KASAN: use-after-free Read in cgroup_throttle_swaprate

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    7ae77150 Merge tag 'powerpc-5.8-1' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11d65615100000
kernel config:  https://syzkaller.appspot.com/x/.config?x=be4578b3f1083656
dashboard link: https://syzkaller.appspot.com/bug?extid=5e421ac7ea78f893184b
compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+5e421ac7ea78f893184b@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: use-after-free in atomic_read include/asm-generic/atomic-instrumented.h:26 [inline]
BUG: KASAN: use-after-free in blk_cgroup_congested include/linux/blk-cgroup.h:288 [inline]
BUG: KASAN: use-after-free in cgroup_throttle_swaprate+0x268/0x4f0 mm/swapfile.c:3799
Read of size 4 at addr ffff888098690d80 by task syz-executor.1/11017

CPU: 0 PID: 11017 Comm: syz-executor.1 Not tainted 5.7.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1e9/0x30e lib/dump_stack.c:118
 print_address_description+0x66/0x5a0 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report+0x132/0x1d0 mm/kasan/report.c:530
 check_memory_region_inline mm/kasan/generic.c:183 [inline]
 check_memory_region+0x2b5/0x2f0 mm/kasan/generic.c:192
 atomic_read include/asm-generic/atomic-instrumented.h:26 [inline]
 blk_cgroup_congested include/linux/blk-cgroup.h:288 [inline]
 cgroup_throttle_swaprate+0x268/0x4f0 mm/swapfile.c:3799
 wp_page_copy+0x29c/0x1ff0 mm/memory.c:2680
 do_wp_page+0x750/0x1810 mm/memory.c:2919
 handle_pte_fault mm/memory.c:4233 [inline]
 __handle_mm_fault mm/memory.c:4347 [inline]
 handle_mm_fault+0x23fc/0x2910 mm/memory.c:4384
 faultin_page mm/gup.c:888 [inline]
 __get_user_pages+0xbf5/0x16f0 mm/gup.c:1114
 __get_user_pages_locked mm/gup.c:1307 [inline]
 __get_user_pages_remote+0x130/0x680 mm/gup.c:1858
 process_vm_rw_single_vec mm/process_vm_access.c:108 [inline]
 process_vm_rw_core+0x458/0x990 mm/process_vm_access.c:218
 process_vm_rw+0x1b7/0x270 mm/process_vm_access.c:286
 __do_sys_process_vm_writev mm/process_vm_access.c:308 [inline]
 __se_sys_process_vm_writev mm/process_vm_access.c:303 [inline]
 __x64_sys_process_vm_writev+0xdc/0xf0 mm/process_vm_access.c:303
 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x45ca59
Code: 0d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 db b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f34c4af9c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000137
RAX: ffffffffffffffda RBX: 00000000004fb1a0 RCX: 000000000045ca59
RDX: 1000000000000005 RSI: 0000000020000000 RDI: 0000000000000108
RBP: 000000000078bfa0 R08: 000000000000023a R09: 0000000000000000
R10: 0000000020000180 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000087c R14: 00000000004cb674 R15: 00007f34c4afa6d4

Allocated by task 1:
 save_stack mm/kasan/common.c:48 [inline]
 set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc+0x103/0x140 mm/kasan/common.c:494
 kmem_cache_alloc_trace+0x234/0x300 mm/slab.c:3551
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:669 [inline]
 cgroup1_root_to_use kernel/cgroup/cgroup-v1.c:1183 [inline]
 cgroup1_get_tree+0x747/0xae0 kernel/cgroup/cgroup-v1.c:1207
 vfs_get_tree+0x88/0x270 fs/super.c:1547
 do_new_mount fs/namespace.c:2874 [inline]
 do_mount+0x17e8/0x2900 fs/namespace.c:3199
 __do_sys_mount fs/namespace.c:3409 [inline]
 __se_sys_mount+0xd3/0x100 fs/namespace.c:3386
 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3

Freed by task 17:
 save_stack mm/kasan/common.c:48 [inline]
 set_track mm/kasan/common.c:56 [inline]
 kasan_set_free_info mm/kasan/common.c:316 [inline]
 __kasan_slab_free+0x114/0x170 mm/kasan/common.c:455
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x10a/0x220 mm/slab.c:3757
 process_one_work+0x76e/0xfd0 kernel/workqueue.c:2268
 worker_thread+0xa7f/0x1450 kernel/workqueue.c:2414
 kthread+0x353/0x380 kernel/kthread.c:268
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:351

The buggy address belongs to the object at ffff888098690000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 3456 bytes inside of
 8192-byte region [ffff888098690000, ffff888098692000)
The buggy address belongs to the page:
page:ffffea000261a400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 head:ffffea000261a400 order:2 compound_mapcount:0 compound_pincount:0
flags: 0xfffe0000010200(slab|head)
raw: 00fffe0000010200 ffffea0002619a08 ffffea000261ae08 ffff8880aa4021c0
raw: 0000000000000000 ffff888098690000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888098690c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888098690d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888098690d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888098690e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888098690e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


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