From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 DE2491DC05C; Fri, 13 Sep 2024 13:55:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726235727; cv=none; b=k5RvvB3WZvb5fhrCX+lWpf2OEhQX9HeA7KmbCRk9H3R7veLxW7VLduRNQ/+O4Y3fdWoOl2oQe5m4XH7Ei5EMF++uzLfRtIyLmfDEWSqOIhpRFVXVwcy1Iwbrg5XlLuUCYXjg2MZ5fhghVarSSdC/pSs5cvYBnSWcaQzyIMawHYQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726235727; c=relaxed/simple; bh=oXazqEKDh0tAXw5ldH6EeU5zLIRYchYyy7PuXPu4XyY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=f24prMrNSFFqd7xCH0IDmAjsvHu6Ykw0Cp1qUSz1brcFBAPBchQeq1VE0ddATvOJjF95YkhOg8I18/f3ZhMZ8sS5bFFXG/9+y82GjtApjQmgcIvo5SQjuhklcWBbcgE5e+4BlD2JOvrz8yy6fMxTpy6gY4WcrFTk+QxgQLUGfA4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=swOMMPxy; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="swOMMPxy" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=ukaDfgZI5gyswKyGd9RyUNeHhjbD+lqgoaj3eehBdls=; b=swOMMPxyEy7Ioqk+jDcYTNAHYf 6/8YGbokqCJKbUOOClv9kvgCSx6wVMAjbOnNVDDi4fmecmsxBHPmyZtSlL2AUHtd3vh+u8V1tXeZS ZWpQGh/iKnq3/SN1OSxNS9WIrCabvdldVKZ9CSsre6f7vmNqXdZc5cg+U0iWwWH2GN+cdl67pTwyp L16rS/V4sPvG/6z+8vCR3N3wv8fSYphs4VSWUmSQrVR1KLuR5aqD6IQX0+bjqBZ+ZDk2muycn9L6M wf51zhWEr6+5LlBDURQ4ieI5WlFZSP/bcodJXbPDiUdWRAXGYBCjsd6QBqxdhWrZruaKoJOiSA0Zl NXoyNyKw==; Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1sp6lb-0000000GdYm-00Qk; Fri, 13 Sep 2024 13:55:19 +0000 Date: Fri, 13 Sep 2024 14:55:18 +0100 From: Matthew Wilcox To: Hillf Danton Cc: syzbot , Jan Kara , Tetsuo Handa , Linus Torvalds , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [fs?] KASAN: slab-use-after-free Read in invalidate_bh_lru Message-ID: References: <0000000000005c2d960621e89afe@google.com> <20240913123104.367-1-hdanton@sina.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240913123104.367-1-hdanton@sina.com> On Fri, Sep 13, 2024 at 08:31:04PM +0800, Hillf Danton wrote: > On Thu, 12 Sep 2024 02:19:26 -0700 > > ================================================================== > > BUG: KASAN: slab-use-after-free in instrument_atomic_read include/linux/instrumented.h:68 [inline] > > BUG: KASAN: slab-use-after-free in atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline] > > BUG: KASAN: slab-use-after-free in __brelse fs/buffer.c:1235 [inline] > > BUG: KASAN: slab-use-after-free in brelse include/linux/buffer_head.h:325 [inline] > > BUG: KASAN: slab-use-after-free in __invalidate_bh_lrus fs/buffer.c:1508 [inline] > > BUG: KASAN: slab-use-after-free in invalidate_bh_lru+0xa8/0x1b0 fs/buffer.c:1521 > > Read of size 4 at addr ffff88801c989a58 by task udevd/5114 > > > A worse case than the report looks like > > buff head is freed and reused with bh lru left intact How is that supposed to happen? We take a reference to the BH when it goes on the LRU list, so it shouldn't be freed. We free BHs in free_buffer_head(). That's called from two places; the failure path of folio_alloc_buffers() and try_to_free_buffers(). try_to_free_buffers() calls drop_buffers() first, which checks buffer_busy(), which will fail if bh->b_count is non-zero. You can't even get to the BHs in folio_alloc_buffers() because they're not attached to anything until the function returns. So I have no idea what the problem is here. And also I don't think it's my responsibility to track it down. I'm not the buffer_head maintainer. > flush bh lru > __brelse() > if (atomic_read(&bh->b_count)) { > put_bh(bh); > return; > } > > and bh->b_count gets corrupted by put_bh(). > > > CPU: 0 UID: 0 PID: 5114 Comm: udevd Not tainted 6.11.0-rc6-syzkaller-00308-gb31c44928842 #0 > > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 > > Call Trace: > > > > __dump_stack lib/dump_stack.c:93 [inline] > > dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119 > > print_address_description mm/kasan/report.c:377 [inline] > > print_report+0x169/0x550 mm/kasan/report.c:488 > > kasan_report+0x143/0x180 mm/kasan/report.c:601 > > kasan_check_range+0x282/0x290 mm/kasan/generic.c:189 > > instrument_atomic_read include/linux/instrumented.h:68 [inline] > > atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline] > > __brelse fs/buffer.c:1235 [inline] > > brelse include/linux/buffer_head.h:325 [inline] > > __invalidate_bh_lrus fs/buffer.c:1508 [inline] > > invalidate_bh_lru+0xa8/0x1b0 fs/buffer.c:1521 > > csd_do_func kernel/smp.c:134 [inline] > > smp_call_function_many_cond+0x15d7/0x29d0 kernel/smp.c:847 > > on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1023 > > kill_bdev block/bdev.c:89 [inline] > > blkdev_flush_mapping+0xfe/0x250 block/bdev.c:664 > > blkdev_put_whole block/bdev.c:671 [inline] > > bdev_release+0x466/0x700 block/bdev.c:1096 > > blkdev_release+0x15/0x20 block/fops.c:638 > > __fput+0x24a/0x8a0 fs/file_table.c:422 > > __do_sys_close fs/open.c:1566 [inline] > > __se_sys_close fs/open.c:1551 [inline] > > __x64_sys_close+0x7f/0x110 fs/open.c:1551 > > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > > do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 > > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > RIP: 0033:0x7f8226f170a8 > > Code: 48 8b 05 83 9d 0d 00 64 c7 00 16 00 00 00 83 c8 ff 48 83 c4 20 5b c3 64 8b 04 25 18 00 00 00 85 c0 75 20 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 76 5b 48 8b 15 51 9d 0d 00 f7 d8 64 89 02 48 83 > > RSP: 002b:00007ffe0319be58 EFLAGS: 00000246 ORIG_RAX: 0000000000000003 > > RAX: ffffffffffffffda RBX: 00007f8226dee0e0 RCX: 00007f8226f170a8 > > RDX: 000056579a6766d5 RSI: 00007ffe0319b658 RDI: 0000000000000008 > > RBP: 00005652ff487f60 R08: 0000000000000006 R09: b595b5b875e4bbae > > R10: 000000000000010f R11: 0000000000000246 R12: 0000000000000002 > > R13: 00005652ff478840 R14: 0000000000000008 R15: 00005652ff466910 > > > > > > Allocated by task 5112: > > kasan_save_stack mm/kasan/common.c:47 [inline] > > kasan_save_track+0x3f/0x80 mm/kasan/common.c:68 > > unpoison_slab_object mm/kasan/common.c:312 [inline] > > __kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:338 > > kasan_slab_alloc include/linux/kasan.h:201 [inline] > > slab_post_alloc_hook mm/slub.c:3992 [inline] > > slab_alloc_node mm/slub.c:4041 [inline] > > kmem_cache_alloc_noprof+0x135/0x2a0 mm/slub.c:4048 > > alloc_buffer_head+0x2a/0x290 fs/buffer.c:3025 > > folio_alloc_buffers+0x241/0x5b0 fs/buffer.c:929 > > grow_dev_folio fs/buffer.c:1072 [inline] > > grow_buffers fs/buffer.c:1113 [inline] > > __getblk_slow fs/buffer.c:1139 [inline] > > bdev_getblk+0x2a6/0x550 fs/buffer.c:1441 > > __bread_gfp+0x86/0x400 fs/buffer.c:1495 > > sb_bread include/linux/buffer_head.h:347 [inline] > > sysv_fill_super+0x231/0x710 fs/sysv/super.c:379 > > mount_bdev+0x20a/0x2d0 fs/super.c:1679 > > legacy_get_tree+0xee/0x190 fs/fs_context.c:662 > > vfs_get_tree+0x90/0x2b0 fs/super.c:1800 > > do_new_mount+0x2be/0xb40 fs/namespace.c:3472 > > do_mount fs/namespace.c:3812 [inline] > > __do_sys_mount fs/namespace.c:4020 [inline] > > __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:3997 > > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > > do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 > > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > > > Freed by task 79: > > kasan_save_stack mm/kasan/common.c:47 [inline] > > kasan_save_track+0x3f/0x80 mm/kasan/common.c:68 > > kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579 > > poison_slab_object+0xe0/0x150 mm/kasan/common.c:240 > > __kasan_slab_free+0x37/0x60 mm/kasan/common.c:256 > > kasan_slab_free include/linux/kasan.h:184 [inline] > > slab_free_hook mm/slub.c:2256 [inline] > > slab_free