free_mailbox(struct mthca_dev *dev, struct mthca_mailbox *mailbox)
 
 int mthca_SYS_EN(struct mthca_dev *dev)
 {
-	u64 out;
+	u64 out = 0;
 	int ret;
 
 	ret = mthca_cmd_imm(dev, 0, &out, 0, 0, CMD_SYS_EN, CMD_TIME_CLASS_D);
-- 
2.25.1