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    SubjectRe: net/kcm: double free of kcm inode
    On Thu, Mar 23, 2017 at 5:09 AM, Dmitry Vyukov <dvyukov@google.com> wrote:
    > Hello,
    >
    > I've got the following report while running syzkaller fuzzer. Note the
    > preceding kmem_cache_alloc injected failure, it's most likely the root
    > cause.
    >
    > FAULT_INJECTION: forcing a failure.
    > name failslab, interval 1, probability 0, space 0, times 0
    > CPU: 1 PID: 21839 Comm: syz-executor4 Not tainted 4.11.0-rc3+ #364
    > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
    > Call Trace:
    > __dump_stack lib/dump_stack.c:16 [inline]
    > dump_stack+0x1b8/0x28d lib/dump_stack.c:52
    > fail_dump lib/fault-inject.c:45 [inline]
    > should_fail+0x78a/0x870 lib/fault-inject.c:154
    > should_failslab+0xec/0x120 mm/failslab.c:31
    > slab_pre_alloc_hook mm/slab.h:434 [inline]
    > slab_alloc mm/slab.c:3394 [inline]
    > kmem_cache_alloc+0x200/0x720 mm/slab.c:3570
    > sk_prot_alloc+0x65/0x2a0 net/core/sock.c:1331
    > sk_alloc+0x8c/0x710 net/core/sock.c:1393
    > kcm_clone net/kcm/kcmsock.c:1655 [inline]
    > kcm_ioctl+0xb65/0x17e0 net/kcm/kcmsock.c:1713
    > sock_do_ioctl+0x65/0xb0 net/socket.c:895
    > sock_ioctl+0x2c2/0x440 net/socket.c:993
    > vfs_ioctl fs/ioctl.c:45 [inline]
    > do_vfs_ioctl+0x1af/0x16d0 fs/ioctl.c:685
    > SYSC_ioctl fs/ioctl.c:700 [inline]
    > SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
    > entry_SYSCALL_64_fastpath+0x1f/0xc2

    I don't know if this patch could fix this bug or not:
    https://patchwork.ozlabs.org/patch/742860/

    This is why I don't add your Reported-by. But it could be related.

    Thanks.

