From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id BE77BC47071 for ; Thu, 16 Nov 2023 10:04:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5AFDF6B0447; Thu, 16 Nov 2023 05:04:41 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 560DF6B0449; Thu, 16 Nov 2023 05:04:41 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 428696B044A; Thu, 16 Nov 2023 05:04:41 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 33C9E6B0447 for ; Thu, 16 Nov 2023 05:04:41 -0500 (EST) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 0D5311A0C23 for ; Thu, 16 Nov 2023 10:04:41 +0000 (UTC) X-FDA: 81463383162.02.C730685 Received: from 12.mo582.mail-out.ovh.net (12.mo582.mail-out.ovh.net [178.32.125.228]) by imf21.hostedemail.com (Postfix) with ESMTP id 800F11C000D for ; Thu, 16 Nov 2023 10:04:38 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=none; spf=pass (imf21.hostedemail.com: domain of jose.pekkarinen@foxhound.fi designates 178.32.125.228 as permitted sender) smtp.mailfrom=jose.pekkarinen@foxhound.fi; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1700129079; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=tuH8blXo3e/xE/3iWODHbruQmvXHnZ/+I9L+0vDnQ48=; b=d0ebygaXP3ib8PNZJ8UjKytmUID+cow5+tvcDIAFq6thTrjmHqWihKZwf5KlSanTq5fZSR wAc2ZGY7f5xVCXCqHA2M6GCxcv6EUnNdBbYV6Dk14ZM2Hb2LycXDBBJLEVhcLhAP9ybdgc coge2lVDkMhb5pmxcYyA2kOKDPBt23g= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1700129079; a=rsa-sha256; cv=none; b=3c/pID5sjqBdNRgFK7ykzHYIwCRmX6fDzVqI6h7j4tXcD43N+PBoeGjHlspVUcLFN4f7FY lImDojKJPOtmO6ac2MraGPs7ZTKClQARNqm6PVhRycsp5HP7hDrf/T8Q+WvrYmv5+bkpiC qO0UShGu8k9JLiuZ8ViIaymIwIptOMU= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=none; spf=pass (imf21.hostedemail.com: domain of jose.pekkarinen@foxhound.fi designates 178.32.125.228 as permitted sender) smtp.mailfrom=jose.pekkarinen@foxhound.fi; dmarc=none Received: from director7.ghost.mail-out.ovh.net (unknown [10.108.4.105]) by mo582.mail-out.ovh.net (Postfix) with ESMTP id A5DBD29142 for ; Thu, 16 Nov 2023 10:04:36 +0000 (UTC) Received: from ghost-submission-6684bf9d7b-25wj5 (unknown [10.110.171.249]) by director7.ghost.mail-out.ovh.net (Postfix) with ESMTPS id 8A1901FDCE; Thu, 16 Nov 2023 10:04:35 +0000 (UTC) Received: from RCM-web9.webmail.mail.ovh.net ([151.80.29.21]) by ghost-submission-6684bf9d7b-25wj5 with ESMTPSA id R6B7IDPpVWVIRQAAyXHhzg (envelope-from ); Thu, 16 Nov 2023 10:04:35 +0000 MIME-Version: 1.0 Date: Thu, 16 Nov 2023 12:04:35 +0200 From: =?UTF-8?Q?Jos=C3=A9_Pekkarinen?= To: Hugh Dickins Cc: Matthew Wilcox , akpm@linux-foundation.org, skhan@linuxfoundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linux.dev, syzbot+89edd67979b52675ddec@syzkaller.appspotmail.com, Jann Horn Subject: Re: [PATCH] mm/pgtable: return null if no ptl in __pte_offset_map_lock In-Reply-To: <515cb9c1-abcd-c3f3-cc0d-c3cd248b9d6f@google.com> References: <20231115065506.19780-1-jose.pekkarinen@foxhound.fi> <1c4cb1959829ecf4f0c59691d833618c@foxhound.fi> <515cb9c1-abcd-c3f3-cc0d-c3cd248b9d6f@google.com> User-Agent: Roundcube Webmail/1.4.15 Message-ID: <3cd8b7048ee38f5c5e6f9f6c5dab2deb@foxhound.fi> X-Sender: jose.pekkarinen@foxhound.fi Organization: Foxhound Ltd. X-Originating-IP: 192.42.116.185 X-Webmail-UserID: jose.pekkarinen@foxhound.fi Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Ovh-Tracer-Id: 16804056113005307546 X-VR-SPAMSTATE: OK X-VR-SPAMSCORE: -100 X-VR-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgedvkedrudefkedguddtucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecuqfggjfdpvefjgfevmfevgfenuceurghilhhouhhtmecuhedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmnecujfgurhepggffhffvvefujghffgfkgihoihgtgfesthekjhdttderjeenucfhrhhomheplfhoshorucfrvghkkhgrrhhinhgvnhcuoehjohhsvgdrphgvkhhkrghrihhnvghnsehfohighhhouhhnugdrfhhiqeenucggtffrrghtthgvrhhnpedtfeejledvieegvdfgfeeugedtteffjeetgefffeehveduhedtleehffduudfgjeenucffohhmrghinhepghhithhhuhgsrdgtohhmpdhsvghtuhhppghusghunhhtuhdqhhhoshhtpghqvghmuhdqvhhmpgigkeeiqdeigedqkhgvrhhnvghlrdhmugenucfkphepuddvjedrtddrtddruddpudelvddrgedvrdduudeirddukeehpdduhedurdektddrvdelrddvudenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepihhnvghtpeduvdejrddtrddtrddupdhmrghilhhfrhhomhepoehjohhsvgdrphgvkhhkrghrihhnvghnsehfohighhhouhhnugdrfhhiqedpnhgspghrtghpthhtohepuddprhgtphhtthhopehlihhnuhigqdhmmheskhhvrggtkhdrohhrghdpoffvtefjohhsthepmhhoheekvddpmhhouggvpehsmhhtphhouhht X-Stat-Signature: dj9qfaiu434imktqu4ai7d7i8oggk1p7 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 800F11C000D X-Rspam-User: X-HE-Tag: 1700129078-935109 X-HE-Meta: U2FsdGVkX1+d0qZM5vXqcE/zQ6/8At3yItxd/cuwQZmRDHWUutLOJEKiQT4UPN7KocT3yFaAbjzED+REliLubMlRWsIvzKm8RXNRhgQBICo69J5/5pGC/cNzGbTszSfCCpsjtzRRShZAXkzX5sUGzncYKSi9+Pj6nGDAlAijkCCKEk9QIIPzU9A+qx94/dBvkK/zO5RDKSaw8x3639ZNgjs3+l6yyb2oQZgzUbwnKc+fv79yMaynobDzSE2qZ61RKA9zFiBCrq4cPLGiSNIGfS6wMvl2NM7mbL+ZECyMvUtQk9Pi9LAYfF8uCWammkIKk2kD23iUjXxdaac4It2D2gUhHadzFxDZO6mxUX9CphsuXYEUmQe6DHkje94DYUjPOpDuPuC04C/YlZNGGYlLFR1IBp90/zbZaTRZgAML3GYeXg+GEzuzpIkBluo6gSLOrAeGLACAgOl6YjE4KPlZeEe3WqEHp/20YtSvKWzlv9Pa2MTH4yfX/DzSXd0Yo87uYQMlwmEqwstkrjsPL15YhIlaxRxREyxStH2FEaHc44EKEXoiQEYwRGnSmKTRXyWK9IyznJjoQ41Pr7I6M5tsfKLBd6GBfaySzX205pNvX4Z/YTKOBhXegE2K/zorRBQrtZwj39G2BCvYYBkpTglOu8WXzAMFmoQP2dhY3rEuvJcF+Ezs9s4up7PnfX7vWDPkCoj+XI61O6QEM2jN/fyo3qVLDecF0aTMSg2OP+Zv5vwmx3ePyAVVLwUwLtErOhIyUE7H6HRA7tkp+Qx+frQJ9BhuqetgzWN9ZvhP3fjL5f55XPwKYmzJWe37D/OcR9uL2DT0nQ/HisdPi4SwfX7OqQWmFrSVjcvJOoL00s7WYuFp28wBro+iyZhcH3CCjmIgfbw17/YYIkFggHk21w5dismxWWLCCphHuOOWFsQh/crIpY/Xs2D7fopbUNrJ+aX6wj+R/hQcK7II10uuJ00 cesKg32c ZFtNkhKL/+RkO4FXSLwtY54Wi3wqkh4d8I92GZlt6tc/aHHVzrj0ArrvxuB1m0CDcydwZfmZRWAiIe1P83fVAxkqQE50VJeJmu5EKndHHfdL/TRprwPKhMXBv2cInMCoM6a6hrqsklElF70ES9bt+m+SGHsj6olX1XyOEegIlxvVSEHy6VPFCm1vBIpTqXcOLctXV0hk8CDGFixQnMFQFY/Y30u5rKr3SZbwlhE+TlIqzT5g8A1XAXIZDkFiN8qNbSkYx8ZwOVQbQHipik7EFevYqnXhISBYY2L57n6enbndH6uj9+bM6XeS2qgJC7hMjoj2O4yVg+0tjGrQgaLQhSK5U6U5c0txJ0GDeV66ECGNHvnRr6Cn9VC0X5wMXT21MxtbGvWupBrdZfuJKCeR2Elm3MdpD7zKAOxJjN4LS59hffYvkxQASL9Rrow== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2023-11-16 07:23, Hugh Dickins wrote: > On Wed, 15 Nov 2023, Matthew Wilcox wrote: >> On Wed, Nov 15, 2023 at 06:05:30PM +0200, José Pekkarinen wrote: >> >> > > I don't think we should be changing ptlock_ptr(). >> > >> > This is where the null ptr dereference originates, so the only >> > alternative I can think of is to protect the life cycle of the ptdesc >> > to prevent it to die between the pte check and the spin_unlock of >> > __pte_offset_map_lock. Would that work for