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Wed, 26 Feb 2020 20:06:46 +0000 Received: by smtp412.mail.ne1.yahoo.com (Oath Hermes SMTP Server) with ESMTPA ID 6c4cfb89c46ba96d6c56e874a1660e0e; Wed, 26 Feb 2020 20:06:40 +0000 (UTC) Subject: Re: suspicious RCU usage from smack code To: John Garry , "jmorris@namei.org" , "serge@hallyn.com" , linux-security-module@vger.kernel.org Cc: Anders Roxell , Casey Schaufler References: <9d97e54f-a7d3-30fa-de4c-ae8d70dee087@huawei.com> From: Casey Schaufler Autocrypt: addr=casey@schaufler-ca.com; keydata= mQINBFzV9HABEAC/mmv3jeJyF7lR7QhILYg1+PeBLIMZv7KCzBSc/4ZZipoWdmr77Lel/RxQ 1PrNx0UaM5r6Hj9lJmJ9eg4s/TUBSP67mTx+tsZ1RhG78/WFf9aBe8MSXxY5cu7IUwo0J/CG vdSqACKyYPV5eoTJmnMxalu8/oVUHyPnKF3eMGgE0mKOFBUMsb2pLS/enE4QyxhcZ26jeeS6 3BaqDl1aTXGowM5BHyn7s9LEU38x/y2ffdqBjd3au2YOlvZ+XUkzoclSVfSR29bomZVVyhMB h1jTmX4Ac9QjpwsxihT8KNGvOM5CeCjQyWcW/g8LfWTzOVF9lzbx6IfEZDDoDem4+ZiPsAXC SWKBKil3npdbgb8MARPes2DpuhVm8yfkJEQQmuLYv8GPiJbwHQVLZGQAPBZSAc7IidD2zbf9 XAw1/SJGe1poxOMfuSBsfKxv9ba2i8hUR+PH7gWwkMQaQ97B1yXYxVEkpG8Y4MfE5Vd3bjJU kvQ/tOBUCw5zwyIRC9+7zr1zYi/3hk+OG8OryZ5kpILBNCo+aePeAJ44znrySarUqS69tuXd a3lMPHUJJpUpIwSKQ5UuYYkWlWwENEWSefpakFAIwY4YIBkzoJ/t+XJHE1HTaJnRk6SWpeDf CreF3+LouP4njyeLEjVIMzaEpwROsw++BX5i5vTXJB+4UApTAQARAQABtChDYXNleSBTY2hh dWZsZXIgPGNhc2V5QHNjaGF1Zmxlci1jYS5jb20+iQJUBBMBCAA+FiEEC+9tH1YyUwIQzUIe OKUVfIxDyBEFAlzV9HACGwMFCRLMAwAFCwkIBwIGFQoJCAsCBBYCAwECHgECF4AACgkQOKUV fIxDyBG6ag/6AiRl8yof47YOEVHlrmewbpnlBTaYNfJ5cZflNRKRX6t4bp1B2YV1whlDTpiL vNOwFkh+ZE0eI5M4x8Gw2Oiok+4Q5liA9PHTozQYF+Ia+qdL5EehfbLGoEBqklpGvG3h8JsO 7SvONJuFDgvab/U/UriDYycJwzwKZuhVtK9EMpnTtUDyP3DY+Q8h7MWsniNBLVXnh4yBIEJg SSgDn3COpZoFTPGKE+rIzioo/GJe8CTa2g+ZggJiY/myWTS3quG0FMvwvNYvZ4I2g6uxSl7n bZVqAZgqwoTAv1HSXIAn9muwZUJL03qo25PFi2gQmX15BgJKQcV5RL0GHFHRThDS3IyadOgK P2j78P8SddTN73EmsG5OoyzwZAxXfck9A512BfVESqapHurRu2qvMoUkQaW/2yCeRQwGTsFj /rr0lnOBkyC6wCmPSKXe3dT2mnD5KnCkjn7KxLqexKt4itGjJz4/ynD/qh+gL7IPbifrQtVH JI7cr0fI6Tl8V6efurk5RjtELsAlSR6fKV7hClfeDEgLpigHXGyVOsynXLr59uE+g/+InVic jKueTq7LzFd0BiduXGO5HbGyRKw4MG5DNQvC//85EWmFUnDlD3WHz7Hicg95D+2IjD2ZVXJy x3LTfKWdC8bU8am1fi+d6tVEFAe/KbUfe+stXkgmfB7pxqW5Ag0EXNX0cAEQAPIEYtPebJzT wHpKLu1/j4jQcke06Kmu5RNuj1pEje7kX5IKzQSs+CPH0NbSNGvrA4dNGcuDUTNHgb5Be9hF zVqRCEvF2j7BFbrGe9jqMBWHuWheQM8RRoa2UMwQ704mRvKr4sNPh01nKT52ASbWpBPYG3/t WbYaqfgtRmCxBnqdOx5mBJIBh9Q38i63DjQgdNcsTx2qS7HFuFyNef5LCf3jogcbmZGxG/b7 yF4OwmGsVc8ufvlKo5A9Wm+tnRjLr/9Mn9vl5Xa/tQDoPxz26+aWz7j1in7UFzAarcvqzsdM Em6S7uT+qy5jcqyuipuenDKYF/yNOVSNnsiFyQTFqCPCpFihOnuaWqfmdeUOQHCSo8fD4aRF emsuxqcsq0Jp2ODq73DOTsdFxX2ESXYoFt3Oy7QmIxeEgiHBzdKU2bruIB5OVaZ4zWF+jusM Uh+jh+44w9DZkDNjxRAA5CxPlmBIn1OOYt1tsphrHg1cH1fDLK/pDjsJZkiH8EIjhckOtGSb aoUUMMJ85nVhN1EbU/A3DkWCVFEA//Vu1+BckbSbJKE7Hl6WdW19BXOZ7v3jo1q6lWwcFYth esJfk3ZPPJXuBokrFH8kqnEQ9W2QgrjDX3et2WwZFLOoOCItWxT0/1QO4ikcef/E7HXQf/ij