From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kylie.crudebyte.com (kylie.crudebyte.com [5.189.157.229]) (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 B3F3D267701; Thu, 13 Mar 2025 13:29:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=5.189.157.229 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741872589; cv=none; b=WWPm66freWgMxIEjg3nRR8WFb///mc8nETgtEzKG3P5y4m5JqC9er8r1uuaXST006kywRVt74iBqk3qt/GdStcBc6/0+gfui0pqk1B+2ycf0/f67govVA9iMWdcv89ZTSkkDfcHLHM1wTEgnUPFwlvJw/0+D6ySiIWCIvaiiaFE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741872589; c=relaxed/simple; bh=SWcBEiDC6xd/PujYJvpj52/K9l9YFvwj3Xw6G6hAUuw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=MFwaTTVD265Dxq5p4rOB3AkjMT64rqLKhLpDG634QLR/Q+nix/qTHJ7Nz6jiuHEoOxzp3zhHNYL6BbhuPOZIDxUsWtfphMmmagMRBbMmcmLX5pEmuNxbD3tQE0BiTj9ze9X3lcBHgCzOT8Ul9DU3O7DqJQvZPpdqkPyjTZSeqfE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=crudebyte.com; spf=pass smtp.mailfrom=crudebyte.com; dkim=pass (4096-bit key) header.d=crudebyte.com header.i=@crudebyte.com header.b=fQbnOpSb; arc=none smtp.client-ip=5.189.157.229 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=crudebyte.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=crudebyte.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (4096-bit key) header.d=crudebyte.com header.i=@crudebyte.com header.b="fQbnOpSb" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=crudebyte.com; s=kylie; h=Content-Type:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Content-ID:Content-Description; bh=ITLasxmQDerXuSjwxhFppjXCgBmI89lbRmvF9Iy20jA=; b=fQbnOpSbDJIJdf3sQaILolccPG DQWcJ4ixHQF2Kts21kpaZ64J6HoOt0b/6kEwDpofSKO9VBIcTVZRFASmIImcSQ5Vp7NgGFxPNDgKa Qu+UD+6qVeVbg42s+Rm2o/LBPu95oyy/x6yic9ETZhWh+mxoft7vEqaN8f93kX7DsqG6bBXI89NKt 5wddGm4BYPbOlP0Q910pGiRRgXxFiW1tdyectSqVfpWVx9Ura3YcwTE8C6vLGLBlfGCEaclwCXhjP On39TH1+c8xdIsdp68i/Rl8caM7n8yU9BWRPtXDWhCKxYhXPou8ZcYjBnXh4E4/Vt9wMSgCgTjBBG dON0V5WfUNQE7qCBMN6vaG4sHaBWkPpw+belxDr7nQwBshraDyf5yLa9QrRiTcUtd7KDMo8rGDoOD pJPPdWTgeZMkroEO/AJJ3JuFHaVT0gPM3YUOV+G+xPFyjK4+5hvL8ojs8E3gLyiv8BpI0wmz8U65x FFyHNlLbjJl2YhOhBkbIpcpRq9TM9TvTcgVgQaIxN5DhN1At9Wg76dpSQ0DaDPuNpJFf+ECuOvs8D b81ZvExbeezTTh32CFm4WjXSYAgx5CMQRoPQgUHWwy0Io8VmUhTB/OQ838EXZI8FPaEMy0zGE3vfg cp/fQn7qK5BhAImvwwIOWGsLaprnsXNLaT6F6XqB8=; From: Christian Schoenebeck To: Dominique Martinet Cc: Eric Van Hensbergen , Latchesar Ionkov , v9fs@lists.linux.dev, linux-kernel@vger.kernel.org, syzbot Subject: Re: [PATCH] fs/9p: fix NULL pointer dereference on mkdir Date: Thu, 13 Mar 2025 14:29:42 +0100 Message-ID: <4597443.VRNSQfLuZI@silver> In-Reply-To: References: Precedence: bulk X-Mailing-List: v9fs@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" On Thursday, March 13, 2025 1:59:32 PM CET Christian Schoenebeck wrote: > When a 9p tree was mounted with option 'posixacl', parent directory had a > default ACL set for its subdirectories, e.g.: > > setfacl -m default:group:simpsons:rwx parentdir > > then creating a subdirectory crashed 9p client, as v9fs_fid_add() call in > function v9fs_vfs_mkdir_dotl() sets the passed 'fid' pointer to NULL > (since dafbe689736) even though