linux-kernel - [PATCH] media: davinci_vpfe: fix a NULL pointer dereference bug

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Message-Id: <1538668833-18372-1-git-send-email-wang6495@umn.edu>
Date:   Thu,  4 Oct 2018 11:00:31 -0500
From:   Wenwen Wang <wang6495@....edu>
To:     Wenwen Wang <wang6495@....edu>
Cc:     Kangjie Lu <kjlu@....edu>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-media@...r.kernel.org (open list:MEDIA INPUT INFRASTRUCTURE
        (V4L/DVB)),
        devel@...verdev.osuosl.org (open list:STAGING SUBSYSTEM),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] media: davinci_vpfe: fix a NULL pointer dereference bug

In vpfe_isif_init(), there is a while loop to get the ISIF base address and
linearization table0 and table1 address. In the loop body, the function
platform_get_resource() is called to get the resource. If
platform_get_resource() returns NULL, the loop is terminated and the
execution goes to 'fail_nobase_res'. Suppose the loop is terminated at the
first iteration because platform_get_resource() returns NULL and the
execution goes to 'fail_nobase_res'. Given that there is another while loop
at 'fail_nobase_res' and i equals to 0, one iteration of the second while
loop will be executed. However, the second while loop does not check the
return value of platform_get_resource(). This can cause a NULL pointer
dereference bug if the return value is a NULL pointer.

This patch avoids the above issue by adding a check in the second while
loop after the call to platform_get_resource().

Signed-off-by: Wenwen Wang <wang6495@....edu>
---
 drivers/staging/media/davinci_vpfe/dm365_isif.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/media/davinci_vpfe/dm365_isif.c b/drivers/staging/media/davinci_vpfe/dm365_isif.c
index 745e33f..b0425a6 100644
--- a/drivers/staging/media/davinci_vpfe/dm365_isif.c
+++ b/drivers/staging/media/davinci_vpfe/dm365_isif.c
@@ -2080,7 +2080,8 @@ int vpfe_isif_init(struct vpfe_isif_device *isif, struct platform_device *pdev)

 	while (i >= 0) {
 		res = platform_get_resource(pdev, IORESOURCE_MEM, i);
-		release_mem_region(res->start, res_len);
+		if (res)
+			release_mem_region(res->start, res_len);
 		i--;
 	}
 	return status;
-- 
2.7.4