From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 7FEE73B3BFE; Fri, 9 Oct 2026 14:35:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791556504; cv=none; b=Xycb2Dsi9S38yBx4brvWe0yYYOXFiEXv+XL9bwBBgO0B58407ufpVlRzIAyMF9IWRiZkXIrJekmkAIVScy5MAMrA68MUIPYvNGoHOuls3D6quVGtDjGrIDtwVNTUqZQlPS8H0mjQjXy3ukqjRceFc7mNmbf20vusGb9nRC/oQlg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791556504; c=relaxed/simple; bh=AsytZDle8AT/HOImC0Qt3B04a2tPtGUtwYCvoUTrZV0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=IRqmxu+MzZ9OAPle2AIDe3Q1hKOguDIJO3Yrgr5vMdi7FHiKX4W1R9eu3qPTNYmVR9Q9kq9tw8+sUk0SF8imsrEQtA1ZHlHxvu72gNQ83BEBCimR4NnEK8YZsNXyR6TjST5ntb8T48hNtkOwfNAZ8MzijaHwI+lngtSBa2mVkI4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Ql4766iR; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Ql4766iR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE3D91F00898; Fri, 9 Oct 2026 14:35:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1791556502; bh=n7V+25ifSmnjuhUbFCqJzU7cdWBuYK6rgVu2z80ibj8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Ql4766iRqnzgF+qoss59ZKZmVdaqP+LhfiAzg8g21punGyX2lmFRzzBV6qSNf+SF7 q+1AwFF+piqgA7fl6lERSM7mQxYj4/Pvfv6j2KWZKWMHO1/iTJGmXkk6zUCQgwxrHP 7sq0e7Q84etUHRNka263pJZaeBEEzpreC+fgyVrw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable , Peiyang He , Carlos Llamas Subject: [PATCH 7.2 192/428] binderfs: fix UAF write in binder_add_device Date: Fri, 9 Oct 2026 16:08:49 +0200 Message-ID: <20261009140950.358946353@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261009140946.008206689@linuxfoundation.org> References: <20261009140946.008206689@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peiyang He commit 30d15f44a9e513ec2f257fdf192d9d1fa5af0799 upstream. binderfs_binder_device_create() publishes the new dentry with d_make_persistent() and then calls simple_done_creating(), which drops the parent directory lock and the creator's dentry reference. It then calls binder_add_device() to register the device in the global binder_devices list. After simple_done_creating() releases the parent directory lock, a concurrent unlinkat() can remove the new device entry. Dropping the creator's dentry reference can then trigger binderfs_evict_inode(), freeing the device. binder_add_device() later accesses the freed object, causing UAF write. Found by a modified Syzkaller: BUG: KASAN: slab-use-after-free in hlist_add_head include/linux/list.h:1073 [inline] BUG: KASAN: slab-use-after-free in binder_add_device+0xa9/0xc0 drivers/android/binder.c:7068 Write of size 8 at addr ffff88805b340c00 by task syz.1.532/11389 CPU: 0 UID: 0 PID: 11389 Comm: syz.1.532 Not tainted 7.2.0 #4 PREEMPT(full) Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x10e/0x1f0 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xf7/0x600 mm/kasan/report.c:482 kasan_report+0xe4/0x120 mm/kasan/report.c:595 hlist_add_head include/linux/list.h:1073 [inline] binder_add_device+0xa9/0xc0 drivers/android/binder.c:7068 binderfs_binder_device_create.isra.0+0x724/0x990 drivers/android/binderfs.c:196 binder_ctl_ioctl+0x186/0x1b0 drivers/android/binderfs.c:241 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x116/0x800 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7ff9027a833d Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ff903674018 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007ff902a35fa0 RCX: 00007ff9027a833d RDX: 0000200000000500 RSI: 00000000c1086201 RDI: 0000000000000004 RBP: 00007ff902850733 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ff902a36038 R14: 00007ff902a35fa0 R15: 00007ffd7166bfa0 Allocated by task 11389: kasan_save_stack+0x33/0x60 mm/kasan/common.c:57 kasan_save_track+0x14/0x30 mm/kasan/common.c:78 poison_kmalloc_redzone mm/kasan/common.c:398 [inline] __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415 kasan_kmalloc include/linux/kasan.h:263 [inline] __kmalloc_cache_noprof+0x2e4/0x6f0 mm/slub.c:5489 _kmalloc_noprof include/linux/slab.h:988 [inline] _kzalloc_noprof include/linux/slab.h:1309 [inline] binderfs_binder_device_create.isra.0+0x17a/0x990 drivers/android/binderfs.c:148 binder_ctl_ioctl+0x186/0x1b0 drivers/android/binderfs.c:241 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x116/0x800 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 11389: kasan_save_stack+0x33/0x60 mm/kasan/common.c:57 kasan_save_track+0x14/0x30 mm/kasan/common.c:78 kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:253 [inline] __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:2677 [inline] slab_free mm/slub.c:6377 [inline] kfree+0x2fc/0x6e0 mm/slub.c:6692 binderfs_evict_inode+0x1e8/0x260 drivers/android/binderfs.c:268 evict+0x3c2/0xad0 fs/inode.c:825 iput_final fs/inode.c:2019 [inline] iput fs/inode.c:2068 [inline] iput+0x79a/0xd30 fs/inode.c:2031 dentry_unlink_inode+0x27f/0x460 fs/dcache.c:479 dentry_kill+0x25d/0xc20 fs/dcache.c:826 finish_dput fs/dcache.c:1001 [inline] dput.part.0+0xce/0x230 fs/dcache.c:1042 dput+0x1f/0x30 fs/dcache.c:1037 end_dirop+0x7d/0xa0 fs/namei.c:2956 binderfs_binder_device_create.isra.0+0x71c/0x990 drivers/android/binderfs.c:194 binder_ctl_ioctl+0x186/0x1b0 drivers/android/binderfs.c:241 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x116/0x800 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff88805b340c00 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 0 bytes inside of freed 512-byte region [ffff88805b340c00, ffff88805b340e00) Fix by calling binder_add_device() before d_make_persistent(), while the parent directory lock is still held and the dentry cannot be discarded. Cc: stable Fixes: b89aa544821d ("convert binderfs") Signed-off-by: Peiyang He Assisted-by: Codex:gpt-5.5 Acked-by: Carlos Llamas Link: https://patch.msgid.link/F6EF5FB778E87C98+20260913085645.1639558-1-peiyang_he@smail.nju.edu.cn Signed-off-by: Greg Kroah-Hartman --- drivers/android/binderfs.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- a/drivers/android/binderfs.c +++ b/drivers/android/binderfs.c @@ -189,12 +189,11 @@ static int binderfs_binder_device_create goto err; } inode->i_private = device; + binder_add_device(device); d_make_persistent(dentry, inode); fsnotify_create(root->d_inode, dentry); simple_done_creating(dentry); - binder_add_device(device); - return 0; err: