[syzbot] [nilfs?] KASAN: slab-use-after-free Read in nilfs_load_inode_block

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fc4354c6e5c2 Merge tag 'mm-stable-2023-05-06-10-49' of git..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=16be474a280000
kernel config: https://syzkaller.appspot.com/x/.config?x=73a06f6ef2d5b492
dashboard link: https://syzkaller.appspot.com/bug?extid=78d4495558999f55d1da
compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16cd28ea280000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1273a95c280000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5f4adc5d40b0/disk-fc4354c6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0e06af6b6985/vmlinux-fc4354c6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7d99bbab1361/bzImage-fc4354c6.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/dd743241f9e7/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+78d449...@syzkaller.appspotmail.com

NILFS (loop2): error -5 truncating bmap (ino=15)
==================================================================
BUG: KASAN: slab-use-after-free in nilfs_load_inode_block+0x11e/0x280 fs/nilfs2/inode.c:1012
Read of size 8 at addr ffff88801f47f430 by task syz-executor323/4999

CPU: 0 PID: 4999 Comm: syz-executor323 Not tainted 6.3.0-syzkaller-13466-gfc4354c6e5c2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:351 [inline]
print_report+0x163/0x540 mm/kasan/report.c:462
kasan_report+0x176/0x1b0 mm/kasan/report.c:572
nilfs_load_inode_block+0x11e/0x280 fs/nilfs2/inode.c:1012
__nilfs_mark_inode_dirty+0xa5/0x280 fs/nilfs2/inode.c:1089
nilfs_mark_inode_dirty fs/nilfs2/nilfs.h:288 [inline]
nilfs_evict_inode+0x189/0x420 fs/nilfs2/inode.c:934
evict+0x2a4/0x620 fs/inode.c:665
nilfs_dispose_list+0x51d/0x5c0 fs/nilfs2/segment.c:816
nilfs_detach_log_writer+0xaf1/0xbb0 fs/nilfs2/segment.c:2852
nilfs_put_super+0x4d/0x160 fs/nilfs2/super.c:477
generic_shutdown_super+0x134/0x340 fs/super.c:500
kill_block_super+0x84/0xf0 fs/super.c:1407
deactivate_locked_super+0xa4/0x110 fs/super.c:331
cleanup_mnt+0x426/0x4c0 fs/namespace.c:1177
task_work_run+0x24a/0x300 kernel/task_work.c:179
ptrace_notify+0x2cd/0x380 kernel/signal.c:2369
ptrace_report_syscall include/linux/ptrace.h:411 [inline]
ptrace_report_syscall_exit include/linux/ptrace.h:473 [inline]
syscall_exit_work kernel/entry/common.c:252 [inline]
syscall_exit_to_user_mode_prepare kernel/entry/common.c:279 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:284 [inline]
syscall_exit_to_user_mode+0x157/0x280 kernel/entry/common.c:297
do_syscall_64+0x4d/0xc0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f0b39ccba87
Code: ff d0 48 89 c7 b8 3c 00 00 00 0f 05 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 b8 a6 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffcfc3da598 EFLAGS: 00000202 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f0b39ccba87
RDX: 00007ffcfc3da659 RSI: 000000000000000a RDI: 00007ffcfc3da650
RBP: 00007ffcfc3da650 R08: 00000000ffffffff R09: 00007ffcfc3da430
R10: 00005555563da683 R11: 0000000000000202 R12: 00007ffcfc3db710
R13: 00005555563da5f0 R14: 00007ffcfc3da5c0 R15: 00007ffcfc3db730
</TASK>

