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h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=dVe3CECtBMCtgno1ZnXV4LCwMgXEd+vcNk/CkHl4xjK/0p08Sp2qtYM3IE2mJsCBX Jv0qjX0MwCkFYFLoHLPl57RSQUrdr0McWDph565kfLNLSNuv/YAgoPYhnstyi7nlYP Oc6/kfZCYyu+v0fFEDKccyFZTOWQlTuRFefa31K0= Date: Thu, 10 Oct 2024 14:23:55 -0700 From: Andrew Morton To: syzbot Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, Usama Arif Subject: Re: [syzbot] [mm?] KMSAN: uninit-value in swap_writepage Message-Id: <20241010142355.92225576a955836a67ef746a@linux-foundation.org> In-Reply-To: <670793eb.050a0220.8109b.0003.GAE@google.com> References: <670793eb.050a0220.8109b.0003.GAE@google.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: 5e7g8sxuunjhx5dfi9oie3y9m7sickfc X-Rspamd-Queue-Id: A8D681C0011 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1728595434-262413 X-HE-Meta: U2FsdGVkX1/VuF2HW7yV33/uGjfMqOVdAXoEUrY8l/SFW0UvieTyC7ATU1Ttv2Q8IxuUwTeLMr9vcTTE9+bAgOW09B4NrEDZ7f/t6toMtp82PvlHEf9aErYVxVT31p3RWnUHVT4AZ4K7FEEG/fodZ19uE13ej9pETOTUmLneU703tfX4aktrc6C/R4KO9R1fKRq25Q+wnnfIcXUBxKh/CtH8NWDPiiY2qF3XINQVY5/pQweXk+7j/bE2woiC6yAbkAUhBsK6behPDXERXXwOQ7kQryO3eNXENwjw/wmQemCTY6zC9R9Dx0u8DbBg9epty7UXWCx4ehdzwKELYWA8VXo1ScY0wuwhAU5rKg1FDaPO3CqnlkHvf/kR65jBk2I4GN3wZHGWnbSPqe2ZVcNbBIsyf/dYtXSLjUaz20YSjF9mdUCghV79/jr4pNVxq3rgOxrVBXfBaa8KDna7xPjvD/87Np+lrk5Y/4iDI1+3m6tgQekNNOyevrzQ0XaN58yDtLlJQec1AfwbB2vOxiXIMiF0Y8kHd6MYqd1pcoAFhKuAvGAYmzr8mktGYvgCLO5jFIGoXMfRiWpqDcffNEgrE8rUNzRHbCgWnkPr7J7g2i9mk3e1YeSQsDhMSuU5IP7tvdxf/XtaYxXZ4hv8wqlK0kwpJk/FoY3dUgL+YzUisTeTASyXpe6cDT7GcyOL0uAHJfv0DKOsDV7EMycZ7Kuw6/UwuQnkV6AzH0gzpipi4IMqQVYzTEXEMTHsXJNGZ3HtEi+wd//LnIfi9fDdW1A3gmN7ZI1e+ohr4t74SQ8OArMCDZOSQDaDcI/HrechCwOqAFVYz3fdTOOlIjRRibgBjZR0UzqhjvK3RXaTNivRgR8yAZfOnyK5dQEYJlNbuRb05IoMu+NYs7ifjK7ZOQqXJ1q4d8CTYeqqjrS2aC7Y+g2J1yP4gP2hgBNJkqpFaHPS4LFeKc3fQ9xTfRNHIfm Rt5GPAsK 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 FubCLXl6 CI/3VvQ28ma3TFI4wHlJZfRPSJLzI4Djax0Ys9zZGJweiotceMkkdpbW2QYOOXs+l6ZoxDv0oKV4w/HdACqt83g56Ayh1G4hZEb4ZtJiPhGeRJrjzil+/g== 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 Thu, 10 Oct 2024 01:44:27 -0700 syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: fc20a3e57247 Merge tag 'for-linus-6.12a-rc2-tag' of git://.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=11cdfd27980000 > kernel config: https://syzkaller.appspot.com/x/.config?x=d302f14701986aa0 > dashboard link: https://syzkaller.appspot.com/bug?extid=febb2473441bfb8fb380 > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/5b4b9aca7b75/disk-fc20a3e5.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/b22e17636ec0/vmlinux-fc20a3e5.xz > kernel image: https://storage.googleapis.com/syzbot-assets/5266e625be99/bzImage-fc20a3e5.