On Tue 02-04-24 07:38:25, syzbot wrote: > syzbot has found a reproducer for the following issue on: > > HEAD commit: c0b832517f62 Add linux-next specific files for 20240402 > git tree: linux-next > console+strace: https://syzkaller.appspot.com/x/log.txt?x=14af7dd9180000 > kernel config: https://syzkaller.appspot.com/x/.config?x=afcaf46d374cec8c > dashboard link: https://syzkaller.appspot.com/bug?extid=7b219b86935220db6dd8 > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1729f003180000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17fa4341180000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/0d36ec76edc7/disk-c0b83251.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/6f9bb4e37dd0/vmlinux-c0b83251.xz > kernel image: https://storage.googleapis.com/syzbot-assets/2349287b14b7/bzImage-c0b83251.xz > mounted in repro: https://storage.googleapis.com/syzbot-assets/9760c52a227c/mount_0.gz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+7b219b86935220db6dd8@xxxxxxxxxxxxxxxxxxxxxxxxx > > ================================================================== > BUG: KASAN: slab-out-of-bounds in __lock_acquire+0x78/0x1fd0 kernel/locking/lockdep.c:5005 > Read of size 8 at addr ffff888020485fa8 by task kworker/u8:2/35 Looks like the writeback cleanups are causing some use-after-free issues. The code KASAN is complaining about is: /* * Nothing written. Wait for some inode to * become available for writeback. Otherwise * we'll just busyloop. */ trace_writeback_wait(wb, work); inode = wb_inode(wb->b_more_io.prev); >>>>> spin_lock(&inode->i_lock); <<<<<< spin_unlock(&wb->list_lock); /* This function drops i_lock... */ inode_sleep_on_writeback(inode); in wb_writeback(). Now looking at the changes indeed the commit 167d6693deb ("fs/writeback: bail out if there is no more inodes for IO and queued once") is buggy because it will result in trying to fetch 'inode' from empty b_more_io list and thus we'll corrupt memory. I think instead of modifying the condition: if (list_empty(&wb->b_more_io)) { we should do: - if (progress) { + if (progress || !queued) { spin_unlock(&wb->list_lock); continue; } Kemeng? Honza > CPU: 0 PID: 35 Comm: kworker/u8:2 Not tainted 6.9.0-rc2-next-20240402-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024 > Workqueue: writeback wb_workfn (flush-7:1) > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114 > 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 > __lock_acquire+0x78/0x1fd0 kernel/locking/lockdep.c:5005 > lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754 > __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] > _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 > spin_lock include/linux/spinlock.h:351 [inline] > wb_writeback+0x66f/0xd30 fs/fs-writeback.c:2160 > wb_check_old_data_flush fs/fs-writeback.c:2233 [inline] > wb_do_writeback fs/fs-writeback.c:2286 [inline] > wb_workfn+0xba1/0x1090 fs/fs-writeback.c:2314 > process_one_work kernel/workqueue.c:3218 [inline] > process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3299 > worker_thread+0x86d/0xd70 kernel/workqueue.c:3380 > kthread+0x2f0/0x390 kernel/kthread.c:388 > ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243 > </TASK> > > Allocated by task 5052: > kasan_save_stack mm/kasan/common.c:47 [inline] > kasan_save_track+0x3f/0x80 mm/kasan/common.c:68 > poison_kmalloc_redzone mm/kasan/common.c:370 [inline] > __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:387 > kasan_kmalloc include/linux/kasan.h:211 [inline] > __do_kmalloc_node mm/slub.c:4048 [inline] > __kmalloc_noprof+0x200/0x410 mm/slub.c:4061 > kmalloc_noprof include/linux/slab.h:664 [inline] > tomoyo_realpath_from_path+0xcf/0x5e0 security/tomoyo/realpath.c:251 > tomoyo_get_realpath security/tomoyo/file.c:151 [inline] > tomoyo_path_perm+0x2b7/0x740 security/tomoyo/file.c:822 > security_inode_getattr+0xd8/0x130 security/security.c:2269 > vfs_getattr+0x45/0x430 fs/stat.c:173 > vfs_fstat fs/stat.c:198 [inline] > vfs_fstatat+0xd6/0x190 fs/stat.c:300 > __do_sys_newfstatat fs/stat.c:468 [inline] > __se_sys_newfstatat fs/stat.c:462 [inline] > __x64_sys_newfstatat+0x125/0x1b0 fs/stat.c:462 > do_syscall_64+0xfb/0x240 > entry_SYSCALL_64_after_hwframe+0x72/0x7a > > Freed by task 5052: > 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:2180 [inline] > slab_free mm/slub.c:4363 [inline] > kfree+0x149/0x350 mm/slub.c:4484 > tomoyo_realpath_from_path+0x5a9/0x5e0 security/tomoyo/realpath.c:286 > tomoyo_get_realpath security/tomoyo/file.c:151 [inline] > tomoyo_path_perm+0x2b7/0x740 security/tomoyo/file.c:822 > security_inode_getattr+0xd8/0x130 security/security.c:2269 > vfs_getattr+0x45/0x430 fs/stat.c:173 > vfs_fstat fs/stat.c:198 [inline] > vfs_fstatat+0xd6/0x190 fs/stat.c:300 > __do_sys_newfstatat fs/stat.c:468 [inline] > __se_sys_newfstatat fs/stat.c:462 [inline] > __x64_sys_newfstatat+0x125/0x1b0 fs/stat.c:462 > do_syscall_64+0xfb/0x240 > entry_SYSCALL_64_after_hwframe+0x72/0x7a > > The buggy address belongs to the object at ffff888020484000 > which belongs to the cache kmalloc-4k of size 4096 > The buggy address is located 4008 bytes to the right of > allocated 4096-byte region [ffff888020484000, ffff888020485000) > > The buggy address belongs to the physical page: > page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x20480 > head: order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0 > flags: 0xfff80000000040(head|node=0|zone=1|lastcpupid=0xfff) > page_type: 0xffffefff(slab) > raw: 00fff80000000040 ffff888015042140 dead000000000100 dead000000000122 > raw: 0000000000000000 0000000000040004 00000001ffffefff 0000000000000000 > head: 00fff80000000040 ffff888015042140 dead000000000100 dead000000000122 > head: 0000000000000000 0000000000040004 00000001ffffefff 0000000000000000 > head: 00fff80000000003 ffffea0000812001 ffffea0000812048 00000000ffffffff > head: 0000000800000000 0000000000000000 00000000ffffffff 0000000000000000 > page dumped because: kasan: bad access detected > page_owner tracks the page as allocated > page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid -957297381 (swapper/0), ts 1, free_ts 0 > set_page_owner include/linux/page_owner.h:32 [inline] > post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1490 > prep_new_page mm/page_alloc.c:1498 [inline] > get_page_from_freelist+0x2e7e/0x2f40 mm/page_alloc.c:3454 > __alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4712 > __alloc_pages_node_noprof include/linux/gfp.h:244 [inline] > alloc_pages_node_noprof include/linux/gfp.h:271 [inline] > alloc_slab_page+0x5f/0x120 mm/slub.c:2249 > allocate_slab+0x5a/0x2e0 mm/slub.c:2412 > new_slab mm/slub.c:2465 [inline] > ___slab_alloc+0xea8/0x1430 mm/slub.c:3599 > __slab_alloc+0x58/0xa0 mm/slub.c:3684 > __slab_alloc_node mm/slub.c:3737 [inline] > slab_alloc_node mm/slub.c:3915 [inline] > kmalloc_node_trace_noprof+0x20c/0x300 mm/slub.c:4087 > kmalloc_node_noprof include/linux/slab.h:677 [inline] > bdi_alloc+0x4f/0x140 mm/backing-dev.c:894 > __alloc_disk_node+0xb8/0x590 block/genhd.c:1347 > __blk_mq_alloc_disk+0x17d/0x260 block/blk-mq.c:4166 > loop_add+0x448/0xba0 drivers/block/loop.c:2032 > loop_init+0x17a/0x230 drivers/block/loop.c:2275 > do_one_initcall+0x248/0x880 init/main.c:1258 > do_initcall_level+0x157/0x210 init/main.c:1320 > do_initcalls+0x3f/0x80 init/main.c:1336 > page_owner free stack trace missing > > Memory state around the buggy address: > ffff888020485e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > ffff888020485f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > >ffff888020485f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > ^ > ffff888020486000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > ffff888020486080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > ================================================================== > > > --- > If you want syzbot to run the reproducer, reply with: > #syz test: git://repo/address.git branch-or-commit-hash > If you attach or paste a git patch, syzbot will apply it before testing. > -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