Allocated by task 5216:
kasan_save_stack mm/kasan/common.c:45 [inline]
kasan_set_track+0x4f/0x70 mm/kasan/common.c:52
____kasan_kmalloc mm/kasan/common.c:374 [inline]
__kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:383
kmalloc include/linux/slab.h:559 [inline]
kzalloc include/linux/slab.h:680 [inline]
nilfs_find_or_create_root+0x137/0x4e0 fs/nilfs2/the_nilfs.c:810
nilfs_attach_checkpoint+0x123/0x4d0 fs/nilfs2/super.c:529
nilfs_fill_super+0x321/0x600 fs/nilfs2/super.c:1074
nilfs_mount+0x67d/0x9a0 fs/nilfs2/super.c:1326
legacy_get_tree+0xef/0x190 fs/fs_context.c:610
vfs_get_tree+0x8c/0x270 fs/super.c:1510
do_new_mount+0x28f/0xae0 fs/namespace.c:3039
do_mount fs/namespace.c:3382 [inline]
__do_sys_mount fs/namespace.c:3591 [inline]
__se_sys_mount+0x2d9/0x3c0 fs/namespace.c:3568
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 4999:
kasan_save_stack mm/kasan/common.c:45 [inline]
kasan_set_track+0x4f/0x70 mm/kasan/common.c:52
kasan_save_free_info+0x2b/0x40 mm/kasan/generic.c:521
____kasan_slab_free+0xd6/0x120 mm/kasan/common.c:236
kasan_slab_free include/linux/kasan.h:162 [inline]
slab_free_hook mm/slub.c:1781 [inline]
slab_free_freelist_hook mm/slub.c:1807 [inline]
slab_free mm/slub.c:3786 [inline]
__kmem_cache_free+0x264/0x3c0 mm/slub.c:3799
nilfs_segctor_destroy fs/nilfs2/segment.c:2775 [inline]
nilfs_detach_log_writer+0x8c1/0xbb0 fs/nilfs2/segment.c:2838
nilfs_put_super+0x4d/0x160 fs/nilfs2/super.c:477
generic_shutdown_super+0x134/0x340 fs/super.c:500
kill_block_super+0x84/0xf0 fs/super.c:1407
deactivate_locked_super+0xa4/0x110 fs/super.c:331
cleanup_mnt+0x426/0x4c0 fs/namespace.c:1177
task_work_run+0x24a/0x300 kernel/task_work.c:179
ptrace_notify+0x2cd/0x380 kernel/signal.c:2369
ptrace_report_syscall include/linux/ptrace.h:411 [inline]
ptrace_report_syscall_exit include/linux/ptrace.h:473 [inline]
syscall_exit_work kernel/entry/common.c:252 [inline]
syscall_exit_to_user_mode_prepare kernel/entry/common.c:279 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:284 [inline]
syscall_exit_to_user_mode+0x157/0x280 kernel/entry/common.c:297
do_syscall_64+0x4d/0xc0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff88801f47f400
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 48 bytes inside of
freed 256-byte region [ffff88801f47f400, ffff88801f47f500)

The buggy address belongs to the physical page:
page:ffffea00007d1f80 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88801f47f600 pfn:0x1f47e
head:ffffea00007d1f80 order:1 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000010200 ffff888012441b40 ffffea00008ccc90 ffffea00007a7510
raw: ffff88801f47f600 000000000010000e 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 9284804112, free_ts 0
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1e6/0x210 mm/page_alloc.c:1731
prep_new_page mm/page_alloc.c:1738 [inline]
get_page_from_freelist+0x321c/0x33a0 mm/page_alloc.c:3502
__alloc_pages+0x255/0x670 mm/page_alloc.c:4768
alloc_page_interleave+0x22/0x1d0 mm/mempolicy.c:2112
alloc_slab_page+0x6a/0x160 mm/slub.c:1851
allocate_slab mm/slub.c:1998 [inline]
new_slab+0x84/0x2f0 mm/slub.c:2051
___slab_alloc+0xa85/0x10a0 mm/slub.c:3192
__slab_alloc mm/slub.c:3291 [inline]
__slab_alloc_node mm/slub.c:3344 [inline]
slab_alloc_node mm/slub.c:3441 [inline]
__kmem_cache_alloc_node+0x1b8/0x290 mm/slub.c:3490
kmalloc_trace+0x2a/0xe0 mm/slab_common.c:1057
kmalloc include/linux/slab.h:559 [inline]
kzalloc include/linux/slab.h:680 [inline]
bus_add_driver+0x163/0x620 drivers/base/bus.c:657
driver_register+0x23a/0x320 drivers/base/driver.c:246
do_one_initcall+0x23d/0x7d0 init/main.c:1246
do_initcall_level+0x157/0x210 init/main.c:1319
do_initcalls+0x3f/0x80 init/main.c:1335
kernel_init_freeable+0x43b/0x5d0 init/main.c:1571
kernel_init+0x1d/0x2a0 init/main.c:1462
page_owner free stack trace missing

