From: Guangshuo Li Date: Fri, 5 Jun 2026 04:30:16 +0000 (+0800) Subject: ksmbd: fix use-after-free in same_client_has_lease() X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=65b655f65c3ca1ab5d598d3832bb0ff531725858;p=thirdparty%2Fkernel%2Flinux.git ksmbd: fix use-after-free in same_client_has_lease() same_client_has_lease() returns an opinfo pointer from ci->m_op_list after dropping ci->m_lock without taking a reference. smb_grant_oplock() then dereferences that pointer in copy_lease() and when checking breaking_cnt. A concurrent close can remove the old lease from ci->m_op_list and drop the last reference before the caller uses the returned pointer, leading to a use-after-free. Take a reference when same_client_has_lease() selects an existing lease, drop any previous match while scanning, and release the returned reference in smb_grant_oplock() after copying the lease state. Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3") Signed-off-by: Guangshuo Li Acked-by: Namjae Jeon Signed-off-by: Steve French --- diff --git a/fs/smb/server/oplock.c b/fs/smb/server/oplock.c index b193dde4810dc..60e7e821c2455 100644 --- a/fs/smb/server/oplock.c +++ b/fs/smb/server/oplock.c @@ -528,7 +528,12 @@ static struct oplock_info *same_client_has_lease(struct ksmbd_inode *ci, ret = compare_guid_key(opinfo, client_guid, lctx->lease_key); if (ret) { + if (!atomic_inc_not_zero(&opinfo->refcount)) + continue; + if (m_opinfo) + opinfo_put(m_opinfo); m_opinfo = opinfo; + /* skip upgrading lease about breaking lease */ if (atomic_read(&opinfo->breaking_cnt)) continue; @@ -1246,6 +1251,7 @@ int smb_grant_oplock(struct ksmbd_work *work, int req_op_level, u64 pid, if (atomic_read(&m_opinfo->breaking_cnt)) opinfo->o_lease->flags = SMB2_LEASE_FLAG_BREAK_IN_PROGRESS_LE; + opinfo_put(m_opinfo); goto out; } }