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+febb2473441bfb8fb380@syzkaller.appspotmail.com Thanks. I'm guessing that shmem symlinks aren't initializing the whole page (folio) and that has tripped up Usama's "store zero pages to be swapped out in a bitmap" feature - it's checking the uninitialized part of the page for zeroness. > ===================================================== > BUG: KMSAN: uninit-value in is_folio_zero_filled mm/page_io.c:189 [inline] > BUG: KMSAN: uninit-value in swap_writepage+0x536/0x12b0 mm/page_io.c:259 > is_folio_zero_filled mm/page_io.c:189 [inline] > swap_writepage+0x536/0x12b0 mm/page_io.c:259 > shmem_writepage+0x2117/0x2450 mm/shmem.c:1567 > pageout mm/vmscan.c:688 [inline] > shrink_folio_list+0x5e78/0x7dd0 mm/vmscan.c:1366 > evict_folios+0x9813/0xbaf0 mm/vmscan.c:4583 > try_to_shrink_lruvec+0x13a3/0x1750 mm/vmscan.c:4778 > shrink_one+0x646/0xd20 mm/vmscan.c:4816 > shrink_many mm/vmscan.c:4879 [inline] > lru_gen_shrink_node mm/vmscan.c:4957 [inline] > shrink_node+0x451a/0x50f0 mm/vmscan.c:5937 > kswapd_shrink_node mm/vmscan.c:6765 [inline] > balance_pgdat mm/vmscan.c:6957 [inline] > kswapd+0x25e2/0x42f0 mm/vmscan.c:7226 > kthread+0x3e2/0x540 kernel/kthread.c:389 > ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 > > Uninit was created at: > __alloc_pages_noprof+0x9d6/0xe70 mm/page_alloc.c:4756 > alloc_pages_mpol_noprof+0x299/0x990 mm/mempolicy.c:2265 > folio_alloc_mpol_noprof+0x55/0x180 mm/mempolicy.c:2283 > shmem_alloc_folio mm/shmem.c:1774 [inline] > shmem_alloc_and_add_folio+0xc33/0x1c30 mm/shmem.c:1813 > shmem_get_folio_gfp+0xacd/0x1f30 mm/shmem.c:2335 > shmem_get_folio mm/shmem.c:2441 [inline] > shmem_symlink+0x528/0xa20 mm/shmem.c:3834 > vfs_symlink+0x1ed/0x460 fs/namei.c:4615 > do_symlinkat+0x257/0x8a0 fs/namei.c:4641 > __do_sys_symlink fs/namei.c:4662 [inline] > __se_sys_symlink fs/namei.c:4660 [inline] > __x64_sys_symlink+0xe0/0x140 fs/namei.c:4660 > x64_sys_call+0x30e8/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:89 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > CPU: 1 UID: 0 PID: 80 Comm: kswapd0 Tainted: G W 6.12.0-rc1-syzkaller-00330-gfc20a3e57247 #0 > Tainted: [W]=WARN > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 > ===================================================== > > > --- > This report is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@googlegroups.com. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > If the report is already addressed, let syzbot know by replying with: > #syz fix: exact-commit-title > > If you want to overwrite report's subsystems, reply with: > #syz set subsystems: new-subsystem > (See the list of subsystem names on the web dashboard) > > If the report is a duplicate of another one, reply with: > #syz dup: exact-subject-of-another-report > > If you want to undo deduplication, reply with: > #syz undup