From 1dfd062caa165ec9d7ee0823087930f3ab8a6294 Mon Sep 17 00:00:00 2001 From: Namjae Jeon Date: Sat, 7 Mar 2026 11:32:31 +0900 Subject: ksmbd: fix use-after-free by using call_rcu() for oplock_info ksmbd currently frees oplock_info immediately using kfree(), even though it is accessed under RCU read-side critical sections in places like opinfo_get() and proc_show_files(). Since there is no RCU grace period delay between nullifying the pointer and freeing the memory, a reader can still access oplock_info structure after it has been freed. This can leads to a use-after-free especially in opinfo_get() where atomic_inc_not_zero() is called on already freed memory. Fix this by switching to deferred freeing using call_rcu(). Fixes: 18b4fac5ef17 ("ksmbd: fix use-after-free in smb_break_all_levII_oplock()") Cc: stable@vger.kernel.org Signed-off-by: Namjae Jeon Signed-off-by: Steve French --- fs/smb/server/oplock.c | 29 +++++++++++++++++++++-------- fs/smb/server/oplock.h | 5 +++-- 2 files changed, 24 insertions(+), 10 deletions(-) (limited to 'fs') diff --git a/fs/smb/server/oplock.c b/fs/smb/server/oplock.c index 09d9878db9cb..8c9aa17384f3 100644 --- a/fs/smb/server/oplock.c +++ b/fs/smb/server/oplock.c @@ -120,7 +120,7 @@ static void free_lease(struct oplock_info *opinfo) kfree(lease); } -static void free_opinfo(struct oplock_info *opinfo) +static void __free_opinfo(struct oplock_info *opinfo) { if (opinfo->is_lease) free_lease(opinfo); @@ -129,6 +129,18 @@ static void free_opinfo(struct oplock_info *opinfo) kfree(opinfo); } +static void free_opinfo_rcu(struct rcu_head *rcu) +{ + struct oplock_info *opinfo = container_of(rcu, struct oplock_info, rcu); + + __free_opinfo(opinfo); +} + +static void free_opinfo(struct oplock_info *opinfo) +{ + call_rcu(&opinfo->rcu, free_opinfo_rcu); +} + struct oplock_info *opinfo_get(struct ksmbd_file *fp) { struct oplock_info *opinfo; @@ -176,9 +188,9 @@ void opinfo_put(struct oplock_info *opinfo) free_opinfo(opinfo); } -static void opinfo_add(struct oplock_info *opinfo) +static void opinfo_add(struct oplock_info *opinfo, struct ksmbd_file *fp) { - struct ksmbd_inode *ci = opinfo->o_fp->f_ci; + struct ksmbd_inode *ci = fp->f_ci; down_write(&ci->m_lock); list_add(&opinfo->op_entry, &ci->m_op_list); @@ -1277,20 +1289,21 @@ set_lev: set_oplock_level(opinfo, req_op_level, lctx); out: - rcu_assign_pointer(fp->f_opinfo, opinfo); - opinfo->o_fp = fp; - opinfo_count_inc(fp); - opinfo_add(opinfo); + opinfo_add(opinfo, fp); + if (opinfo->is_lease) { err = add_lease_global_list(opinfo); if (err) goto err_out; } + rcu_assign_pointer(fp->f_opinfo, opinfo); + opinfo->o_fp = fp; + return 0; err_out: - free_opinfo(opinfo); + __free_opinfo(opinfo); return err; } diff --git a/fs/smb/server/oplock.h b/fs/smb/server/oplock.h index 9a56eaadd0dd..921e3199e4df 100644 --- a/fs/smb/server/oplock.h +++ b/fs/smb/server/oplock.h @@ -69,8 +69,9 @@ struct oplock_info { struct lease *o_lease; struct list_head op_entry; struct list_head lease_entry; - wait_queue_head_t oplock_q; /* Other server threads */ - wait_queue_head_t oplock_brk; /* oplock breaking wait */ + wait_queue_head_t oplock_q; /* Other server threads */ + wait_queue_head_t oplock_brk; /* oplock breaking wait */ + struct rcu_head rcu; }; struct lease_break_info { -- cgit v1.2.3