linux-kernel - [PATCH AUTOSEL 5.4 09/23] ata: libata-core: fix NULL pointer deref in ata_host_alloc

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Date:   Mon, 13 Jun 2022 22:08:45 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Sergey Shtylyov <s.shtylyov@....ru>,
        Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        Sasha Levin <sashal@...nel.org>, tj@...nel.org,
        linux-ide@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 09/23] ata: libata-core: fix NULL pointer deref in ata_host_alloc_pinfo()

From: Sergey Shtylyov <s.shtylyov@....ru>

[ Upstream commit bf476fe22aa1851bab4728e0c49025a6a0bea307 ]

In an unlikely (and probably wrong?) case that the 'ppi' parameter of
ata_host_alloc_pinfo() points to an array starting with a NULL pointer,
there's going to be a kernel oops as the 'pi' local variable won't get
reassigned from the initial value of NULL. Initialize 'pi' instead to
'&ata_dummy_port_info' to fix the possible kernel oops for good...

Found by Linux Verification Center (linuxtesting.org) with the SVACE static
analysis tool.

Signed-off-by: Sergey Shtylyov <s.shtylyov@....ru>
Signed-off-by: Damien Le Moal <damien.lemoal@...nsource.wdc.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/ata/libata-core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index af8a1bac9345..fc37e075f3e1 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -6235,7 +6235,7 @@ struct ata_host *ata_host_alloc_pinfo(struct device *dev,
 				      const struct ata_port_info * const * ppi,
 				      int n_ports)
 {
-	const struct ata_port_info *pi;
+	const struct ata_port_info *pi = &ata_dummy_port_info;
 	struct ata_host *host;
 	int i, j;
 
@@ -6243,7 +6243,7 @@ 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; i < host->n_ports; i++) {
 		struct ata_port *ap = host->ports[i];
 
 		if (ppi[j])
-- 
2.35.1