    > RIP: 0033:0x445b79
    > RSP: 002b:00007f05eb28e858 EFLAGS: 00000286 ORIG_RAX: 0000000000000010
    > RAX: ffffffffffffffda RBX: 0000000000708000 RCX: 0000000000445b79
    > RDX: 0000000020001000 RSI: 00000000000089e2 RDI: 0000000000000005
    > RBP: 0000000000000086 R08: 0000000000000000 R09: 0000000000000000
    > R10: 0000000000000000 R11: 0000000000000286 R12: 00000000004a7e31
    > R13: 0000000000000000 R14: 00007f05eb28e618 R15: 00007f05eb28e788
    > ==================================================================
    > BUG: KASAN: use-after-free in __fput+0x6b0/0x7f0 fs/file_table.c:211
    > at addr ffff880037a25670
    > Read of size 2 by task syz-executor4/21839
    > CPU: 1 PID: 21839 Comm: syz-executor4 Not tainted 4.11.0-rc3+ #364
    > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
    > Call Trace:
    > __dump_stack lib/dump_stack.c:16 [inline]
    > dump_stack+0x1b8/0x28d lib/dump_stack.c:52
    > kasan_object_err+0x1c/0x70 mm/kasan/report.c:166
    > print_address_description mm/kasan/report.c:210 [inline]
    > kasan_report_error mm/kasan/report.c:294 [inline]
    > kasan_report.part.2+0x1be/0x480 mm/kasan/report.c:316
    > kasan_report mm/kasan/report.c:335 [inline]
    > __asan_report_load2_noabort+0x29/0x30 mm/kasan/report.c:335
    > __fput+0x6b0/0x7f0 fs/file_table.c:211
    > ____fput+0x15/0x20 fs/file_table.c:245
    > task_work_run+0x1a4/0x270 kernel/task_work.c:116
    > tracehook_notify_resume include/linux/tracehook.h:191 [inline]
    > exit_to_usermode_loop+0x24d/0x2d0 arch/x86/entry/common.c:161
    > prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline]
    > syscall_return_slowpath+0x3bd/0x460 arch/x86/entry/common.c:260
    > entry_SYSCALL_64_fastpath+0xc0/0xc2
    > RIP: 0033:0x445b79
    > RSP: 002b:00007f05eb28e858 EFLAGS: 00000286 ORIG_RAX: 0000000000000010
    > RAX: fffffffffffffff4 RBX: 0000000000708000 RCX: 0000000000445b79
    > RDX: 0000000020001000 RSI: 00000000000089e2 RDI: 0000000000000005
    > RBP: 0000000000002170 R08: 0000000000000000 R09: 0000000000000000
    > R10: 0000000000000000 R11: 0000000000000286 R12: 00000000006e0230
    > R13: 00000000000089e2 R14: 0000000020001000 R15: 0000000000000005
    > Object at ffff880037a25640, in cache sock_inode_cache size: 944
    > Allocated:
    > PID = 21839
    > save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
    > save_stack+0x43/0xd0 mm/kasan/kasan.c:517
    > set_track mm/kasan/kasan.c:529 [inline]
    > kasan_kmalloc+0xbc/0xf0 mm/kasan/kasan.c:620
    > kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:559
    > kmem_cache_alloc+0x110/0x720 mm/slab.c:3572
    > sock_alloc_inode+0x70/0x300 net/socket.c:250
    > alloc_inode+0x65/0x180 fs/inode.c:207
    > new_inode_pseudo+0x69/0x190 fs/inode.c:889
    > sock_alloc+0x41/0x270 net/socket.c:565
    > kcm_clone net/kcm/kcmsock.c:1634 [inline]
    > kcm_ioctl+0x990/0x17e0 net/kcm/kcmsock.c:1713
    > sock_do_ioctl+0x65/0xb0 net/socket.c:895
    > sock_ioctl+0x2c2/0x440 net/socket.c:993
    > vfs_ioctl fs/ioctl.c:45 [inline]
    > do_vfs_ioctl+0x1af/0x16d0 fs/ioctl.c:685
    > SYSC_ioctl fs/ioctl.c:700 [inline]
    > SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
    > entry_SYSCALL_64_fastpath+0x1f/0xc2
    > Freed:
    > PID = 21839
    > save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
    > save_stack+0x43/0xd0 mm/kasan/kasan.c:517
    > set_track mm/kasan/kasan.c:529 [inline]
    > kasan_slab_free+0x81/0xc0 mm/kasan/kasan.c:593
    > __cache_free mm/slab.c:3514 [inline]
    > kmem_cache_free+0x71/0x240 mm/slab.c:3774
    > sock_destroy_inode+0x56/0x70 net/socket.c:280
    > destroy_inode+0x15d/0x200 fs/inode.c:264
    > evict+0x57e/0x920 fs/inode.c:570
    > iput_final fs/inode.c:1515 [inline]
    > iput+0x62b/0xa20 fs/inode.c:1542
    > sock_release+0x168/0x1e0 net/socket.c:607
    > sock_close+0x16/0x20 net/socket.c:1061
    > __fput+0x327/0x7f0 fs/file_table.c:209
    > ____fput+0x15/0x20 fs/file_table.c:245
    > task_work_run+0x1a4/0x270 kernel/task_work.c:116
    > tracehook_notify_resume include/linux/tracehook.h:191 [inline]
    > exit_to_usermode_loop+0x24d/0x2d0 arch/x86/entry/common.c:161
    > prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline]
    > syscall_return_slowpath+0x3bd/0x460 arch/x86/entry/common.c:260
    > entry_SYSCALL_64_fastpath+0xc0/0xc2
    > Memory state around the buggy address:
    > ffff880037a25500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    > ffff880037a25580: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
    >>ffff880037a25600: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
    > ^
    > ffff880037a25680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    > ffff880037a25700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    > ==================================================================
    >
    > On commit 093b995e3b55a0ae0670226ddfcb05bfbf0099ae

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