[PATCH AUTOSEL 4.14 14/45] udf: Fix NULL pointer dereference in udf_symlink function

From: Sasha Levin
Date: Tue Jul 06 2021 - 08:03:04 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 041bf34f781f..d5516f025bad 100644
--- a/fs/udf/namei.c
+++ b/fs/udf/namei.c
@@ -956,6 +956,10 @@ static int udf_symlink(struct inode *dir, struct dentry *dentry,
epos.bh = udf_tgetblk(sb, block);
+ if (unlikely(!epos.bh)) {
+ err = -ENOMEM;
+ goto out_no_entry;
+ }
memset(epos.bh->b_data, 0x00, bsize);