[syzbot] KASAN: use-after-free Read in setup_rw_floppy

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 26291c54e111 Linux 5.17-rc2
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=108fb648700000
kernel config: https://syzkaller.appspot.com/x/.config?x=9bdff1d807acada
dashboard link: https://syzkaller.appspot.com/bug?extid=8e8958586909d62b6840
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8e8958...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in setup_rw_floppy+0x84a/0x9e0 drivers/block/floppy.c:1518
Read of size 1 at addr ffff888026a5fe35 by task kworker/u16:4/3773

CPU: 2 PID: 3773 Comm: kworker/u16:4 Not tainted 5.17.0-rc2-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
Workqueue: floppy fd_timer_workfn
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_address_description.constprop.0.cold+0x8d/0x303 mm/kasan/report.c:255
__kasan_report mm/kasan/report.c:442 [inline]
kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
setup_rw_floppy+0x84a/0x9e0 drivers/block/floppy.c:1518
seek_floppy drivers/block/floppy.c:1639 [inline]
floppy_ready drivers/block/floppy.c:1956 [inline]
floppy_ready+0x345/0x1850 drivers/block/floppy.c:1927
process_one_work+0x9ac/0x1650 kernel/workqueue.c:2307
worker_thread+0x657/0x1110 kernel/workqueue.c:2454
kthread+0x2e9/0x3a0 kernel/kthread.c:377
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>

Allocated by task 16034:
kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
kasan_set_track mm/kasan/common.c:45 [inline]
set_alloc_info mm/kasan/common.c:436 [inline]
____kasan_kmalloc mm/kasan/common.c:515 [inline]
____kasan_kmalloc mm/kasan/common.c:474 [inline]
__kasan_kmalloc+0xa6/0xd0 mm/kasan/common.c:524
kasan_kmalloc include/linux/kasan.h:270 [inline]
kmem_cache_alloc_trace+0x1ea/0x4a0 mm/slab.c:3567
kmalloc include/linux/slab.h:581 [inline]
raw_cmd_copyin drivers/block/floppy.c:3095 [inline]
raw_cmd_ioctl drivers/block/floppy.c:3162 [inline]
fd_locked_ioctl+0x100e/0x2830 drivers/block/floppy.c:3530
fd_ioctl+0x35/0x50 drivers/block/floppy.c:3557
blkdev_ioctl+0x37a/0x800 block/ioctl.c:588
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 16034:
kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
kasan_set_track+0x21/0x30 mm/kasan/common.c:45
kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
____kasan_slab_free mm/kasan/common.c:366 [inline]
____kasan_slab_free mm/kasan/common.c:328 [inline]
__kasan_slab_free+0xee/0x130 mm/kasan/common.c:374
kasan_slab_free include/linux/kasan.h:236 [inline]
__cache_free mm/slab.c:3437 [inline]
kfree+0xf6/0x290 mm/slab.c:3794
raw_cmd_free+0x8a/0x1c0 drivers/block/floppy.c:3079
raw_cmd_ioctl drivers/block/floppy.c:3182 [inline]
fd_locked_ioctl+0x207e/0x2830 drivers/block/floppy.c:3530
fd_ioctl+0x35/0x50 drivers/block/floppy.c:3557
blkdev_ioctl+0x37a/0x800 block/ioctl.c:588
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

Last potentially related work creation:
kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
__kasan_record_aux_stack+0x7e/0x90 mm/kasan/generic.c:348
kvfree_call_rcu+0x74/0x990 kernel/rcu/tree.c:3591
__hw_addr_flush+0x152/0x240 net/core/dev_addr_lists.c:488
dev_addr_flush+0x1d/0x50 net/core/dev_addr_lists.c:533
free_netdev+0x1f5/0x5b0 net/core/dev.c:10283
netdev_run_todo+0x8a0/0xaa0 net/core/dev.c:9964
ip_tunnel_delete_nets+0x3a4/0x5b0 net/ipv4/ip_tunnel.c:1124
ops_exit_list+0x125/0x170 net/core/net_namespace.c:173
cleanup_net+0x4ea/0xb00 net/core/net_namespace.c:597
process_one_work+0x9ac/0x1650 kernel/workqueue.c:2307
worker_thread+0x657/0x1110 kernel/workqueue.c:2454
kthread+0x2e9/0x3a0 kernel/kthread.c:377
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Second to last potentially related work creation:
kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
__kasan_record_aux_stack+0x7e/0x90 mm/kasan/generic.c:348
kvfree_call_rcu+0x74/0x990 kernel/rcu/tree.c:3591
drop_sysctl_table+0x3c0/0x4e0 fs/proc/proc_sysctl.c:1705
unregister_sysctl_table fs/proc/proc_sysctl.c:1743 [inline]
unregister_sysctl_table+0xc0/0x190 fs/proc/proc_sysctl.c:1718
mpls_dev_sysctl_unregister net/mpls/af_mpls.c:1441 [inline]
mpls_dev_notify+0x4fb/0x8a0 net/mpls/af_mpls.c:1654
notifier_call_chain+0xb5/0x200 kernel/notifier.c:84
call_netdevice_notifiers_info+0xb5/0x130 net/core/dev.c:1919
call_netdevice_notifiers_extack net/core/dev.c:1931 [inline]
call_netdevice_notifiers net/core/dev.c:1945 [inline]
unregister_netdevice_many+0x964/0x1850 net/core/dev.c:10415
ip_tunnel_delete_nets+0x39f/0x5b0 net/ipv4/ip_tunnel.c:1123
ops_exit_list+0x125/0x170 net/core/net_namespace.c:173
cleanup_net+0x4ea/0xb00 net/core/net_namespace.c:597
process_one_work+0x9ac/0x1650 kernel/workqueue.c:2307
worker_thread+0x657/0x1110 kernel/workqueue.c:2454
kthread+0x2e9/0x3a0 kernel/kthread.c:377
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

