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 2A06544E05C for ; Fri, 31 Jul 2026 16:07:28 +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=1785514052; cv=none; b=WfyYPhtcVxJfbVFFtSXlLxc4lZBl2X8z9QLB8zr1Dn/Y1eF9Bg8PbKyXd3P6APUPld8Mq5XhtbVSF+3E5uqfnBMoJAlVxOPELCMYguW7V/k63KjxQv3+d+3OwFRBV9czqYhDJnMfn4szyWiGD7lpeSEgf+4S/zgr0D7+qE8jGjQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785514052; c=relaxed/simple; bh=3O1cz5zbT73jIWVuWfvb8/Y7yS6fr3m2dRPrfhPw+zA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=WVfbY9s3eTolngTzxxc9l+BcXfy4p7zr1fJ89yr8nVQYYHAzCFXh3SRU7BtP3DD1B8nUS8oqi/LzTwmcwNSxNNSQk9brTYjw1A7Lx/dkXdLTGvKMBWP2YepCBu5ZfN1Q2jU2DwEuiOzhmc0R4bMYX9DajPFEuHHlp7SdhFYtisY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QOCI1flx; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="QOCI1flx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 20A9A1F00AC4; Fri, 31 Jul 2026 16:07:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785514048; bh=WYefLO9Ts6Muw+5ON5ixE0yWQxfz5EGL7n7UPE84iiM=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=QOCI1flx/yhiDcNB+AZ7CVXNt+dea6b/SPzicEWBd3ke459a4P0p+nvZgcTfyR7l4 Z7eDSlCJW+T9suLuNzCiW2U4dfQSoL83XFE8ty9xGsBFfPf3mb0hPHPx2zMRgWKU1R mxzeeN1wNUJJ/wHlABxIJDLx/z3HFbOC+atwfY0iPU6gHwSgwQpGPLEyI7mfM3q5i+ jET5L6ISuvEOMx56dRysjbtIcvdlHQk+a1ADsGq4+pvmn7HOfS8GIzDorSAvFBesEE f5btpZ0HtRYtzlzvs7xJSOS6RzlM8Wc+UBWsHeNajvjkOEY0zG8kbp9K6ELIhzsw5T bq6t7wVWVd28A== Message-ID: Date: Fri, 31 Jul 2026 18:07:24 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [syzbot] [mm?] WARNING in mas_nomem Content-Language: en-US To: "Liam R. Howlett" , syzbot Cc: akpm@linux-foundation.org, jannh@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ljs@kernel.org, pfalcato@suse.de, syzkaller-bugs@googlegroups.com, Jason Gunthorpe References: <6a6c4f18.b1a781d0.210f9.001f.GAE@google.com> <6yf7k4fmg4tkbmli6t4qzrk2eiyuuynoc2oimbgaebught2yh5@dspb7xile3kj> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: <6yf7k4fmg4tkbmli6t4qzrk2eiyuuynoc2oimbgaebught2yh5@dspb7xile3kj> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/31/26 17:59, Liam R. Howlett wrote: > On 26/07/31 12:30AM, syzbot wrote: >> Hello, >> >> syzbot found the following issue on: >> >> HEAD commit: cc2b5f627e8c Add linux-next specific files for 20260714 >> git tree: linux-next >> console output: https://syzkaller.appspot.com/x/log.txt?x=15ce5632580000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=2290ccbf984c524f >> dashboard link: https://syzkaller.appspot.com/bug?extid=78a7af91b68fc6394771 >> compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=179151b9580000 >> >> Downloadable assets: >> disk image: https://storage.googleapis.com/syzbot-assets/6836f8efb1da/disk-cc2b5f62.raw.xz >> vmlinux: https://storage.googleapis.com/syzbot-assets/0109d3477cc7/vmlinux-cc2b5f62.xz >> kernel image: https://storage.googleapis.com/syzbot-assets/c2e49e350bbf/bzImage-cc2b5f62.xz >> >> IMPORTANT: if you fix the issue, please add the following tag to the commit: >> Reported-by: syzbot+78a7af91b68fc6394771@syzkaller.appspotmail.com >> >> ------------[ cut here ]------------ >> !mas->sheaf && !mas->alloc >> WARNING: lib/maple_tree.c:5751 at mas_nomem+0x1cc/0x210 