diff mbox series

[1/1] udf: Fix null-ptr-deref in udf_write_fi()

Message ID 20230107195016.290627-2-pchelkin@ispras.ru
State New
Headers
Series udf: Fix null-ptr-deref in udf_write_fi() |

Commit Message

Fedor Pchelkin Jan. 7, 2023, 7:50 p.m. UTC 
  udf_find_entry() can return NULL or an error pointer if it fails. So we
should check its return value to avoid NULL pointer dereferencing in
udf_write_fi() (which is called from udf_delete_entry()). Also, if
udf_find_entry() returns an error pointer, it is possible that ofibh and
ocfi structs hold invalid values which can cause additional problems in
udf_write_fi().

If udf_find_entry() returns an error pointer, udf_rename() should return
with an error code. If udf_find_entry() returns NULL, ofi has probably
already been deleted.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Fixes: 231473f6ddce ("udf: Return error from udf_find_entry()")
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: syzbot+8a5a459f324d510ea15a@syzkaller.appspotmail.com
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
---
 fs/udf/namei.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Comments

Jan Kara Jan. 9, 2023, 9:44 a.m. UTC | #1 
On Sat 07-01-23 22:50:16, Fedor Pchelkin wrote:
> udf_find_entry() can return NULL or an error pointer if it fails. So we
> should check its return value to avoid NULL pointer dereferencing in
> udf_write_fi() (which is called from udf_delete_entry()). Also, if
> udf_find_entry() returns an error pointer, it is possible that ofibh and
> ocfi structs hold invalid values which can cause additional problems in
> udf_write_fi().
> 
> If udf_find_entry() returns an error pointer, udf_rename() should return
> with an error code. If udf_find_entry() returns NULL, ofi has probably
> already been deleted.
> 
> Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
> 
> Fixes: 231473f6ddce ("udf: Return error from udf_find_entry()")
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Reported-by: syzbot+8a5a459f324d510ea15a@syzkaller.appspotmail.com
> Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
> Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>

Thanks for the patch but I have already queued in my tree [1] rewrite of
UDF directory handling code that addresses multiple issues syzbot found in
directory handling and as far as I'm looking into the new code, this one
should be fixed as well.

[1] git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs.git for_next

								Honza
diff mbox series

Patch

diff --git a/fs/udf/namei.c b/fs/udf/namei.c
index 7c95c549dd64..6b058c6ebf93 100644
--- a/fs/udf/namei.c
+++ b/fs/udf/namei.c
@@ -1170,7 +1170,12 @@  static int udf_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
 
 	/* The old fid may have moved - find it again */
 	ofi = udf_find_entry(old_dir, &old_dentry->d_name, &ofibh, &ocfi);
-	udf_delete_entry(old_dir, ofi, &ofibh, &ocfi);
+	if (ofi && IS_ERR(ofi)) {
+		retval = PTR_ERR(ofi);
+		goto end_rename;
+	} else if (ofi) {
+		udf_delete_entry(old_dir, ofi, &ofibh, &ocfi);
+	}
 
 	if (new_inode) {
 		new_inode->i_ctime = current_time(new_inode);