Details

Issue of the Implementation # F0010

Brief

f2fs: Possible use-after-free when umount filesystem

Detailed Description

While unmount filesystem, f2fs_put_super() deletes 'node_inode' inode, then 'meta_inode' inode via iput(). But f2fs_evict_inode(), called during iput() for 'meta_inode', calls invalidate_mapping_pages() for 'node_inode'.

So, deleting 'meta_inode' uses 'node_inode' object, which could be freed at that moment.

Reproducing

Create f2fs filesystem, mount, then umount it. Use-after-free for 'node_inode' object will be triggered at the last step.

Example

AddressSanitizer: heap-use-after-free in f2fs_evict_inode
Read of size 8 by thread T22279:
 [<ffffffffa02d8702>] f2fs_evict_inode+0x102/0x2e0 [f2fs] /home/tester/linux-sources/linux-kasan/fs/f2fs/f2fs.h:584
 [<ffffffff812359af>] evict+0x15f/0x290 /home/tester/linux-sources/linux-kasan/fs/inode.c:550
 [<     inlined    >] iput+0x196/0x280 iput_final /home/tester/linux-sources/linux-kasan/fs/inode.c:1418
 [<ffffffff812369a6>] iput+0x196/0x280 /home/tester/linux-sources/linux-kasan/fs/inode.c:1436
 [<ffffffffa02dc416>] f2fs_put_super+0xd6/0x170 [f2fs] /home/tester/linux-sources/linux-kasan/fs/f2fs/super.c:434
 [<ffffffff81210095>] generic_shutdown_super+0xc5/0x1b0 /home/tester/linux-sources/linux-kasan/fs/super.c:406
 [<ffffffff812105fd>] kill_block_super+0x4d/0xb0 /home/tester/linux-sources/linux-kasan/fs/super.c:1019
 [<ffffffff81210a86>] deactivate_locked_super+0x66/0x80 /home/tester/linux-sources/linux-kasan/fs/super.c:284
 [<ffffffff81211c98>] deactivate_super+0x68/0x80 /home/tester/linux-sources/linux-kasan/fs/super.c:307
 [<ffffffff8123cc88>] mntput_no_expire+0x198/0x250 /home/tester/linux-sources/linux-kasan/fs/namespace.c:986 (discriminator 3)
 [<     inlined    >] SyS_umount+0xe9/0x1a0 SYSC_umount /home/tester/linux-sources/linux-kasan/fs/namespace.c:1424
 [<ffffffff8123f1c9>] SyS_umount+0xe9/0x1a0 /home/tester/linux-sources/linux-kasan/fs/namespace.c:1392
 [<ffffffff81cc8df9>] system_call_fastpath+0x16/0x1b /home/tester/linux-sources/linux-kasan/arch/x86/kernel/entry_64.S:426

Freed by thread T3:
 [<ffffffffa02dc337>] f2fs_i_callback+0x27/0x30 [f2fs] /home/tester/linux-sources/linux-kasan/fs/f2fs/super.c:408
 [<     inlined    >] rcu_process_callbacks+0x2d6/0x930 __rcu_reclaim /home/tester/linux-sources/linux-kasan/kernel/rcu/rcu.h:114
 [<     inlined    >] rcu_process_callbacks+0x2d6/0x930 rcu_do_batch /home/tester/linux-sources/linux-kasan/kernel/rcu/tree.c:2242
 [<     inlined    >] rcu_process_callbacks+0x2d6/0x930 invoke_rcu_callbacks /home/tester/linux-sources/linux-kasan/kernel/rcu/tree.c:2499
 [<     inlined    >] rcu_process_callbacks+0x2d6/0x930 __rcu_process_callbacks /home/tester/linux-sources/linux-kasan/kernel/rcu/tree.c:2466
 [<ffffffff810fd266>] rcu_process_callbacks+0x2d6/0x930 /home/tester/linux-sources/linux-kasan/kernel/rcu/tree.c:2483
 [<ffffffff8107cce2>] __do_softirq+0x142/0x380 /home/tester/linux-sources/linux-kasan/kernel/softirq.c:269
 [<ffffffff8107cf50>] run_ksoftirqd+0x30/0x50 /home/tester/linux-sources/linux-kasan/kernel/softirq.c:658
 [<ffffffff810b2a87>] smpboot_thread_fn+0x197/0x280 /home/tester/linux-sources/linux-kasan/kernel/smpboot.c:160
 [<ffffffff810a8238>] kthread+0x148/0x160 /home/tester/linux-sources/linux-kasan/kernel/kthread.c:207
 [<ffffffff81cc8d4c>] ret_from_fork+0x7c/0xb0 /home/tester/linux-sources/linux-kasan/arch/x86/kernel/entry_64.S:351

