Re: memory leak in do_eventfd

[Eric Biggers]

[+Cc kvm mailing list]

On Wed, May 20, 2020 at 06:12:17PM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    5a9ffb95 Merge tag '5.7-rc5-smb3-fixes' of git://git.samba..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=10b72a02100000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=f8295ae5b3f8268d
> dashboard link: https://syzkaller.appspot.com/bug?extid=f196caa45793d6374707
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17585b76100000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12500a02100000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+f196caa45793d6374707@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> BUG: memory leak
> unreferenced object 0xffff888117169ac0 (size 64):
>   comm "syz-executor012", pid 6609, jiffies 4294942172 (age 13.720s)
>   hex dump (first 32 bytes):
>     01 00 00 00 ff ff ff ff 00 00 00 00 00 c9 ff ff  ................
>     d0 9a 16 17 81 88 ff ff d0 9a 16 17 81 88 ff ff  ................
>   backtrace:
>     [<00000000351bb234>] kmalloc include/linux/slab.h:555 [inline]
>     [<00000000351bb234>] do_eventfd+0x35/0xf0 fs/eventfd.c:418
>     [<00000000c2f69a77>] __do_sys_eventfd fs/eventfd.c:443 [inline]
>     [<00000000c2f69a77>] __se_sys_eventfd fs/eventfd.c:441 [inline]
>     [<00000000c2f69a77>] __x64_sys_eventfd+0x14/0x20 fs/eventfd.c:441
>     [<0000000086d6f989>] do_syscall_64+0x6e/0x220 arch/x86/entry/common.c:295
>     [<000000006c5bcb63>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> BUG: memory leak
> unreferenced object 0xffff888117169100 (size 64):
>   comm "syz-executor012", pid 6609, jiffies 4294942172 (age 13.720s)
>   hex dump (first 32 bytes):
>     e8 99 dd 00 00 c9 ff ff e8 99 dd 00 00 c9 ff ff  ................
>     00 00 00 20 00 00 00 00 00 00 00 00 00 00 00 00  ... ............
>   backtrace:
>     [<00000000436d2955>] kmalloc include/linux/slab.h:555 [inline]
>     [<00000000436d2955>] kzalloc include/linux/slab.h:669 [inline]
>     [<00000000436d2955>] kvm_assign_ioeventfd_idx+0x4f/0x270 arch/x86/kvm/../../../virt/kvm/eventfd.c:798
>     [<00000000e89390cc>] kvm_assign_ioeventfd arch/x86/kvm/../../../virt/kvm/eventfd.c:934 [inline]
>     [<00000000e89390cc>] kvm_ioeventfd+0xbb/0x194 arch/x86/kvm/../../../virt/kvm/eventfd.c:961
>     [<00000000ba9f6732>] kvm_vm_ioctl+0x1e6/0x1030 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3670
>     [<000000005da94937>] vfs_ioctl fs/ioctl.c:47 [inline]
>     [<000000005da94937>] ksys_ioctl+0xa6/0xd0 fs/ioctl.c:771
>     [<00000000a583d097>] __do_sys_ioctl fs/ioctl.c:780 [inline]
>     [<00000000a583d097>] __se_sys_ioctl fs/ioctl.c:778 [inline]
>     [<00000000a583d097>] __x64_sys_ioctl+0x1a/0x20 fs/ioctl.c:778
>     [<0000000086d6f989>] do_syscall_64+0x6e/0x220 arch/x86/entry/common.c:295
>     [<000000006c5bcb63>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> 
> 
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx
> 
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> 
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