linux-kernel - [PATCH] ata: libata-core: Fix possible null-pointer dereferences in ata_host_alloc

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Message-Id: <20190724030430.27788-1-baijiaju1990@gmail.com>
Date:   Wed, 24 Jul 2019 11:04:30 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     axboe@...nel.dk
Cc:     linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH] ata: libata-core: Fix possible null-pointer dereferences in ata_host_alloc_pinfo()

In ata_host_alloc_pinfo(), when ppi[j] is NULL (line 6184), pi is NULL.
In this case, pi is used on lines 6187-6195:
    ap->pio_mask = pi->pio_mask;
    ap->mwdma_mask = pi->mwdma_mask;
    ...
Thus, possible null-pointer dereferences may occur.

To fix these possible bugs, when ppi[j] is NULL, the loop continues, and
"j++" is moved to the loop's regulator.

These bugs are found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 drivers/ata/libata-core.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 28c492be0a57..dabfa50dfbbe 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -6178,11 +6178,13 @@ struct ata_host *ata_host_alloc_pinfo(struct device *dev,
 	if (!host)
 		return NULL;
 
-	for (i = 0, j = 0, pi = NULL; i < host->n_ports; i++) {
+	for (i = 0, j = 0, pi = NULL; i < host->n_ports; i++, j++) {
 		struct ata_port *ap = host->ports[i];
 
 		if (ppi[j])
-			pi = ppi[j++];
+			pi = ppi[j];
+		else
+			continue;
 
 		ap->pio_mask = pi->pio_mask;
 		ap->mwdma_mask = pi->mwdma_mask;
-- 
2.17.0