From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AB40114A8D for ; Wed, 9 Aug 2023 10:51:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C9222C433C8; Wed, 9 Aug 2023 10:51:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1691578265; bh=24hJtYD6VGbSW98PzYBlom6ABTa9EtnJNpoW7DlJ8GM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1k4Zu3H0A4ABCPFBCnFyTo0WBPpKkXDrSXUDjeuQh2RoSjy3pAF9J+T+exgUF8tDX EzVmjLrr8roI5q+tXNZU2M4e9s9xC/D352jqRdYO+8DayEUyDGsdrCGQT0X+XUYHd+ Ln5F5IERrPIfH7JB3QkWwzdK2An7WFuZc7sea0VE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Roman Gushchin , syzbot+774c29891415ab0fd29d@syzkaller.appspotmail.com, Dmitry Vyukov , Yosry Ahmed , Shakeel Butt , Andrew Morton Subject: [PATCH 6.4 135/165] mm: kmem: fix a NULL pointer dereference in obj_stock_flush_required() Date: Wed, 9 Aug 2023 12:41:06 +0200 Message-ID: <20230809103647.234171510@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230809103642.720851262@linuxfoundation.org> References: <20230809103642.720851262@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Roman Gushchin commit 3b8abb3239530c423c0b97e42af7f7e856e1ee96 upstream. KCSAN found an issue in obj_stock_flush_required(): stock->cached_objcg can be reset between the check and dereference: ================================================================== BUG: KCSAN: data-race in drain_all_stock / drain_obj_stock write to 0xffff888237c2a2f8 of 8 bytes by task 19625 on cpu 0: drain_obj_stock+0x408/0x4e0 mm/memcontrol.c:3306 refill_obj_stock+0x9c/0x1e0 mm/memcontrol.c:3340 obj_cgroup_uncharge+0xe/0x10 mm/memcontrol.c:3408 memcg_slab_free_hook mm/slab.h:587 [inline] __cache_free mm/slab.c:3373 [inline] __do_kmem_cache_free mm/slab.c:3577 [inline] kmem_cache_free+0x105/0x280 mm/slab.c:3602 __d_free fs/dcache.c:298 [inline] dentry_free fs/dcache.c:375 [inline] __dentry_kill+0x422/0x4a0 fs/dcache.c:621 dentry_kill+0x8d/0x1e0 dput+0x118/0x1f0 fs/dcache.c:913 __fput+0x3bf/0x570 fs/file_table.c:329 ____fput+0x15/0x20 fs/file_table.c:349 task_work_run+0x123/0x160 kernel/task_work.c:179 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] exit_to_user_mode_loop+0xcf/0xe0 kernel/entry/common.c:171 exit_to_user_mode_prepare+0x6a/0xa0 kernel/entry/common.c:203 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline] syscall_exit_to_user_mode+0x26/0x140 kernel/entry/common.c:296 do_syscall_64+0x4d/0xc0 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x63/0xcd read to 0xffff888237c2a2f8 of 8 bytes by task 19632 on cpu 1: obj_stock_flush_required mm/memcontrol.c:3319 [inline] drain_all_stock+0x174/0x2a0 mm/memcontrol.c:2361 try_charge_memcg+0x6d0/0xd10 mm/memcontrol.c:2703 try_charge mm/memcontrol.c:2837 [inline] mem_cgroup_charge_skmem+0x51/0x140 mm/memcontrol.c:7290 sock_reserve_memory+0xb1/0x390 net/core/sock.c:1025 sk_setsockopt+0x800/0x1e70 net/core/sock.c:1525 udp_lib_setsockopt+0x99/0x6c0 net/ipv4/udp.c:2692 udp_setsockopt+0x73/0xa0 net/ipv4/udp.c:2817 sock_common_setsockopt+0x61/0x70 net/core/sock.c:3668 __sys_setsockopt+0x1c3/0x230 net/socket.c:2271 __do_sys_setsockopt net/socket.c:2282 [inline] __se_sys_setsockopt net/socket.c:2279 [inline] __x64_sys_setsockopt+0x66/0x80 net/socket.c:2279 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd value changed: 0xffff8881382d52c0 -> 0xffff888138893740 Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 19632 Comm: syz-executor.0 Not tainted 6.3.0-rc2-syzkaller-00387-g534293368afa #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023 Fix it by using READ_ONCE()/WRITE_ONCE() for all accesses to stock->cached_objcg. Link: https://lkml.kernel.org/r/20230502160839.361544-1-roman.gushchin@linux.dev Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API") Signed-off-by: Roman Gushchin Reported-by: syzbot+774c29891415ab0fd29d@syzkaller.appspotmail.com Reported-by: Dmitry Vyukov Link: https://lore.kernel.org/linux-mm/CACT4Y+ZfucZhM60YPphWiCLJr6+SGFhT+jjm8k1P-a_8Kkxsjg@mail.gmail.com/T/#t Reviewed-by: Yosry Ahmed Acked-by: Shakeel Butt Reviewed-by: Dmitry Vyukov Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/memcontrol.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3208,12 +3208,12 @@ void mod_objcg_state(struct obj_cgroup * * accumulating over a page of vmstat data or when pgdat or idx * changes. */ - if (stock->cached_objcg != objcg) { + if (READ_ONCE(stock->cached_objcg) != objcg) { old = drain_obj_stock(stock); obj_cgroup_get(objcg); stock->nr_bytes = atomic_read(&objcg->nr_charged_bytes) ? atomic_xchg(&objcg->nr_charged_bytes, 0) : 0; - stock->cached_objcg = objcg; + WRITE_ONCE(stock->cached_objcg, objcg); stock->cached_pgdat = pgdat; } else if (stock->cached_pgdat != pgdat) { /* Flush the existing cached vmstat data */ @@ -3267,7 +3267,7 @@ static bool consume_obj_stock(struct obj local_lock_irqsave(&memcg_stock.stock_lock, flags); stock = this_cpu_ptr(&memcg_stock); - if (objcg == stock->cached_objcg && stock->nr_bytes >= nr_bytes) { + if (objcg == READ_ONCE(stock->cached_objcg) && stock->nr_bytes >= nr_bytes) { stock->nr_bytes -= nr_bytes; ret = true; } @@ -3279,7 +3279,7 @@ static bool consume_obj_stock(struct obj static struct obj_cgroup *drain_obj_stock(struct memcg_stock_pcp *stock) { - struct obj_cgroup *old = stock->cached_objcg; + struct obj_cgroup *old = READ_ONCE(stock->cached_objcg); if (!old) return NULL; @@ -3332,7 +3332,7 @@ static struct obj_cgroup *drain_obj_stoc stock->cached_pgdat = NULL; } - stock->cached_objcg = NULL; + WRITE_ONCE(stock->cached_objcg, NULL); /* * The `old' objects needs to be released by the caller via * obj_cgroup_put() outside of memcg_stock_pcp::stock_lock. @@ -3343,10 +3343,11 @@ static struct obj_cgroup *drain_obj_stoc static bool obj_stock_flush_required(struct memcg_stock_pcp *stock, struct mem_cgroup *root_memcg) { + struct obj_cgroup *objcg = READ_ONCE(stock->cached_objcg); struct mem_cgroup *memcg; - if (stock->cached_objcg) { - memcg = obj_cgroup_memcg(stock->cached_objcg); + if (objcg) { + memcg = obj_cgroup_memcg(objcg); if (memcg && mem_cgroup_is_descendant(memcg, root_memcg)) return true; } @@ -3365,10 +3366,10 @@ static void refill_obj_stock(struct obj_ local_lock_irqsave(&memcg_stock.stock_lock, flags); stock = this_cpu_ptr(&memcg_stock); - if (stock->cached_objcg != objcg) { /* reset if necessary */ + if (READ_ONCE(stock->cached_objcg) != objcg) { /* reset if necessary */ old = drain_obj_stock(stock); obj_cgroup_get(objcg); - stock->cached_objcg = objcg; + WRITE_ONCE(stock->cached_objcg, objcg); stock->nr_bytes = atomic_read(&objcg->nr_charged_bytes) ? atomic_xchg(&objcg->nr_charged_bytes, 0) : 0; allow_uncharge = true; /* Allow uncharge when objcg changes */