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smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=mEYFvZg7; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="mEYFvZg7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0691CC4AF09; Thu, 18 Jul 2024 11:09:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1721300948; bh=Hi6+PXjlyeovTHQCMrMLw0CwZB4LvaETQJ3QzsgUfO8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mEYFvZg7kvRmLB/LOXJn1qqSA4nL8dLMVSOAco0ZhQdjCaDlGP4P53gW8yXa1m7TD qTQ8qt8e6RyfQu52erOphvgADnHQpgF4bsFbjyb4yE8ByKWRdOZnzaspku1cyqczfv qa/RV4LHRMRA1LgH7F1/q7H3lBlHVo5dqgNKCpjc= Date: Thu, 18 Jul 2024 13:09:05 +0200 From: Greg KH To: Marco Elver Cc: syzbot , linux-kernel@vger.kernel.org, rafael@kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [kernel?] KCSAN: data-race in kobject_put / kobject_uevent_env (2) Message-ID: <2024071845-breach-dripping-a1e5@gregkh> References: <000000000000381fbb061d81bd85@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Jul 18, 2024 at 12:38:05PM +0200, Marco Elver wrote: > On Thu, 18 Jul 2024 at 10:55, syzbot > wrote: > > > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: d67978318827 Merge tag 'x86_cpu_for_v6.11_rc1' of git://gi.. > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=11af145e980000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=ca8f4e92a17047ec > > dashboard link: https://syzkaller.appspot.com/bug?extid=0ac8e4da6d5cfcc7743e > > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 > > > > Unfortunately, I don't have any reproducer for this issue yet. > > > > Downloadable assets: > > disk image: https://storage.googleapis.com/syzbot-assets/1f219d0a9994/disk-d6797831.raw.xz > > vmlinux: https://storage.googleapis.com/syzbot-assets/91aed26b830f/vmlinux-d6797831.xz > > kernel image: https://storage.googleapis.com/syzbot-assets/c7e753e56950/bzImage-d6797831.xz > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+0ac8e4da6d5cfcc7743e@syzkaller.appspotmail.com > > > > llcp: llcp_sock_recvmsg: Recv datagram failed state 3 -6 0 > > ================================================================== > > BUG: KCSAN: data-race in kobject_put / kobject_uevent_env > > > > read-write to 0xffff888139ddec54 of 1 bytes by task 22621 on cpu 0: > > kobject_uevent_env+0x4e/0x550 lib/kobject_uevent.c:476 > > kobject_uevent+0x1c/0x30 lib/kobject_uevent.c:641 > > device_del+0x6fa/0x780 drivers/base/core.c:3886 > > nfc_unregister_device+0x114/0x130 net/nfc/core.c:1183 > > nci_unregister_device+0x14c/0x160 net/nfc/nci/core.c:1312 > > virtual_ncidev_close+0x30/0x50 drivers/nfc/virtual_ncidev.c:172 > > __fput+0x192/0x6f0 fs/file_table.c:422 > > ____fput+0x15/0x20 fs/file_table.c:450 > > task_work_run+0x13a/0x1a0 kernel/task_work.c:180 > > resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] > > exit_to_user_mode_loop kernel/entry/common.c:114 [inline] > > exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline] > > __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] > > syscall_exit_to_user_mode+0xbe/0x130 kernel/entry/common.c:218 > > do_syscall_64+0xd6/0x1c0 arch/x86/entry/common.c:89 > > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > > > read to 0xffff888139ddec54 of 1 bytes by task 22615 on cpu 1: > > kobject_put+0x25/0x180 lib/kobject.c:733 > > put_device+0x1f/0x30 drivers/base/core.c:3787 > > nfc_put_device net/nfc/nfc.h:103 [inline] > > nfc_llcp_local_put+0x87/0xb0 net/nfc/llcp_core.c:196 > > nfc_llcp_sock_free net/nfc/llcp_sock.c:1021 [inline] > > llcp_sock_destruct+0x14d/0x1a0 net/nfc/llcp_sock.c:966 > > __sk_destruct+0x3d/0x440 net/core/sock.c:2175 > > sk_destruct net/core/sock.c:2223 [inline] > > __sk_free+0x284/0x2d0 net/core/sock.c:2234 > > sk_free+0x39/0x70 net/core/sock.c:2245 > > sock_put include/net/sock.h:1879 [inline] > > llcp_sock_release+0x38f/0x3d0 net/nfc/llcp_sock.c:646 > > __sock_release net/socket.c:659 [inline] > > sock_close+0x68/0x150 net/socket.c:1421 > > __fput+0x192/0x6f0 fs/file_table.c:422 > > ____fput+0x15/0x20 fs/file_table.c:450 > > task_work_run+0x13a/0x1a0 kernel/task_work.c:180 > > resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] > > exit_to_user_mode_loop kernel/entry/common.c:114 [inline] > > exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline] > > __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] > > syscall_exit_to_user_mode+0xbe/0x130 kernel/entry/common.c:218 > > do_syscall_64+0xd6/0x1c0 arch/x86/entry/common.c:89 > > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > > > value changed: 0x07 -> 0x0d > > > > Reported by Kernel Concurrency Sanitizer on: > > CPU: 1 PID: 22615 Comm: syz.0.6322 Tainted: G W 6.10.0-syzkaller-01155-gd67978318827 #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024 > > ================================================================== > > The two racing accesses here (on bitfield variables > kobj->state_remove_uevent_sent, kobj->state_initialized) are in the > same bitfield. There's no guarantee (by the compiler) that while the > bitfield is being updated the bit at kobj->state_initialized will > remain non-zero, and therefore the WARN in kobject_put() could be > triggered. This appears benign, unless of course someone set > panic_on_warn. > > More generally, if the bitfield is updated concurrently, it's very > likely that one of the updates would be lost. > > Just my initial observation. Thanks for the review, I'll try to carve out some time next week to knock up a patch for this... greg k-h