The buggy address belongs to the object at ffff888026a5fe00
which belongs to the cache kmalloc-128 of size 128
The buggy address is located 53 bytes inside of
128-byte region [ffff888026a5fe00, ffff888026a5fe80)
The buggy address belongs to the page:
page:ffffea00009a97c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x26a5f
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 ffffea000083f648 ffffea0000657d48 ffff888010c40400
raw: 0000000000000000 ffff888026a5f000 0000000100000010 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x242220(__GFP_HIGH|__GFP_ATOMIC|__GFP_NOWARN|__GFP_COMP|__GFP_THISNODE), pid 7589, ts 856054219165, free_ts 610363186592
prep_new_page mm/page_alloc.c:2434 [inline]
get_page_from_freelist+0xa72/0x2f50 mm/page_alloc.c:4165
__alloc_pages_slowpath.constprop.0+0x2eb/0x20d0 mm/page_alloc.c:4934
__alloc_pages+0x412/0x500 mm/page_alloc.c:5402
__alloc_pages_node include/linux/gfp.h:572 [inline]
kmem_getpages mm/slab.c:1378 [inline]
cache_grow_begin+0x75/0x350 mm/slab.c:2584
cache_alloc_refill+0x27f/0x380 mm/slab.c:2957
____cache_alloc mm/slab.c:3040 [inline]
____cache_alloc mm/slab.c:3023 [inline]
__do_cache_alloc mm/slab.c:3267 [inline]
slab_alloc mm/slab.c:3308 [inline]
kmem_cache_alloc_trace+0x380/0x4a0 mm/slab.c:3565
kmalloc include/linux/slab.h:581 [inline]
__hw_addr_create net/core/dev_addr_lists.c:58 [inline]
__hw_addr_add_ex+0x22d/0x7e0 net/core/dev_addr_lists.c:116
__hw_addr_add net/core/dev_addr_lists.c:133 [inline]
dev_addr_init+0x13a/0x220 net/core/dev_addr_lists.c:556
alloc_netdev_mqs+0x280/0x1070 net/core/dev.c:10180
ip6gre_init_net+0x1b6/0x630 net/ipv6/ip6_gre.c:1593
ops_init+0xaf/0x470 net/core/net_namespace.c:140
setup_net+0x554/0xbb0 net/core/net_namespace.c:330
copy_net_ns+0x318/0x760 net/core/net_namespace.c:474
create_new_namespaces+0x3f6/0xb20 kernel/nsproxy.c:110
unshare_nsproxy_namespaces+0xc1/0x1f0 kernel/nsproxy.c:226
ksys_unshare+0x445/0x920 kernel/fork.c:3048
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1352 [inline]
free_pcp_prepare+0x374/0x870 mm/page_alloc.c:1404
free_unref_page_prepare mm/page_alloc.c:3325 [inline]
free_unref_page_list+0x1a9/0xfa0 mm/page_alloc.c:3441
release_pages+0x317/0x1220 mm/swap.c:980
tlb_batch_pages_flush mm/mmu_gather.c:50 [inline]
tlb_flush_mmu_free mm/mmu_gather.c:243 [inline]
tlb_flush_mmu mm/mmu_gather.c:250 [inline]
tlb_finish_mmu+0x165/0x8c0 mm/mmu_gather.c:341
exit_mmap+0x21b/0x670 mm/mmap.c:3180
__mmput+0x122/0x4b0 kernel/fork.c:1114
mmput+0x56/0x60 kernel/fork.c:1135
exit_mm kernel/exit.c:507 [inline]
do_exit+0xa3c/0x2a30 kernel/exit.c:793
do_group_exit+0xd2/0x2f0 kernel/exit.c:935
__do_sys_exit_group kernel/exit.c:946 [inline]
__se_sys_exit_group kernel/exit.c:944 [inline]
__x64_sys_exit_group+0x3a/0x50 kernel/exit.c:944
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

Memory state around the buggy address:
ffff888026a5fd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888026a5fd80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888026a5fe00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888026a5fe80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888026a5ff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc
==================================================================


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