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BUG: KASAN: slab-use-after-free in strcmp+0x70/0xc0 lib/string.c:272
Read of size 1 at addr ffff88812c1d5760 by task syz.4.3980/4386

CPU: 1 UID: 0 PID: 4386 Comm: syz.4.3980 Not tainted syzkaller #0 45964a5c932d45c81e53484b258bbb49855afb35
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0x140/0x1c0 lib/dump_stack.c:120
 print_address_description+0x71/0x210 mm/kasan/report.c:377
 print_report+0x4a/0x70 mm/kasan/report.c:481
 kasan_report+0x162/0x1a0 mm/kasan/report.c:594
 __asan_report_load1_noabort+0x18/0x20 mm/kasan/report_generic.c:378
 strcmp+0x70/0xc0 lib/string.c:272
 algorithm_params_store+0x425/0x790 drivers/block/zram/zram_drv.c:2109
 dev_attr_store+0x76/0xa0 drivers/base/core.c:2440
 sysfs_kf_write+0x141/0x160 fs/sysfs/file.c:136
 kernfs_fop_write_iter+0x316/0x510 fs/kernfs/file.c:352
 new_sync_write fs/read_write.c:591 [inline]
 vfs_write+0x762/0xfd0 fs/read_write.c:684
 ksys_write+0x145/0x260 fs/read_write.c:737
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x7f/0x90 fs/read_write.c:746
 x64_sys_call+0x271c/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:47 [inline]
 do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7ff936b9de99
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffeb90dca18 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007ff936e25fa0 RCX: 00007ff936b9de99
RDX: 000000000000001d RSI: 0000200000000400 RDI: 0000000000000004
RBP: 00007ff936c33eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff936e25fac R14: 00007ff936e25fa0 R15: 00007ff936e25fa0
 </TASK>

Allocated by task 4386:
 kasan_save_stack mm/kasan/common.c:49 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:70
 kasan_save_alloc_info+0x3a/0x50 mm/kasan/generic.c:565
 poison_kmalloc_redzone mm/kasan/common.c:379 [inline]
 __kasan_kmalloc+0x96/0xb0 mm/kasan/common.c:396
 kasan_kmalloc include/linux/kasan.h:261 [inline]
 __do_kmalloc_node mm/slub.c:4395 [inline]
 __kmalloc_node_track_caller_noprof+0x24e/0x4f0 mm/slub.c:4414
 kstrdup+0x4d/0x130 mm/util.c:70
 __comp_algorithm_store+0x5c/0x250 drivers/block/zram/zram_drv.c:2004
 comp_algorithm_store+0x6e/0xb0 drivers/block/zram/zram_drv.c:2140
 dev_attr_store+0x76/0xa0 drivers/base/core.c:2440
 sysfs_kf_write+0x141/0x160 fs/sysfs/file.c:136
 kernfs_fop_write_iter+0x316/0x510 fs/kernfs/file.c:352
 new_sync_write fs/read_write.c:591 [inline]
 vfs_write+0x762/0xfd0 fs/read_write.c:684
 ksys_write+0x145/0x260 fs/read_write.c:737
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x7f/0x90 fs/read_write.c:746
 x64_sys_call+0x271c/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:47 [inline]
 do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Freed by task 4385:
 kasan_save_stack mm/kasan/common.c:49 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:70
 kasan_save_free_info+0x44/0x50 mm/kasan/generic.c:579
 poison_slab_object mm/kasan/common.c:249 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:266
 kasan_slab_free include/linux/kasan.h:234 [inline]
 slab_free_hook mm/slub.c:2445 [inline]
 slab_free mm/slub.c:4714 [inline]
 kfree+0x158/0x440 mm/slub.c:4875
 comp_algorithm_set drivers/block/zram/zram_drv.c:1979 [inline]
 __comp_algorithm_store+0x190/0x250 drivers/block/zram/zram_drv.c:2025
 comp_algorithm_store+0x6e/0xb0 drivers/block/zram/zram_drv.c:2140
 dev_attr_store+0x76/0xa0 drivers/base/core.c:2440
 sysfs_kf_write+0x141/0x160 fs/sysfs/file.c:136
 kernfs_fop_write_iter+0x316/0x510 fs/kernfs/file.c:352
 new_sync_write fs/read_write.c:591 [inline]
 vfs_write+0x762/0xfd0 fs/read_write.c:684
 ksys_write+0x145/0x260 fs/read_write.c:737
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x7f/0x90 fs/read_write.c:746
 x64_sys_call+0x271c/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:47 [inline]
 do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