Dxf9HG2o5hOlMIAkJq/uLNMvABEBAAGJAjwEGAEIACYWIQQL720fVjJTAhDNQh44pRV8jEPI EQUCXNX0cAIbDAUJEswDAAAKCRA4pRV8jEPIEWkzEACKFUnpp+wIVHpckMfBqN8BE5dUbWJc GyQ7wXWajLtlPdw1nNw0Wrv+ob2RCT7qQlUo6GRLcvj9Fn5tR4hBvR6D3m8aR0AGHbcC62cq I7LjaSDP5j/em4oVL2SMgNTrXgE2w33JMGjAx9oBzkxmKUqprhJomPwmfDHMJ0t7y39Da724 oLPTkQDpJL1kuraM9TC5NyLe1+MyIxqM/8NujoJbWeQUgGjn9uxQAil7o/xSCjrWCP3kZDID vd5ZaHpdl8e1mTExQoKr4EWgaMjmD/a3hZ/j3KfTVNpM2cLfD/QwTMaC2fkK8ExMsz+rUl1H icmcmpptCwOSgwSpPY1Zfio6HvEJp7gmDwMgozMfwQuT9oxyFTxn1X3rn1IoYQF3P8gsziY5 qtTxy2RrgqQFm/hr8gM78RhP54UPltIE96VywviFzDZehMvuwzW//fxysIoK97Y/KBZZOQs+ /T+Bw80Pwk/dqQ8UmIt2ffHEgwCTbkSm711BejapWCfklxkMZDp16mkxSt2qZovboVjXnfuq wQ1QL4o4t1hviM7LyoflsCLnQFJh6RSBhBpKQinMJl/z0A6NYDkQi6vEGMDBWX/M2vk9Jvwa v0cEBfY3Z5oFgkh7BUORsu1V+Hn0fR/Lqq/Pyq+nTR26WzGDkolLsDr3IH0TiAVH5ZuPxyz6 abzjfg== Message-ID: Date: Wed, 26 Feb 2020 12:06:39 -0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <9d97e54f-a7d3-30fa-de4c-ae8d70dee087@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US X-Mailer: WebService/1.1.15302 hermes Apache-HttpAsyncClient/4.1.4 (Java/1.8.0_241) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On 2/25/2020 9:59 AM, John Garry wrote: > Hi guys, > > JFYI, When I enable CONFIG_PROVE_RCU=3Dy, I get these: > > [=C2=A0=C2=A0=C2=A0 0.369697] WARNING: suspicious RCU usage > [=C2=A0=C2=A0=C2=A0 0.374179] 5.6.0-rc3-00002-g619882231229-dirty #1753= Not tainted > [=C2=A0=C2=A0=C2=A0 0.380974] ----------------------------- > [=C2=A0=C2=A0=C2=A0 0.385455] security/smack/smack_lsm.c:354 RCU-list t= raversed in non-reader section!! > [=C2=A0=C2=A0=C2=A0 0.394183] > [=C2=A0=C2=A0=C2=A0 0.394183] other info that might help us debug this:= > [=C2=A0=C2=A0=C2=A0 0.394183] > [=C2=A0=C2=A0=C2=A0 0.403107] > [=C2=A0=C2=A0=C2=A0 0.403107] rcu_scheduler_active =3D 1, debug_locks =3D= 1 > [=C2=A0=C2=A0=C2=A0 0.410389] no locks held by kthreadd/2. > [=C2=A0=C2=A0=C2=A0 0.414770] > [=C2=A0=C2=A0=C2=A0 0.414770] stack backtrace: > [=C2=A0=C2=A0=C2=A0 0.419636] CPU: 0 PID: 2 Comm: kthreadd Not tainted = 5.6.0-rc3-00002-g619882231229-dirty #1753 > [=C2=A0=C2=A0=C2=A0 0.429204] Call trace: > [=C2=A0=C2=A0=C2=A0 0.431924]=C2=A0 dump_backtrace+0x0/0x298 > [=C2=A0=C2=A0=C2=A0 0.435990]=C2=A0 show_stack+0x14/0x20 > [=C2=A0=C2=A0=C2=A0 0.439674]=C2=A0 dump_stack+0x118/0x190 > [=C2=A0=C2=A0=C2=A0 0.443548]=C2=A0 lockdep_rcu_suspicious+0xe0/0x120 > [=C2=A0=C2=A0=C2=A0 0.448487]=C2=A0 smack_cred_prepare+0x2f8/0x310 > [=C2=A0=C2=A0=C2=A0 0.453134]=C2=A0 security_prepare_creds+0x64/0xe0 > [=C2=A0=C2=A0=C2=A0 0.457979]=C2=A0 prepare_creds+0x25c/0x368 > [=C2=A0=C2=A0=C2=A0 0.462141]=C2=A0 copy_creds+0x40/0x620 > [=C2=A0=C2=A0=C2=A0 0.465918]=C2=A0 copy_process+0x62c/0x25e0 > [=C2=A0=C2=A0=C2=A0 0.470084]=C2=A0 _do_fork+0xc0/0x998 > [=C2=A0=C2=A0=C2=A0 