you? > > Thanks for pursuing this, José, but I agree with Matthew: I don't > think your patch is right at all. The change in ptlock_ptr() did not > make sense to me, and the change in __pte_offset_map_lock() leaves us > still wondering what has gone wrong (and misses an rcu_read_unlock()). > > You mentioned "I tested the syzbot reproducer in x86 and it doesn't > produce this kasan report anymore": are you saying that you were able > to reproduce the issue on x86 (without your patch)? That would be very > interesting (and I think would disprove my hypothesis below). I ought > to try on x86 if you managed to reproduce on it, but it's not worth > the effort if you did not. If you have an x86 stack and registers, > please show (though I'm uncertain how much KASAN spoils the output). Hi, Yes, I have a local setup based in [1], where I can spin a small vm, build the reproducer and run it in. The only thing I took from the webpage is the kernel config file, and the image I made it locally by debootstrapping and running the modifications in create-image.sh manually, the kasan report follows: [ 111.408746][ T8885] general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] PREEMPT SMP KASAN NOPTI [ 111.413181][ T8885] KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f] [ 111.413181][ T8885] CPU: 1 PID: 8885 Comm: handle_kernel_p Not tainted 6.7.0-rc1-00007-ge612cb00e200 #6 [ 111.413181][ T8885] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 [ 111.413181][ T8885] RIP: 0010:__pte_offset_map_lock+0xfa/0x310 [ 111.423642][ T8885] Code: 48 c1 e8 03 80 3c 10 00 0f 85 12 02 00 00 4c 03 3d db 92 cf 0b 48 b8 00 00 00 00 00 fc ff df 49 8d 7f 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 e2 01 00 00 4d 8b 7f 28 4c 89 ff e8 f0 a1 3a 09 [ 111.423642][ T8885] RSP: 0018:ffffc90005baf738 EFLAGS: 00010216 [ 111.423642][ T8885] RAX: dffffc0000000000 RBX: 0005800000000067 RCX: ffffffff81ada02e [ 111.423642][ T8885] RDX: 0000000000000005 RSI: ffffffff81ad9f0f RDI: 0000000000000028 [ 111.423642][ T8885] RBP: ffff8880224c4800 R08: 0000000000000007 R09: 0000000000000000 [ 111.423642][ T8885] R10: 0000000000000000 R11: 0000000000000000 R12: 0005088000000a80 [ 111.423642][ T8885] R13: 1ffff92000b75ee9 R14: ffffc90005bafa88 R15: 0000000000000000 [ 111.423642][ T8885] FS: 00007f8d3972c6c0(0000) GS:ffff888069700000(0000) knlGS:0000000000000000 [ 111.423642][ T8885] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 111.423642][ T8885] CR2: 00007f8d3970af78 CR3: 00000000224d6000 CR4: 00000000000006f0 [ 111.423642][ T8885] Call Trace: [ 111.423642][ T8885] [ 111.423642][ T8885] ? show_regs+0x8f/0xa0 [ 111.423642][ T8885] ? die_addr+0x4f/0xd0 [ 111.423642][ T8885] ? exc_general_protection+0x150/0x220 [ 111.423642][ T8885] ? asm_exc_general_protection+0x26/0x30 [ 111.423642][ T8885] ? __pte_offset_map_lock+0x1de/0x310 [ 111.423642][ T8885] ? __pte_offset_map_lock+0xbf/0x310 [ 111.423642][ T8885] ? __pte_offset_map_lock+0xfa/0x310 [ 111.423642][ T8885] ? __pte_offset_map_lock+0xbf/0x310 [ 111.423642][ T8885] ? __pfx___pte_offset_map_lock+0x10/0x10 [ 111.423642][ T8885] filemap_map_pages+0x336/0x13b0 [ 111.423642][ T8885] ? __pfx_filemap_map_pages+0x10/0x10 [ 111.423642][ T8885] ? rcu_read_unlock+0x33/0xb0 [ 111.423642][ T8885] do_fault+0x86a/0x1350 [ 111.423642][ T8885] __handle_mm_fault+0xe53/0x23a0 [ 111.423642][ T8885] ? __pfx___handle_mm_fault+0x10/0x10 [ 111.483413][ T8885] handle_mm_fault+0x369/0x890 [ 111.483413][ T8885] __get_user_pages+0x46d/0x15d0 [ 111.483413][ T8885] ? __pfx___get_user_pages+0x10/0x10 [ 111.483413][ T8885] populate_vma_page_range+0x2de/0x420 [ 111.483413][ T8885] ? __pfx_populate_vma_page_range+0x10/0x10 [ 111.483413][ T8885] ? __pfx_find_vma_intersection+0x10/0x10 [ 111.483413][ T8885] ? vm_mmap_pgoff+0x299/0x3c0 [ 111.483413][ T8885] __mm_populate+0x1da/0x380 [ 111.483413][ T8885] ? __pfx___mm_populate+0x10/0x10 [ 111.483413][ T8885] ? up_write+0x1b3/0x520 [ 111.483413][ T8885] vm_mmap_pgoff+0x2d1/0x3c0 [ 111.483413][ T8885] ? __pfx_vm_mmap_pgoff+0x10/0x10 [ 111.483413][ T8885] ksys_mmap_pgoff+0x7d/0x5b0 [ 111.483413][ T8885] __x64_sys_mmap+0x125/0x190 [ 111.483413][ T8885] do_syscall_64+0x45/0xf0 [ 111.483413][ T8885] entry_SYSCALL_64_after_hwframe+0x6e/0x76 [ 111.483413][ T8885] RIP: 0033:0x7f8d39831559 [ 111.483413][ T8885] Code: 08 89 e8 5b 5d c3 66 2e 0f 1f 84 00 00 00 00 00 90 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 8b 0d 77 08 0d 00 f7 d8 64 89 01 48 [ 111.483413][ T8885] RSP: 002b:00007f8d3972be78 EFLAGS: 00000216 ORIG_RAX: 0000000000000009 [ 111.483413][ T8885] RAX: ffffffffffffffda RBX: 00007f8d3972c6c0 RCX: 00007f8d39831559 [ 111.483413][ T8885] RDX: b635773f07ebbeea RSI: 0000000000b36000 RDI: 0000000020000000 [ 111.483413][ T8885] RBP: 00007f8d3972bea0 R08: 00000000ffffffff R09: 0000000000000000 [ 111.483413][ T8885] R10: 0000000000008031 R11: 0000000000000216 R12: ffffffffffffff80 [ 111.483413][ T8885] R13: 0000000000000000 R14: 00007fffcef921d0 R15: 00007f8d3970c000 [ 111.483413][ T8885] [ 111.483413][ T8885] Modules linked in: [ 111.763549][ T8885] ---[ end trace 0000000000000000 ]--- [ 111.773557][ T8885] RIP: 0010:__pte_offset_map_lock+0xfa/0x310 [ 111.776045][ T8885] Code: 48 c1 e8 03 80 3c 10 00 0f 85 12 02 00 00 4c 03 3d db 92 cf 0b 48 b8 00 00 00 00 00 fc ff df 49 8d 7f 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 e2 01 00 00 4d 8b 7f 28 4c 89 ff e8 f0 a1 3a 09 [ 111.805040][ T8885] RSP: 0018:ffffc90005baf738 EFLAGS: 00010216 [ 111.820041][ T8885] RAX: dffffc0000000000 RBX: 0005800000000067 RCX: ffffffff81ada02e [ 111.837884][ T8885] RDX: 0000000000000005 RSI: ffffffff81ad9f0f RDI: 0000000000000028 [ 111.855313][ T8885] RBP: ffff8880224c4800 R08: 0000000000000007 R09: 0000000000000000 [ 111.878314][ T8885] R10: 0000000000000000 R11: 0000000000000000 R12: 0005088000000a80 [ 111.910624][ T8885] R13: 1ffff92000b75ee9 R14: ffffc90005bafa88 R15: 0000000000000000 [ 111.923627][ T8885] FS: 00007f8d3972c6c0(0000) GS:ffff888069700000(0000) knlGS:0000000000000000 [ 111.932017][ T8885] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 111.941166][ T8885] CR2: 00007fa26ac38178 CR3: 00000000224d6000 CR4: 00000000000006f0 [ 111.950619][ T8885] Kernel panic - not syncing: Fatal exception [ 111.953981][ T8885] Kernel Offset: disabled [ 111.953981][ T8885] Rebooting in 86400 seconds.. I can test some patches for you if it helps finding out the issue. [1] https://github.com/google/syzkaller/blob/master/docs/linux/setup_ubuntu-host_qemu-vm_x86-64-kernel.md José.