mm/slub.c:4477 [inline] > > kmem_cache_free+0x145/0x350 mm/slub.c:4552 > > free_buffer_head+0x54/0x240 fs/buffer.c:3041 > > try_to_free_buffers+0x311/0x5f0 fs/buffer.c:2982 > > shrink_folio_list+0x26c2/0x8c90 mm/vmscan.c:1413 > > evict_folios+0x50f7/0x7780 mm/vmscan.c:4560 > > try_to_shrink_lruvec+0x9ab/0xbb0 mm/vmscan.c:4755 > > shrink_one+0x3b9/0x850 mm/vmscan.c:4793 > > shrink_many mm/vmscan.c:4856 [inline] > > lru_gen_shrink_node mm/vmscan.c:4934 [inline] > > shrink_node+0x3799/0x3de0 mm/vmscan.c:5914 > > kswapd_shrink_node mm/vmscan.c:6742 [inline] > > balance_pgdat mm/vmscan.c:6934 [inline] > > kswapd+0x1cbc/0x3720 mm/vmscan.c:7203 > > kthread+0x2f0/0x390 kernel/kthread.c:389 > > ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147 > > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 > > > > The buggy address belongs to the object at ffff88801c9899f8 > > which belongs to the cache buffer_head of size 168 > > The buggy address is located 96 bytes inside of > > freed 168-byte region [ffff88801c9899f8, ffff88801c989aa0) > > > > The buggy address belongs to the physical page: > > page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1c989 > > flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff) > > page_type: 0xfdffffff(slab) > > raw: 00fff00000000000 ffff88801b763c80 ffffea0000725d40 0000000000000006 > > raw: 0000000000000000 0000000080110011 00000001fdffffff 0000000000000000 > > page dumped because: kasan: bad access detected > > page_owner tracks the page as allocated > > page last allocated via order 0, migratetype Reclaimable, gfp_mask 0x152c50(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_HARDWALL|__GFP_RECLAIMABLE), pid 1, tgid 1 (init), ts 28576033639, free_ts 0 > > set_page_owner include/linux/page_owner.h:32 [inline] > > post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1500 > > prep_new_page mm/page_alloc.c:1508 [inline] > > get_page_from_freelist+0x2e4c/0x2f10 mm/page_alloc.c:3446 > > __alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4702 > > __alloc_pages_node_noprof include/linux/gfp.h:269 [inline] > > alloc_pages_node_noprof include/linux/gfp.h:296 [inline] > > alloc_slab_page+0x5f/0x120 mm/slub.c:2325 > > allocate_slab+0x5a/0x2f0 mm/slub.c:2488 > > new_slab mm/slub.c:2541 [inline] > > ___slab_alloc+0xcd1/0x14b0 mm/slub.c:3727 > > __slab_alloc+0x58/0xa0 mm/slub.c:3817 > > __slab_alloc_node mm/slub.c:3870 [inline] > > slab_alloc_node mm/slub.c:4029 [inline] > > kmem_cache_alloc_noprof+0x1c1/0x2a0 mm/slub.c:4048 > > alloc_buffer_head+0x2a/0x290 fs/buffer.c:3025 > > folio_alloc_buffers+0x241/0x5b0 fs/buffer.c:929 > > grow_dev_folio fs/buffer.c:1072 [inline] > > grow_buffers fs/buffer.c:1113 [inline] > > __getblk_slow fs/buffer.c:1139 [inline] > > bdev_getblk+0x2a6/0x550 fs/buffer.c:1441 > > __getblk include/linux/buffer_head.h:381 [inline] > > sb_getblk include/linux/buffer_head.h:387 [inline] > > ext4_read_inode_bitmap+0x24c/0x12f0 fs/ext4/ialloc.c:145 > > __ext4_new_inode+0x106f/0x4260 fs/ext4/ialloc.c:1054 > > ext4_create+0x279/0x550 fs/ext4/namei.c:2832 > > lookup_open fs/namei.c:3578 [inline] > > open_last_lookups fs/namei.c:3647 [inline] > > path_openat+0x1a9a/0x3470 fs/namei.c:3883 > > do_filp_open+0x235/0x490 fs/namei.c:3913 > > page_owner free stack trace missing > > > > Memory state around the buggy address: > > ffff88801c989900: fc fc fa fb fb fb fb fb fb fb fb fb fb fb fb fb > > ffff88801c989980: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fa > > >ffff88801c989a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ^ > > ffff88801c989a80: fb fb fb fb fc fc fc fc fc fc fc fc 00 00 00 00 > > ffff88801c989b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > > ==================================================================