From: Arturo Giusti <koredump@protonmail.com>
Date: Tue, 18 May 2021 10:34:57 +0000 (+0200)
Subject: udf: Fix NULL pointer dereference in udf_symlink function
X-Git-Tag: v5.12.18~209
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=aebed6b19e51a34003d998da5ebb1dfdd2cb1d02;p=thirdparty%2Fkernel%2Fstable.git

udf: Fix NULL pointer dereference in udf_symlink function

[ 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@protonmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/fs/udf/namei.c b/fs/udf/namei.c
index f146b3089f3da..6c5692ad42b55 100644
--- a/fs/udf/namei.c
+++ b/fs/udf/namei.c
@@ -934,6 +934,10 @@ static int udf_symlink(struct user_namespace *mnt_userns, struct inode *dir,
 				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);