Allocated by thread T22276:
 [<ffffffffa02dc7dd>] f2fs_alloc_inode+0x2d/0x170 [f2fs] /home/tester/linux-sources/linux-kasan/fs/f2fs/super.c:356
 [<ffffffff8123471d>] alloc_inode+0x2d/0xe0 /home/tester/linux-sources/linux-kasan/fs/inode.c:208
 [<ffffffff81235e2a>] iget_locked+0x10a/0x230 /home/tester/linux-sources/linux-kasan/fs/inode.c:1085
 [<ffffffffa02d7495>] f2fs_iget+0x35/0xa80 [f2fs] /home/tester/linux-sources/linux-kasan/fs/f2fs/inode.c:129
 [<ffffffffa02e2393>] f2fs_fill_super+0xb53/0xff0 [f2fs] /home/tester/linux-sources/linux-kasan/fs/f2fs/super.c:1021
 [<ffffffff81211bce>] mount_bdev+0x1de/0x240 /home/tester/linux-sources/linux-kasan/fs/super.c:992
 [<ffffffffa02dbce0>] f2fs_mount+0x10/0x20 [f2fs] /home/tester/linux-sources/linux-kasan/fs/f2fs/super.c:1127
 [<ffffffff81212a85>] mount_fs+0x55/0x220 /home/tester/linux-sources/linux-kasan/fs/super.c:1095
 [<ffffffff8123c026>] vfs_kern_mount+0x66/0x200 /home/tester/linux-sources/linux-kasan/fs/namespace.c:851
 [<     inlined    >] do_mount+0x2b4/0x1120 do_new_mount /home/tester/linux-sources/linux-kasan/fs/namespace.c:2129
 [<ffffffff812400d4>] do_mount+0x2b4/0x1120 /home/tester/linux-sources/linux-kasan/fs/namespace.c:2453
 [<     inlined    >] SyS_mount+0xb2/0x110 SYSC_mount /home/tester/linux-sources/linux-kasan/fs/namespace.c:2647
 [<ffffffff812414a2>] SyS_mount+0xb2/0x110 /home/tester/linux-sources/linux-kasan/fs/namespace.c:2620
 [<ffffffff81cc8df9>] system_call_fastpath+0x16/0x1b /home/tester/linux-sources/linux-kasan/arch/x86/kernel/entry_64.S:426

The buggy address ffff8800587866c8 is located 48 bytes inside
 of 680-byte region [ffff880058786698, ffff880058786940)

Memory state around the buggy address:
 ffff880058786100: ffffffff ffffffff ffffffff ffffffff
 ffff880058786200: ffffffff ffffffff ffffffrr rrrrrrrr
 ffff880058786300: rrrrrrrr rrffffff ffffffff ffffffff
 ffff880058786400: ffffffff ffffffff ffffffff ffffffff
 ffff880058786500: ffffffff ffffffff ffffffff fffffffr
>ffff880058786600: rrrrrrrr rrrrrrrr rrrfffff ffffffff
                                               ^
 ffff880058786700: ffffffff ffffffff ffffffff ffffffff
 ffff880058786800: ffffffff ffffffff ffffffff ffffffff
 ffff880058786900: ffffffff rrrrrrrr rrrrrrrr rrrr....
 ffff880058786a00: ........ ........ ........ ........
 ffff880058786b00: ........ ........ ........ ........
Legend:
 f - 8 freed bytes
 r - 8 redzone bytes
 . - 8 allocated bytes
 x=1..7 - x allocated bytes + (8-x) redzone bytes