the subsequent v9fs_set_create_acl() call > expects a valid non-NULL 'fid' pointer: > > [ 37.273191] BUG: kernel NULL pointer dereference, address: 0000000000000000 > ... > [ 37.322338] Call Trace: > [ 37.323043] > [ 37.323621] ? __die+0x1f/0x60 > [ 37.324448] ? page_fault_oops+0x158/0x470 > [ 37.325532] ? search_module_extables+0x4a/0x80 > [ 37.326742] ? p9_client_walk+0x1c/0x2c0 [9pnet] > [ 37.328006] ? search_bpf_extables+0x5b/0x80 > [ 37.329142] ? exc_page_fault+0x72/0x190 > [ 37.330196] ? asm_exc_page_fault+0x22/0x30 > [ 37.331330] ? p9_client_walk+0x1c/0x2c0 [9pnet] > [ 37.332562] ? v9fs_fid_xattr_get+0x59/0x120 [9p] > [ 37.333824] v9fs_fid_xattr_set+0x6f/0x130 [9p] > [ 37.335077] v9fs_set_acl+0x82/0xc0 [9p] > [ 37.336112] v9fs_set_create_acl+0x41/0x60 [9p] > [ 37.337326] v9fs_vfs_mkdir_dotl+0x20d/0x2e0 [9p] > [ 37.338590] vfs_mkdir+0x192/0x250 > [ 37.339535] do_mkdirat+0x135/0x160 > [ 37.340465] __x64_sys_mkdir+0x42/0x60 > [ 37.341455] do_syscall_64+0x4b/0x110 > [ 37.342447] entry_SYSCALL_64_after_hwframe+0x76/0x7e Oops, forgot to decode the trace back: [ 37.322338] Call Trace: [ 37.323043] [ 37.323621] ? __die (arch/x86/kernel/dumpstack.c:421 arch/x86/kernel/dumpstack.c:434) [ 37.324448] ? page_fault_oops (arch/x86/mm/fault.c:714) [ 37.325532] ? search_module_extables (kernel/module/main.c:3733) [ 37.326742] ? p9_client_walk (net/9p/client.c:1165) 9pnet [ 37.328006] ? search_bpf_extables (kernel/bpf/core.c:804) [ 37.329142] ? exc_page_fault (./arch/x86/include/asm/paravirt.h:686 arch/x86/mm/fault.c:1488 arch/x86/mm/fault.c:1538) [ 37.330196] ? asm_exc_page_fault (./arch/x86/include/asm/idtentry.h:574) [ 37.331330] ? p9_client_walk (net/9p/client.c:1165) 9pnet [ 37.332562] ? v9fs_fid_xattr_get (fs/9p/xattr.c:30) 9p [ 37.333824] v9fs_fid_xattr_set (fs/9p/fid.h:23 fs/9p/xattr.c:121) 9p [ 37.335077] v9fs_set_acl (fs/9p/acl.c:276) 9p [ 37.336112] v9fs_set_create_acl (fs/9p/acl.c:307) 9p [ 37.337326] v9fs_vfs_mkdir_dotl (fs/9p/vfs_inode_dotl.c:411) 9p [ 37.338590] vfs_mkdir (fs/namei.c:4313) [ 37.339535] do_mkdirat (fs/namei.c:4336) [ 37.340465] __x64_sys_mkdir (fs/namei.c:4354) [ 37.341455] do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83) [ 37.342447] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) Dominique, do you want me to send a v2 or would you update the commit log on your end? /Christian > Fix this by simply swapping the sequence of these two calls in > v9fs_vfs_mkdir_dotl(), i.e. calling v9fs_set_create_acl() before > v9fs_fid_add(). > > Fixes: dafbe689736 ('9p fid refcount: cleanup p9_fid_put calls') > Reported-by: syzbot+5b667f9a1fee4ba3775a@syzkaller.appspotmail.com > Signed-off-by: Christian Schoenebeck > --- > fs/9p/vfs_inode_dotl.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c > index 143ac03b7425..3397939fd2d5 100644 > --- a/fs/9p/vfs_inode_dotl.c > +++ b/fs/9p/vfs_inode_dotl.c > @@ -407,8 +407,8 @@ static int v9fs_vfs_mkdir_dotl(struct mnt_idmap *idmap, > err); > goto error; > } > - v9fs_fid_add(dentry, &fid); > v9fs_set_create_acl(inode, fid, dacl, pacl); > + v9fs_fid_add(dentry, &fid); > d_instantiate(dentry, inode); > err = 0; > inc_nlink(dir); >