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ksmbd: fix NULL-deref of opinfo->conn in oplock/lease break notifiers

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smb2_oplock_break_noti() and smb2_lease_break_noti() read opinfo->conn
into a local with neither READ_ONCE() nor a NULL check.  Both run from
oplock_break() after opinfo_get_list() has dropped ci->m_lock, so a
concurrent SMB2 LOGOFF (session_fd_check()) can set op->conn = NULL
under ci->m_lock within that window.  ksmbd_conn_r_count_inc(conn) then
writes through NULL at offset 0xc4 -- a remotely triggerable oops.

Guard both reads the way compare_guid_key() already does: read
opinfo->conn with READ_ONCE() and return early if it is NULL, before
allocating the work struct so nothing leaks.  A NULL conn means the
client is gone and the break is moot, so return 0; oplock_break() treats
that as success and runs the normal teardown.

Fixes: c8efcc7861 ("ksmbd: add support for durable handles v1/v2")
Assisted-by: Henry (Claude):claude-opus-4
Signed-off-by: Gil Portnoy <dddhkts1@gmail.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Gil Portnoy 2026-05-28 00:00:00 +00:00 committed by Steve French
parent e43ffb69e0
commit b003086d76
1 changed files with 12 additions and 3 deletions
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15
fs/smb/server/oplock.c
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@ -711,11 +711,16 @@ static void __smb2_oplock_break_noti(struct work_struct *wk)
*/
static int smb2_oplock_break_noti(struct oplock_info *opinfo)
{
struct ksmbd_conn *conn = opinfo->conn;
struct ksmbd_conn *conn;
struct oplock_break_info *br_info;
int ret = 0;
struct ksmbd_work *work = ksmbd_alloc_work_struct();
struct ksmbd_work *work;
conn = READ_ONCE(opinfo->conn);
if (!conn)
return 0;
work = ksmbd_alloc_work_struct();
if (!work)
return -ENOMEM;
@ -815,11 +820,15 @@ static void __smb2_lease_break_noti(struct work_struct *wk)
*/
static int smb2_lease_break_noti(struct oplock_info *opinfo)
{
struct ksmbd_conn *conn = opinfo->conn;
struct ksmbd_conn *conn;
struct ksmbd_work *work;
struct lease_break_info *br_info;
struct lease *lease = opinfo->o_lease;
conn = READ_ONCE(opinfo->conn);
if (!conn)
return 0;
work = ksmbd_alloc_work_struct();
if (!work)
return -ENOMEM;