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BUG: KASAN: slab-out-of-bounds in mpol_parse_str+0x87b/0xa50 mm/mempolicy.c:2922
Write of size 1 at addr ffff8880983ee33f by task syz-executor.4/19745

CPU: 0 PID: 19745 Comm: syz-executor.4 Not tainted 5.5.0-rc5-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+0x197/0x210 lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
 __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
 kasan_report+0x12/0x20 mm/kasan/common.c:639
 __asan_report_store1_noabort+0x17/0x20 mm/kasan/generic_report.c:137
 mpol_parse_str+0x87b/0xa50 mm/mempolicy.c:2922
 shmem_parse_one+0x71e/0xa40 mm/shmem.c:3472
 vfs_parse_fs_param+0x2ca/0x540 fs/fs_context.c:145
 vfs_parse_fs_string+0x105/0x170 fs/fs_context.c:188
 shmem_parse_options+0x168/0x250 mm/shmem.c:3522
 parse_monolithic_mount_data+0x69/0x90 fs/fs_context.c:704
 do_new_mount fs/namespace.c:2818 [inline]
 do_mount+0x1310/0x1b50 fs/namespace.c:3142
 __do_sys_mount fs/namespace.c:3351 [inline]
 __se_sys_mount fs/namespace.c:3328 [inline]
 __x64_sys_mount+0x192/0x230 fs/namespace.c:3328
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45d99a
Code: b8 a6 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 4d 8c fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 2a 8c fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007fee9eb11a68 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000007 RCX: 000000000045d99a
RDX: 00007fee9eb11ae0 RSI: 00000000200000c0 RDI: 00007fee9eb11b00
RBP: 000000000075bf20 R08: 00007fee9eb11b40 R09: 00007fee9eb11ae0
R10: 0000000000000000 R11: 0000000000000202 R12: 00007fee9eb126d4
R13: 00000000004cbf00 R14: 00000000004e6ba8 R15: 00000000ffffffff

Allocated by task 14563:
 save_stack+0x23/0x90 mm/kasan/common.c:72
 set_track mm/kasan/common.c:80 [inline]
 __kasan_kmalloc mm/kasan/common.c:513 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:486
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:527
 __do_kmalloc mm/slab.c:3656 [inline]
 __kmalloc+0x163/0x770 mm/slab.c:3665
 kmalloc include/linux/slab.h:561 [inline]
 context_struct_to_string security/selinux/ss/services.c:1238 [inline]
 context_struct_to_string+0x368/0x950 security/selinux/ss/services.c:1208
 security_sid_to_context_core.isra.0+0x2fb/0x390 security/selinux/ss/services.c:1318
 security_sid_to_context_force+0x3a/0x50 security/selinux/ss/services.c:1347
 selinux_inode_init_security+0x555/0x7b0 security/selinux/hooks.c:2931
 security_inode_init_security security/security.c:985 [inline]
 security_inode_init_security+0x1ad/0x3b0 security/security.c:969
 shmem_mknod+0xc9/0x1f0 mm/shmem.c:2889
 shmem_create+0x2b/0x40 mm/shmem.c:2944
 lookup_open+0x12d5/0x1a90 fs/namei.c:3241
 do_last fs/namei.c:3331 [inline]
 path_openat+0x14a2/0x4500 fs/namei.c:3537
 do_filp_open+0x1a1/0x280 fs/namei.c:3567
 do_sys_open+0x3fe/0x5d0 fs/open.c:1097
 __do_sys_open fs/open.c:1115 [inline]
 __se_sys_open fs/open.c:1110 [inline]
 __x64_sys_open+0x7e/0xc0 fs/open.c:1110
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 14563:
 save_stack+0x23/0x90 mm/kasan/common.c:72
 set_track mm/kasan/common.c:80 [inline]
 kasan_set_free_info mm/kasan/common.c:335 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:474
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:483
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x10a/0x2c0 mm/slab.c:3757
 security_inode_init_security security/security.c:999 [inline]
 security_inode_init_security+0x1ed/0x3b0 security/security.c:969
 shmem_mknod+0xc9/0x1f0 mm/shmem.c:2889
 shmem_create+0x2b/0x40 mm/shmem.c:2944
 lookup_open+0x12d5/0x1a90 fs/namei.c:3241
 do_last fs/namei.c:3331 [inline]
 path_openat+0x14a2/0x4500 fs/namei.c:3537
 do_filp_open+0x1a1/0x280 fs/namei.c:3567
 do_sys_open+0x3fe/0x5d0 fs/open.c:1097
 __do_sys_open fs/open.c:1115 [inline]
 __se_sys_open fs/open.c:1110 [inline]
 __x64_sys_open+0x7e/0xc0 fs/open.c:1110
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880983ee300
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 31 bytes to the right of
 32-byte region [ffff8880983ee300, ffff8880983ee320)
The buggy address belongs to the page:
page:ffffea000260fb80 refcount:1 mapcount:0 mapping:ffff8880aa4001c0 index:0xffff8880983eefc1
raw: 00fffe0000000200 ffffea0002737ac8 ffffea0002786248 ffff8880aa4001c0
raw: ffff8880983eefc1 ffff8880983ee000 000000010000003f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880983ee200: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
 ffff8880983ee280: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
>ffff8880983ee300: fb fb fb fb fc fc fc fc 00 05 fc fc fc fc fc fc
                                        ^
 ffff8880983ee380: fb fb fb fb fc fc fc fc 00 00 fc fc fc fc fc fc
 ffff8880983ee400: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
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