linux-kernel - [PATCH 4.19 239/421] udf: Fix NULL pointer dereference in udf

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Date:   Mon, 19 Jul 2021 16:50:50 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Arturo Giusti <koredump@...tonmail.com>,
        Jan Kara <jack@...e.cz>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 239/421] udf: Fix NULL pointer dereference in udf_symlink function

From: Arturo Giusti <koredump@...tonmail.com>

[ Upstream commit fa236c2b2d4436d9f19ee4e5d5924e90ffd7bb43 ]

In function udf_symlink, epos.bh is assigned with the value returned
by udf_tgetblk. The function udf_tgetblk is defined in udf/misc.c
and returns the value of sb_getblk function that could be NULL.
Then, epos.bh is used without any check, causing a possible
NULL pointer dereference when sb_getblk fails.

This fix adds a check to validate the value of epos.bh.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=213083
Signed-off-by: Arturo Giusti <koredump@...tonmail.com>
Signed-off-by: Jan Kara <jack@...e.cz>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/udf/namei.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/udf/namei.c b/fs/udf/namei.c
index 58cc2414992b..9cfb555db1ad 100644
--- a/fs/udf/namei.c
+++ b/fs/udf/namei.c
@@ -948,6 +948,10 @@ static int udf_symlink(struct inode *dir, struct dentry *dentry,
 				iinfo->i_location.partitionReferenceNum,
 				0);
 		epos.bh = udf_tgetblk(sb, block);
+		if (unlikely(!epos.bh)) {
+			err = -ENOMEM;
+			goto out_no_entry;
+		}
 		lock_buffer(epos.bh);
 		memset(epos.bh->b_data, 0x00, bsize);
 		set_buffer_uptodate(epos.bh);
-- 
2.30.2