The buggy address belongs to the object at ffff88812c1d5760
 which belongs to the cache kmalloc-8 of size 8
The buggy address is located 0 bytes inside of
 freed 8-byte region [ffff88812c1d5760, ffff88812c1d5768)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88812c1d54e0 pfn:0x12c1d5
flags: 0x4000000000000000(zone=1)
page_type: f5(slab)
raw: 4000000000000000 ffff888100041500 ffffea0004279740 dead000000000002
raw: ffff88812c1d54e0 000000008080006f 00000001f5000000 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 0x152cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 378, tgid 378 (syz-executor), ts 39333964508, free_ts 39333933595
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook+0x37d/0x3b0 mm/page_alloc.c:1863
 prep_new_page+0x2d/0x180 mm/page_alloc.c:1871
 get_page_from_freelist+0x4aea/0x4ba0 mm/page_alloc.c:3948
 __alloc_pages_noprof+0x35a/0x7e0 mm/page_alloc.c:5315
 alloc_slab_page+0x6b/0x1e0 mm/slub.c:-1
 allocate_slab+0x69/0x430 mm/slub.c:2687
 new_slab mm/slub.c:2741 [inline]
 ___slab_alloc+0x591/0x8c0 mm/slub.c:3934
 __slab_alloc mm/slub.c:4025 [inline]
 __slab_alloc_node mm/slub.c:4078 [inline]
 slab_alloc_node mm/slub.c:4239 [inline]
 __do_kmalloc_node mm/slub.c:4394 [inline]
 __kmalloc_node_noprof+0x2e7/0x500 mm/slub.c:4401
 kmalloc_node_noprof include/linux/slab.h:908 [inline]
 __vmalloc_area_node mm/vmalloc.c:3674 [inline]
 __vmalloc_node_range_noprof+0x529/0x1300 mm/vmalloc.c:3878
 __vmalloc_node_noprof mm/vmalloc.c:3949 [inline]
 vzalloc_noprof+0x103/0x1d0 mm/vmalloc.c:4022
 alloc_counters+0x75/0x520 net/ipv4/netfilter/ip_tables.c:799
 copy_entries_to_user net/ipv4/netfilter/ip_tables.c:821 [inline]
 get_entries net/ipv4/netfilter/ip_tables.c:1022 [inline]
 do_ipt_get_ctl+0xab5/0x1210 net/ipv4/netfilter/ip_tables.c:1668
 nf_getsockopt+0x28b/0x2b0 net/netfilter/nf_sockopt.c:116
 ip_getsockopt+0x15b/0x200 net/ipv4/ip_sockglue.c:1777
 tcp_getsockopt+0x103/0x130 net/ipv4/tcp.c:4705
 sock_common_getsockopt+0xb2/0xd0 net/core/sock.c:3831
page last free pid 378 tgid 378 stack trace:
 reset_page_owner include/linux/page_owner.h:28 [inline]
 free_pages_prepare mm/page_alloc.c:1390 [inline]
 free_unref_page+0xbb8/0xf70 mm/page_alloc.c:2876
 __free_pages+0x6b/0x3b0 mm/page_alloc.c:5402
 vfree+0x3ea/0x5b0 mm/vmalloc.c:3410
 copy_entries_to_user net/ipv4/netfilter/ip_tables.c:866 [inline]
 get_entries net/ipv4/netfilter/ip_tables.c:1022 [inline]
 do_ipt_get_ctl+0xef6/0x1210 net/ipv4/netfilter/ip_tables.c:1668
 nf_getsockopt+0x28b/0x2b0 net/netfilter/nf_sockopt.c:116
 ip_getsockopt+0x15b/0x200 net/ipv4/ip_sockglue.c:1777
 tcp_getsockopt+0x103/0x130 net/ipv4/tcp.c:4705
 sock_common_getsockopt+0xb2/0xd0 net/core/sock.c:3831
 do_sock_getsockopt+0x3a4/0x6c0 net/socket.c:2398
 __sys_getsockopt net/socket.c:2427 [inline]
 __do_sys_getsockopt net/socket.c:2437 [inline]
 __se_sys_getsockopt net/socket.c:2434 [inline]
 __x64_sys_getsockopt+0x1d4/0x280 net/socket.c:2434
 x64_sys_call+0x10db/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:56
 do_syscall_x64 arch/x86/entry/common.c:47 [inline]
 do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Memory state around the buggy address:
 ffff88812c1d5600: fa fc fc fc fa fc fc fc fa fc fc fc fa fc fc fc
 ffff88812c1d5680: fa fc fc fc fa fc fc fc fa fc fc fc fa fc fc fc
>ffff88812c1d5700: fa fc fc fc fa fc fc fc fa fc fc fc fa fc fc fc
                                                       ^
 ffff88812c1d5780: fa fc fc fc fa fc fc fc fa fc fc fc fa fc fc fc
 ffff88812c1d5800: fa fc fc fc fa fc fc fc fa fc fc fc fa fc fc fc
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