Monitoring the label reference count with the kprobes module: - original kernel: the counter keeps increasing on every pair of accept()/release() syscalls. - modified kernel: the counter keeps stable.
Focal: ----- original) $ uname -rv 5.4.0-38-generic #42-Ubuntu SMP Mon Jun 8 14:14:24 UTC 2020 $ ./aa-refcnt-af_alg & $ sudo insmod kmod.ko ... [ 4739.811403] accept() :: comm = aa-refcnt-af_al, pid = 1023, sk->sk_security->label->count = 0x40b395e0 [ 4739.813677] release() :: comm = aa-refcnt-af_al, pid = 1023, sk->sk_security->label->count = 0x40b395e2 [ 4739.815994] accept() :: comm = aa-refcnt-af_al, pid = 1023, sk->sk_security->label->count = 0x40b395e1 [ 4739.818274] release() :: comm = aa-refcnt-af_al, pid = 1023, sk->sk_security->label->count = 0x40b395e3 [ 4739.820555] accept() :: comm = aa-refcnt-af_al, pid = 1023, sk->sk_security->label->count = 0x40b395e2 [ 4739.822833] release() :: comm = aa-refcnt-af_al, pid = 1023, sk->sk_security->label->count = 0x40b395e4 ... $ sudo rmmod kmod modified) $ uname -rv 5.4.0-38-generic #42+test20200617b1 SMP Wed Jun 17 16:31:24 -03 2020 $ ./aa-refcnt-af_alg & $ sudo insmod kmod.ko ... [ 185.657133] accept() :: comm = aa-refcnt-af_al, pid = 1098, sk->sk_security->label->count = 0x649 [ 185.660720] release() :: comm = aa-refcnt-af_al, pid = 1098, sk->sk_security->label->count = 0x64a [ 185.664321] accept() :: comm = aa-refcnt-af_al, pid = 1098, sk->sk_security->label->count = 0x649 [ 185.668981] release() :: comm = aa-refcnt-af_al, pid = 1098, sk->sk_security->label->count = 0x64a [ 185.672648] accept() :: comm = aa-refcnt-af_al, pid = 1098, sk->sk_security->label->count = 0x629 [ 185.676299] release() :: comm = aa-refcnt-af_al, pid = 1098, sk->sk_security->label->count = 0x62a ... $ sudo rmmod kmod Bionic: ------ original) $ uname -rv 4.15.0-107-generic #108-Ubuntu SMP Mon Jun 8 17:51:33 UTC 2020 $ ./aa-refcnt-af_alg & $ sudo insmod kmod.ko ... [ 4333.136581] accept() :: comm = aa-refcnt-af_al, pid = 1243, sk->sk_security->label->count = 0x449b9e85 [ 4333.139131] release() :: comm = aa-refcnt-af_al, pid = 1243, sk->sk_security->label->count = 0x449b9e87 [ 4333.141650] accept() :: comm = aa-refcnt-af_al, pid = 1243, sk->sk_security->label->count = 0x449b9e86 [ 4333.144142] release() :: comm = aa-refcnt-af_al, pid = 1243, sk->sk_security->label->count = 0x449b9e88 [ 4333.146675] accept() :: comm = aa-refcnt-af_al, pid = 1243, sk->sk_security->label->count = 0x449b9e87 [ 4333.149199] release() :: comm = aa-refcnt-af_al, pid = 1243, sk->sk_security->label->count = 0x449b9e89 ... $ sudo rmmod kmod modified) $ uname -rv 4.15.0-107-generic #108+test20200617b1 SMP Wed Jun 17 16:33:16 -03 2020 $ ./aa-refcnt-af_alg & $ sudo insmod kmod.ko ... [ 245.921217] accept() :: comm = aa-refcnt-af_al, pid = 1165, sk->sk_security->label->count = 0x608 [ 245.923456] release() :: comm = aa-refcnt-af_al, pid = 1165, sk->sk_security->label->count = 0x609 [ 245.925718] accept() :: comm = aa-refcnt-af_al, pid = 1165, sk->sk_security->label->count = 0x608 [ 245.927954] release() :: comm = aa-refcnt-af_al, pid = 1165, sk->sk_security->label->count = 0x609 [ 245.930221] accept() :: comm = aa-refcnt-af_al, pid = 1165, sk->sk_security->label->count = 0x608 [ 245.932469] release() :: comm = aa-refcnt-af_al, pid = 1165, sk->sk_security->label->count = 0x609 ... $ sudo rmmod kmod -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1883962 Title: apparmor reference leak causes refcount_t overflow with af_alg_accept() To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1883962/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