Memory state around the buggy address:
ffff88801f47f300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88801f47f380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88801f47f400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88801f47f480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88801f47f500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


---
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[Ryusuke Konishi]

During unmount process of nilfs2, nothing holds nilfs_root structure after
nilfs2 detaches its writer in nilfs_detach_log_writer(). However, since
nilfs_evict_inode() uses nilfs_root for some cleanup operations, it may
cause use-after-free read if inodes are left in "garbage_list" and
released by nilfs_dispose_list() at the end of nilfs_detach_log_writer().

Fix this issue by modifying nilfs_evict_inode() to only clear inode
without additional metadata changes that use nilfs_root if the file system
is degraded to read-only or the writer is detached.

Signed-off-by: Ryusuke Konishi <konishi...@gmail.com>
Reported-by: syzbot+78d449...@syzkaller.appspotmail.com
Closes: https://lkml.kernel.org/r/00000000000099...@google.com
Tested-by: Ryusuke Konishi <konishi...@gmail.com>
Cc: sta...@vger.kernel.org
---
fs/nilfs2/inode.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)

diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index 1310d2d5feb3..a8ce522ac747 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -917,6 +917,7 @@ void nilfs_evict_inode(struct inode *inode)
struct nilfs_transaction_info ti;
struct super_block *sb = inode->i_sb;
struct nilfs_inode_info *ii = NILFS_I(inode);
+ struct the_nilfs *nilfs;
int ret;

if (inode->i_nlink || !ii->i_root || unlikely(is_bad_inode(inode))) {
@@ -929,6 +930,23 @@ void nilfs_evict_inode(struct inode *inode)

truncate_inode_pages_final(&inode->i_data);

+ nilfs = sb->s_fs_info;
+ if (unlikely(sb_rdonly(sb) || !nilfs->ns_writer)) {
+ /*
+ * If this inode is about to be disposed after the file system
+ * has been degraded to read-only due to file system corruption
+ * or after the writer has been detached, do not make any
+ * changes that cause writes, just clear it.
+ * Do this check after read-locking ns_segctor_sem by
+ * nilfs_transaction_begin() in order to avoid a race with
+ * the writer detach operation.
+ */
+ clear_inode(inode);
+ nilfs_clear_inode(inode);
+ nilfs_transaction_abort(sb);
+ return;
+ }
+
/* TODO: some of the following operations may fail. */
nilfs_truncate_bmap(ii, 0);
nilfs_mark_inode_dirty(inode);
--
2.34.1

[Andrew Morton]

On Wed, 10 May 2023 00:29:56 +0900 Ryusuke Konishi <konishi...@gmail.com> wrote:

> During unmount process of nilfs2, nothing holds nilfs_root structure after
> nilfs2 detaches its writer in nilfs_detach_log_writer(). However, since
> nilfs_evict_inode() uses nilfs_root for some cleanup operations, it may
> cause use-after-free read if inodes are left in "garbage_list" and
> released by nilfs_dispose_list() at the end of nilfs_detach_log_writer().
>
> Fix this issue by modifying nilfs_evict_inode() to only clear inode
> without additional metadata changes that use nilfs_root if the file system
> is degraded to read-only or the writer is detached.
>

> ...

>
> --- a/fs/nilfs2/inode.c
> +++ b/fs/nilfs2/inode.c
> @@ -917,6 +917,7 @@ void nilfs_evict_inode(struct inode *inode)
> struct nilfs_transaction_info ti;
> struct super_block *sb = inode->i_sb;
> struct nilfs_inode_info *ii = NILFS_I(inode);
> + struct the_nilfs *nilfs;
> int ret;

`the_nilfs' is unused - I'll zap it.

[Andrew Morton]

argh, sorry, brainfart.