[PATCH 5.12 027/242] udf: Fix NULL pointer dereference in udf_symlink function

From: Greg Kroah-Hartman
Date: Thu Jul 15 2021 - 15:08:09 EST


From: Arturo Giusti <koredump@xxxxxxxxxxxxxx>

[ 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@xxxxxxxxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/udf/namei.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/fs/udf/namei.c b/fs/udf/namei.c
index f146b3089f3d..6c5692ad42b5 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);
--
2.30.2