Re: [syzbot] KASAN: use-after-free Read in disk_part_iter_next (2)

From: syzbot
Date: Wed Mar 24 2021 - 06:02:17 EST

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In reply to: Christoph Hellwig: "Re: [syzbot] KASAN: use-after-free Read in disk_part_iter_next (2)"
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Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: use-after-free Read in bdgrab

==================================================================
BUG: KASAN: use-after-free in bdgrab+0x4c/0x50 fs/block_dev.c:929
Read of size 8 at addr ffff88801639a2a8 by task syz-executor.0/10133

CPU: 1 PID: 10133 Comm: syz-executor.0 Not tainted 5.12.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x141/0x1d7 lib/dump_stack.c:120
print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:232
__kasan_report mm/kasan/report.c:399 [inline]
kasan_report.cold+0x7c/0xd8 mm/kasan/report.c:416
bdgrab+0x4c/0x50 fs/block_dev.c:929
first_partition+0xfa/0x230 block/partitions/core.c:538
blk_drop_partitions+0xb5/0xf0 block/partitions/core.c:555
bdev_disk_changed+0x238/0x430 fs/block_dev.c:1237
__loop_clr_fd+0x7c7/0xff0 drivers/block/loop.c:1271
lo_release+0x1ac/0x1f0 drivers/block/loop.c:1923
__blkdev_put+0x54e/0x800 fs/block_dev.c:1579
blkdev_put+0x92/0x580 fs/block_dev.c:1632
blkdev_close+0x8c/0xb0 fs/block_dev.c:1640
__fput+0x288/0x920 fs/file_table.c:280
task_work_run+0xdd/0x1a0 kernel/task_work.c:140
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
exit_to_user_mode_prepare+0x249/0x250 kernel/entry/common.c:208
__syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x41926b
Code: 0f 05 48 3d 00 f0 ff ff 77 45 c3 0f 1f 40 00 48 83 ec 18 89 7c 24 0c e8 63 fc ff ff 8b 7c 24 0c 41 89 c0 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 44 89 c7 89 44 24 0c e8 a1 fc ff ff 8b 44
RSP: 002b:00007fff13e6a990 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 000000000041926b
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000003
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000001b2fb20070
R10: 0000000000000000 R11: 0000000000000293 R12: 000000000056c9e0
R13: 000000000056c9e0 R14: 000000000056bf60 R15: 000000000001383c

Allocated by task 10136:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:427 [inline]
__kasan_slab_alloc+0x75/0x90 mm/kasan/common.c:460
kasan_slab_alloc include/linux/kasan.h:223 [inline]
slab_post_alloc_hook mm/slab.h:516 [inline]
slab_alloc_node mm/slub.c:2907 [inline]
slab_alloc mm/slub.c:2915 [inline]
kmem_cache_alloc+0x155/0x370 mm/slub.c:2920
bdev_alloc_inode+0x18/0x80 fs/block_dev.c:786
alloc_inode+0x61/0x230 fs/inode.c:234
new_inode_pseudo fs/inode.c:928 [inline]
new_inode+0x27/0x2f0 fs/inode.c:957
bdev_alloc+0x20/0x2f0 fs/block_dev.c:876
add_partition+0x1ab/0x8a0 block/partitions/core.c:348
bdev_add_partition+0xb6/0x130 block/partitions/core.c:451
blkpg_do_ioctl+0x2d0/0x340 block/ioctl.c:43
blkpg_ioctl block/ioctl.c:60 [inline]
blkdev_ioctl+0x577/0x6d0 block/ioctl.c:548
block_ioctl+0xf9/0x140 fs/block_dev.c:1658
vfs_ioctl fs/ioctl.c:48 [inline]
__do_sys_ioctl fs/ioctl.c:753 [inline]
__se_sys_ioctl fs/ioctl.c:739 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 4849:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:357
____kasan_slab_free mm/kasan/common.c:360 [inline]
____kasan_slab_free mm/kasan/common.c:325 [inline]
__kasan_slab_free+0xf5/0x130 mm/kasan/common.c:367
kasan_slab_free include/linux/kasan.h:199 [inline]
slab_free_hook mm/slub.c:1562 [inline]
slab_free_freelist_hook+0x92/0x210 mm/slub.c:1600
slab_free mm/slub.c:3161 [inline]
kmem_cache_free+0x8a/0x740 mm/slub.c:3177
i_callback+0x3f/0x70 fs/inode.c:223
rcu_do_batch kernel/rcu/tree.c:2559 [inline]
rcu_core+0x74a/0x12f0 kernel/rcu/tree.c:2794
__do_softirq+0x29b/0x9f6 kernel/softirq.c:345

Last potentially related work creation:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
kasan_record_aux_stack+0xe5/0x110 mm/kasan/generic.c:345
__call_rcu kernel/rcu/tree.c:3039 [inline]
call_rcu+0xb1/0x740 kernel/rcu/tree.c:3114
destroy_inode+0x129/0x1b0 fs/inode.c:289
iput_final fs/inode.c:1654 [inline]
iput.part.0+0x57e/0x810 fs/inode.c:1680
iput+0x58/0x70 fs/inode.c:1670
blk_drop_partitions+0x9d/0xf0 block/partitions/core.c:557
bdev_disk_changed+0x238/0x430 fs/block_dev.c:1237
loop_reread_partitions+0x29/0x50 drivers/block/loop.c:655
loop_set_status+0x704/0x1050 drivers/block/loop.c:1418
loop_set_status64 drivers/block/loop.c:1538 [inline]
lo_ioctl+0x4ca/0x1620 drivers/block/loop.c:1706
blkdev_ioctl+0x2a1/0x6d0 block/ioctl.c:583
block_ioctl+0xf9/0x140 fs/block_dev.c:1658
vfs_ioctl fs/ioctl.c:48 [inline]
__do_sys_ioctl fs/ioctl.c:753 [inline]
__se_sys_ioctl fs/ioctl.c:739 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xae

The buggy address belongs to the object at ffff88801639a280
which belongs to the cache bdev_cache of size 2792
The buggy address is located 40 bytes inside of
2792-byte region [ffff88801639a280, ffff88801639ad68)
The buggy address belongs to the page:
page:ffffea000058e600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x16398
head:ffffea000058e600 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff8880101bdb40
raw: 0000000000000000 00000000800b000b 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88801639a180: 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc
ffff88801639a200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88801639a280: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88801639a300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88801639a380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Tested on:

commit: 7b997e8f block: simplify partition removal
git tree: git://git.infradead.org/users/hch/block.git part-iter-fix
console output: https://syzkaller.appspot.com/x/log.txt?x=14d147aed00000
kernel config: https://syzkaller.appspot.com/x/.config?x=c000f42ea85d0228
dashboard link: https://syzkaller.appspot.com/bug?extid=8fede7e30c7cee0de139
compiler:

Next message: Daniel Vetter: "Re: [PATCH] i915_vma: Rename vma_lookup to i915_vma_lookup"
Previous message: Daniel Vetter: "Re: [RFC PATCH 1/2] mm,drm/ttm: Block fast GUP to TTM huge pages"
In reply to: Christoph Hellwig: "Re: [syzbot] KASAN: use-after-free Read in disk_part_iter_next (2)"
Next in thread: Ming Lei: "Re: [syzbot] KASAN: use-after-free Read in disk_part_iter_next (2)"
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