[PATCH 4.19 239/421] udf: Fix NULL pointer dereference in udf_symlink function

Greg Kroah-Hartman
2021-07-19T16:20:45Z

From: Arturo Giusti <koredump@protonmail.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@protonmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.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