[PATCH v6 1/9] libata: fix ata_host_alloc_pinfo()

[Damien Le Moal <damien.lemoal@wdc.com>]

Avoid static checkers warnings about a potential NULL pointer
dereference for the port info variable pi. To do so, test that at least
one port info is available on entry to ata_host_alloc_pinfo() and start
the ata port initialization for() loop with pi initialized to the first
port info passed as argument (which is already checked to be non NULL).
Within the for() loop, get the next port info, if it is not NULL,
after initializing the ata port using the previous port info.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
 drivers/ata/libata-core.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 61c762961ca8..b237a718ea0f 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -5441,16 +5441,17 @@ struct ata_host *ata_host_alloc_pinfo(struct device *dev,
 	struct ata_host *host;
 	int i, j;
 
+	/* We must have at least one port info */
+	if (!ppi[0])
+		return NULL;
+
 	host = ata_host_alloc(dev, n_ports);
 	if (!host)
 		return NULL;
 
-	for (i = 0, j = 0, pi = NULL; i < host->n_ports; i++) {
+	for (i = 0, j = 0, pi = ppi[0]; i < host->n_ports; i++) {
 		struct ata_port *ap = host->ports[i];
 
-		if (ppi[j])
-			pi = ppi[j++];
-
 		ap->pio_mask = pi->pio_mask;
 		ap->mwdma_mask = pi->mwdma_mask;
 		ap->udma_mask = pi->udma_mask;
@@ -5460,6 +5461,15 @@ struct ata_host *ata_host_alloc_pinfo(struct device *dev,
 
 		if (!host->ops && (pi->port_ops != &ata_dummy_port_ops))
 			host->ops = pi->port_ops;
+
+		/*
+		 * Check that the next port info is not NULL.
+		 * If it is, keep using the current one.
+		 */
+		if (j < n_ports - 1 && ppi[j + 1]) {
+			j++;
+			pi = ppi[j];
+		}
 	}
 
 	return host;
-- 
2.31.1