7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Karl Mehltretter [ Upstream commit 8d01d6b4c17c406f37a9b6edac93dfb858af30d0 ] pin_insert() initializes a pin before adding it under pin_lock. The kill paths read the list heads under RCU without taking that lock. Plain hlist insertion does not publish the earlier initialization to those readers. KCSAN weak-memory checking reported acct_on() callback initialization racing with pin_kill() after the superblock-list publication. The corresponding LKMM model permits the stale read with plain publication; the RCU release/acquire pair forbids it. Use the RCU hlist add and dereference helpers for both pin lists. Fixes: 2798d4ce6160 ("acct: get rid of acct_lock for acct->count") Cc: stable@vger.kernel.org Signed-off-by: Karl Mehltretter Link: https://patch.msgid.link/20260903002100.34822-1-kmehltretter@gmail.com Reviewed-by: Jan Kara Signed-off-by: Christian Brauner (Amutable) Signed-off-by: Sasha Levin --- fs/fs_pin.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/fs/fs_pin.c b/fs/fs_pin.c index 47ef3c71ce907..1a508f2167e0a 100644 --- a/fs/fs_pin.c +++ b/fs/fs_pin.c @@ -1,5 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 #include +#include #include #include #include "internal.h" @@ -22,8 +23,8 @@ void pin_remove(struct fs_pin *pin) void pin_insert(struct fs_pin *pin, struct vfsmount *m) { spin_lock(&pin_lock); - hlist_add_head(&pin->s_list, &m->mnt_sb->s_pins); - hlist_add_head(&pin->m_list, &real_mount(m)->mnt_pins); + hlist_add_head_rcu(&pin->s_list, &m->mnt_sb->s_pins); + hlist_add_head_rcu(&pin->m_list, &real_mount(m)->mnt_pins); spin_unlock(&pin_lock); } @@ -73,7 +74,7 @@ void mnt_pin_kill(struct mount *m) while (1) { struct hlist_node *p; rcu_read_lock(); - p = READ_ONCE(m->mnt_pins.first); + p = rcu_dereference(hlist_first_rcu(&m->mnt_pins)); if (!p) { rcu_read_unlock(); break; @@ -87,7 +88,7 @@ void group_pin_kill(struct hlist_head *p) while (1) { struct hlist_node *q; rcu_read_lock(); - q = READ_ONCE(p->first); + q = rcu_dereference(hlist_first_rcu(p)); if (!q) { rcu_read_unlock(); break; -- 2.53.0