lib/maple_tree.c:5751, CPU#0: udevd/5627 >> Modules linked in: >> CPU: 0 UID: 0 PID: 5627 Comm: udevd Not tainted syzkaller #0 PREEMPT_{RT,(full)} >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026 >> RIP: 0010:mas_nomem+0x1cc/0x210 lib/maple_tree.c:5751 >> Code: 4c 89 ff e8 d6 85 ea f6 49 c7 07 00 00 00 00 b0 01 e9 95 fe ff ff e8 f3 2d 7e f6 90 0f 0b 90 e9 2b ff ff ff e8 e5 2d 7e f6 90 <0f> 0b 90 e9 77 fe ff ff 89 d1 80 e1 07 80 c1 03 38 c1 0f 8c ce fe >> RSP: 0018:ffffc9000562f8f0 EFLAGS: 00010293 >> RAX: ffffffff8b4775cb RBX: 1ffff92000ac5fbf RCX: ffff8880366e3e80 >> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 >> RBP: 0000000000000cc0 R08: 00000000ffffffff R09: 1ffffffff1ca1a86 >> R10: dffffc0000000000 R11: fffffbfff1ca1a87 R12: dffffc0000000000 >> R13: ffffc9000562fe18 R14: ffffc9000562fde0 R15: ffffc9000562fdf8 >> FS: 00007f9021203880(0000) GS:ffff8881259f2000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: 000056467bb0d750 CR3: 0000000046416000 CR4: 00000000003526f0 >> Call Trace: >> >> mas_store_gfp+0x37a/0x820 lib/maple_tree.c:4987 >> vma_iter_clear_gfp include/linux/mm.h:1674 [inline] >> do_vmi_align_munmap+0x30c/0x4d0 mm/vma.c:1644 >> do_vmi_munmap+0x252/0x2d0 mm/vma.c:1697 >> __vm_munmap+0x241/0x3e0 mm/vma.c:3347 >> __do_sys_munmap mm/mmap.c:1079 [inline] >> __se_sys_munmap mm/mmap.c:1076 [inline] >> __x64_sys_munmap+0x60/0x70 mm/mmap.c:1076 >> do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] >> do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85 >> entry_SYSCALL_64_after_hwframe+0x77/0x7f >> RIP: 0033:0x7f9021368097 >> Code: 73 01 c3 48 8b 0d 61 2d 0d 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 0b 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 31 2d 0d 00 f7 d8 64 89 01 48 >> RSP: 002b:00007ffeaf32d0a8 EFLAGS: 00000206 ORIG_RAX: 000000000000000b >> RAX: ffffffffffffffda RBX: 000056467bad9bf0 RCX: 00007f9021368097 >> RDX: 0000000000000000 RSI: 00000000009480e8 RDI: 00007f90208ba000 >> RBP: 000056467bad9910 R08: 000056467baec140 R09: 0000000000000006 >> R10: 0000000000000000 R11: 0000000000000206 R12: 00005646569e2588 >> R13: 00007ffeaf32d130 R14: 0000000000000000 R15: 0000000000000000 >> > > > Okay, so I'm going to change this warn_on again. > > The plan is to: > 1. Make mas_erase() and mtree_erase() use __NO_FAIL on retry. __GFP_NOFAIL to be precise. > 2. Remove the warning so that any failures won't cause the warning. > 3. Make mas_store() use __NO_FAIL on retry, like mas_erase(). > 4. Add the check for locks that cannot sleep to mas_store(). > > Basically any caller that cannot correctly return the failure will avoid > failing by allocating with __NO_FAIL. This means the warning is not > necessary. Sounds good. > Thanks to Vlastimil and Pedro for the help on the plan. > > Summary of previous conversation is here: > https://lore.kernel.org/all/20260618152451.GE231643@ziepe.ca/ Yeah, unfortunately, "too small to fail" is a lie, because in some cases it can fail (such as the task itself becoming oom killer victim) or any of the other conditions that can cause __alloc_pages_may_oom() return with *did_some_progress == 0. And syzbot knows how to remind us of this, using fault injection. > > Cheers, > Liam