================================================================== BUG: KASAN: use-after-free in css_task_iter_advance+0x49b/0x540 kernel/cgroup/cgroup.c:4507 Read of size 4 at addr ffff88808a9d2fdc by task syz-executor.3/12035 CPU: 0 PID: 12035 Comm: syz-executor.3 Not tainted 5.2.0-rc3-next-20190607 #11 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+0x172/0x1f0 lib/dump_stack.c:113 print_address_description.cold+0xd4/0x306 mm/kasan/report.c:351 __kasan_report.cold+0x1b/0x36 mm/kasan/report.c:482 kasan_report+0x12/0x20 mm/kasan/common.c:614 __asan_report_load4_noabort+0x14/0x20 mm/kasan/generic_report.c:131 css_task_iter_advance+0x49b/0x540 kernel/cgroup/cgroup.c:4507 css_task_iter_start+0x18b/0x230 kernel/cgroup/cgroup.c:4543 pidlist_array_load+0x181/0xa80 kernel/cgroup/cgroup-v1.c:372 cgroup_pidlist_start+0x37e/0x4c0 kernel/cgroup/cgroup-v1.c:442 cgroup_seqfile_start+0xa4/0xd0 kernel/cgroup/cgroup.c:3752 kernfs_seq_start+0xdc/0x190 fs/kernfs/file.c:118 seq_read+0x2a7/0x1110 fs/seq_file.c:224 kernfs_fop_read+0xed/0x560 fs/kernfs/file.c:252 do_loop_readv_writev fs/read_write.c:714 [inline] do_loop_readv_writev fs/read_write.c:701 [inline] do_iter_read+0x4a4/0x660 fs/read_write.c:935 vfs_readv+0xf0/0x160 fs/read_write.c:997 do_preadv+0x1c4/0x280 fs/read_write.c:1089 __do_sys_preadv fs/read_write.c:1139 [inline] __se_sys_preadv fs/read_write.c:1134 [inline] __x64_sys_preadv+0x9a/0xf0 fs/read_write.c:1134 do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x459279 Code: fd 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 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f4915310c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000127 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000459279 RDX: 10000000000000f3 RSI: 0000000020000480 RDI: 0000000000000004 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f49153116d4 R13: 00000000004c6376 R14: 00000000004dae78 R15: 00000000ffffffff Allocated by task 11221: save_stack+0x23/0x90 mm/kasan/common.c:71 set_track mm/kasan/common.c:79 [inline] __kasan_kmalloc mm/kasan/common.c:489 [inline] __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:462 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:503 __do_kmalloc mm/slab.c:3654 [inline] __kmalloc+0x15c/0x740 mm/slab.c:3663 kmalloc include/linux/slab.h:552 [inline] tomoyo_realpath_from_path+0xcd/0x7a0 security/tomoyo/realpath.c:277 tomoyo_get_realpath security/tomoyo/file.c:151 [inline] tomoyo_path_perm+0x230/0x430 security/tomoyo/file.c:822 tomoyo_path_symlink+0xaa/0xf0 security/tomoyo/tomoyo.c:206 security_path_symlink+0x10a/0x170 security/security.c:1010 do_symlinkat+0x137/0x290 fs/namei.c:4150 __do_sys_symlink fs/namei.c:4171 [inline] __se_sys_symlink fs/namei.c:4169 [inline] __x64_sys_symlink+0x59/0x80 fs/namei.c:4169 do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301 entry_SYSCALL_64_after_hwframe+0x49/0xbe Freed by task 11221: save_stack+0x23/0x90 mm/kasan/common.c:71 set_track mm/kasan/common.c:79 [inline] __kasan_slab_free+0x102/0x150 mm/kasan/common.c:451 kasan_slab_free+0xe/0x10 mm/kasan/common.c:459 __cache_free mm/slab.c:3426 [inline] kfree+0x106/0x2a0 mm/slab.c:3753 tomoyo_realpath_from_path+0x1de/0x7a0 security/tomoyo/realpath.c:319 tomoyo_get_realpath security/tomoyo/file.c:151 [inline] tomoyo_path_perm+0x230/0x430 security/tomoyo/file.c:822 tomoyo_path_symlink+0xaa/0xf0 security/tomoyo/tomoyo.c:206 security_path_symlink+0x10a/0x170 security/security.c:1010 do_symlinkat+0x137/0x290 fs/namei.c:4150 __do_sys_symlink fs/namei.c:4171 [inline] __se_sys_symlink fs/namei.c:4169 [inline] __x64_sys_symlink+0x59/0x80 fs/namei.c:4169 do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301 entry_SYSCALL_64_after_hwframe+0x49/0xbe The buggy address belongs to the object at ffff88808a9d2840 which belongs to the cache kmalloc-4k of size 4096 The buggy address is located 1948 bytes inside of 4096-byte region [ffff88808a9d2840, ffff88808a9d3840) The buggy address belongs to the page: page:ffffea00022a7480 refcount:1 mapcount:0 mapping:ffff8880aa400dc0 index:0x0 compound_mapcount: 0 flags: 0x1fffc0000010200(slab|head) raw: 01fffc0000010200 ffffea0002555b08 ffffea0002a44b08 ffff8880aa400dc0 raw: 0000000000000000 ffff88808a9d2840 0000000100000001 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88808a9d2e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88808a9d2f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88808a9d2f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88808a9d3000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88808a9d3080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb 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