[PATCH] ixgbe: fix incomplete ACI command buffer backup on retry

[Linkui Xiao <xiaolinkui@126.com>]

From: Linkui Xiao <xiaolinkui@kylinos.cn>

ixgbe_aci_send_cmd() backs up the indirect command buffer so that it can
be restored before an EBUSY retry, but the backup only copies the very
first byte of it:

    buf_cpy = kmalloc(buf_size, GFP_KERNEL);
    ...
    *buf_cpy = *(u8 *)buf;

while the restore path copies the full buffer back out of it:

    if (buf)
        memcpy(buf, buf_cpy, buf_size);

So every retry hands the firmware a buffer whose content, apart from the
first byte, is uninitialized slab memory, and on a read command the
caller's buffer is overwritten with that garbage when the retry finally
gives up. The buffer of a read command is an output buffer, so the caller
does not initialize it either.

Use kmemdup() to copy the whole buffer, exactly like the equivalent
ice_sq_send_cmd() already does.

Also skip the backup when buf_size is 0. kmalloc(0) returns
ZERO_SIZE_PTR and the single byte store above would write to it, and
restore based on buf_cpy instead of buf so that this case never passes
ZERO_SIZE_PTR to memcpy().

Fixes: 46761fd52a88 ("ixgbe: Add support for E610 FW Admin Command Interface")
Signed-off-by: Linkui Xiao <xiaolinkui@kylinos.cn>
---
 drivers/net/ethernet/intel/ixgbe/ixgbe_e610.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_e610.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_e610.c
index 4d8ae5b56145..5dd88ee7ea58 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_e610.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_e610.c
@@ -214,11 +214,10 @@ int ixgbe_aci_send_cmd(struct ixgbe_hw *hw, struct libie_aq_desc *desc,
 
 	is_cmd_for_retry = ixgbe_should_retry_aci_send_cmd_execute(opcode);
 	if (is_cmd_for_retry) {
-		if (buf) {
-			buf_cpy = kmalloc(buf_size, GFP_KERNEL);
+		if (buf && buf_size) {
+			buf_cpy = kmemdup(buf, buf_size, GFP_KERNEL);
 			if (!buf_cpy)
 				return -ENOMEM;
-			*buf_cpy = *(u8 *)buf;
 		}
 		desc_cpy = *desc;
 	}
@@ -234,7 +233,7 @@ int ixgbe_aci_send_cmd(struct ixgbe_hw *hw, struct libie_aq_desc *desc,
 		    last_status != LIBIE_AQ_RC_EBUSY)
 			break;
 
-		if (buf)
+		if (buf_cpy)
 			memcpy(buf, buf_cpy, buf_size);
 		*desc = desc_cpy;
 
-- 
2.25.1