0.473667]=C2=A0 kernel_thread+0xa0/0xc8 > [=C2=A0=C2=A0=C2=A0 0.477640]=C2=A0 kthreadd+0x2b0/0x408 > [=C2=A0=C2=A0=C2=A0 0.481325]=C2=A0 ret_from_fork+0x10/0x18 > > [=C2=A0=C2=A0 18.804382] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > [=C2=A0=C2=A0 18.808872] WARNING: suspicious RCU usage > [=C2=A0=C2=A0 18.813348] 5.6.0-rc3-00002-g619882231229-dirty #1753 Not = tainted > [=C2=A0=C2=A0 18.820145] ----------------------------- > [=C2=A0=C2=A0 18.824621] security/smack/smack_access.c:87 RCU-list trav= ersed in non-reader section!! > [=C2=A0=C2=A0 18.833544] > [=C2=A0=C2=A0 18.833544] other info that might help us debug this: > [=C2=A0=C2=A0 18.833544] > [=C2=A0=C2=A0 18.842465] > [=C2=A0=C2=A0 18.842465] rcu_scheduler_active =3D 1, debug_locks =3D 1 > [=C2=A0=C2=A0 18.849741] no locks held by kdevtmpfs/781. > [=C2=A0=C2=A0 18.854410] > [=C2=A0=C2=A0 18.854410] stack backtrace: > [=C2=A0=C2=A0 18.859277] CPU: 1 PID: 781 Comm: kdevtmpfs Not tainted 5.= 6.0-rc3-00002-g619882231229-dirty #1753 > [=C2=A0=C2=A0 18.869138] Call trace: > [=C2=A0=C2=A0 18.871860]=C2=A0 dump_backtrace+0x0/0x298 > [=C2=A0=C2=A0 18.875929]=C2=A0 show_stack+0x14/0x20 > [=C2=A0=C2=A0 18.879612]=C2=A0 dump_stack+0x118/0x190 > [=C2=A0=C2=A0 18.883489]=C2=A0 lockdep_rcu_suspicious+0xe0/0x120 > [=C2=A0=C2=A0 18.888428]=C2=A0 smk_access_entry+0x110/0x128 > [=C2=A0=C2=A0 18.892885]=C2=A0 smk_tskacc+0x70/0xe8 > [=C2=A0=C2=A0 18.896568]=C2=A0 smk_curacc+0x64/0x78 > [=C2=A0=C2=A0 18.900249]=C2=A0 smack_inode_permission+0x110/0x1c8 > [=C2=A0=C2=A0 18.905284]=C2=A0 security_inode_permission+0x50/0x98 > [=C2=A0=C2=A0 18.910412]=C2=A0 inode_permission+0x70/0x1d0 > [=C2=A0=C2=A0 18.914768]=C2=A0 link_path_walk.part.38+0x4a8/0x778 > [=C2=A0=C2=A0 18.919802]=C2=A0 path_lookupat+0xd0/0x1a8 > [=C2=A0=C2=A0 18.923871]=C2=A0 filename_lookup+0xf0/0x1f8 > [=C2=A0=C2=A0 18.928136]=C2=A0 user_path_at_empty+0x48/0x58 > [=C2=A0=C2=A0 18.932590]=C2=A0 ksys_chdir+0x8c/0x138 > [=C2=A0=C2=A0 18.936366]=C2=A0 devtmpfsd+0x148/0x448 > [=C2=A0=C2=A0 18.940146]=C2=A0 kthread+0x1c8/0x1d0 > [=C2=A0=C2=A0 18.943732]=C2=A0 ret_from_fork+0x10/0x18 > > I haven't had a chance to check whether they are bogus or not. This is the case where a process with local rules is forked, requiring that a copy of its rules be made for the child. The local rules are not used in any production environment that I know of. It was done for MeeGo. The local rule list really ought to get moved from the cred to the task blob, now that we have one. If this turns out to be real it's unlikely to cause any harm as no one is using local rules. The real fix would take take it out of the cred blob, and that's a significant change. The RCU details should be reviewed at that time. Unless this is worse than it looks. > > Thanks, > John