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authorPavel Shilovsky <pshilov@microsoft.com>2019-11-27 16:18:39 -0800
committerSteve French <stfrench@microsoft.com>2019-12-02 15:15:00 -0600
commit6f582b273ec23332074d970a7fb25bef835df71f (patch)
treedde3c85d4586e46485cb03fdf5730afbbf82529c /fs
parent21b26d2679584c6a60e861aa3e5ca09a6bab0633 (diff)
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CIFS: Fix NULL-pointer dereference in smb2_push_mandatory_locks
Currently when the client creates a cifsFileInfo structure for a newly opened file, it allocates a list of byte-range locks with a pointer to the new cfile and attaches this list to the inode's lock list. The latter happens before initializing all other fields, e.g. cfile->tlink. Thus a partially initialized cifsFileInfo structure becomes available to other threads that walk through the inode's lock list. One example of such a thread may be an oplock break worker thread that tries to push all cached byte-range locks. This causes NULL-pointer dereference in smb2_push_mandatory_locks() when accessing cfile->tlink: [598428.945633] BUG: kernel NULL pointer dereference, address: 0000000000000038 ... [598428.945749] Workqueue: cifsoplockd cifs_oplock_break [cifs] [598428.945793] RIP: 0010:smb2_push_mandatory_locks+0xd6/0x5a0 [cifs] ... [598428.945834] Call Trace: [598428.945870] ? cifs_revalidate_mapping+0x45/0x90 [cifs] [598428.945901] cifs_oplock_break+0x13d/0x450 [cifs] [598428.945909] process_one_work+0x1db/0x380 [598428.945914] worker_thread+0x4d/0x400 [598428.945921] kthread+0x104/0x140 [598428.945925] ? process_one_work+0x380/0x380 [598428.945931] ? kthread_park+0x80/0x80 [598428.945937] ret_from_fork+0x35/0x40 Fix this by reordering initialization steps of the cifsFileInfo structure: initialize all the fields first and then add the new byte-range lock list to the inode's lock list. Cc: Stable <stable@vger.kernel.org> Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com> Reviewed-by: Aurelien Aptel <aaptel@suse.com> Signed-off-by: Steve French <stfrench@microsoft.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/cifs/file.c7
1 files changed, 4 insertions, 3 deletions
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index f1fe9c44d298..9ae41042fa3d 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -315,9 +315,6 @@ cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
INIT_LIST_HEAD(&fdlocks->locks);
fdlocks->cfile = cfile;
cfile->llist = fdlocks;
- cifs_down_write(&cinode->lock_sem);
- list_add(&fdlocks->llist, &cinode->llist);
- up_write(&cinode->lock_sem);
cfile->count = 1;
cfile->pid = current->tgid;
@@ -342,6 +339,10 @@ cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
oplock = 0;
}
+ cifs_down_write(&cinode->lock_sem);
+ list_add(&fdlocks->llist, &cinode->llist);
+ up_write(&cinode->lock_sem);
+
spin_lock(&tcon->open_file_lock);
if (fid->pending_open->oplock != CIFS_OPLOCK_NO_CHANGE && oplock)
oplock = fid->pending_open->oplock;