This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed- focal' to 'verification-done-focal'. If the problem still exists, change the tag 'verification-needed-focal' to 'verification-failed-focal'.
If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you! ** Tags added: verification-needed-focal -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1883962 Title: apparmor reference leak causes refcount_t overflow with af_alg_accept() Status in linux package in Ubuntu: Fix Committed Status in linux source package in Bionic: Fix Committed Status in linux source package in Eoan: Fix Released Status in linux source package in Focal: Fix Committed Status in linux source package in Groovy: Invalid Bug description: [Impact] * Users of the Crypto (user-space) API (i.e., AF_ALG) can trigger refcount errors in AppArmor under high load (might lead to memory leak or use after free.) * There is a reference leak in AppArmor when af_alg_accept() calls security_sock_graft() and then security_sk_clone(). * Both acquire a reference to a label, to assign it to the same pointer, but the latter does not release the former's acquired reference (before overwriting the pointer value.) * This reference leak builds up over time, and under high load can eventually overflow/underflow/saturate refcount, depending on which value it has when a program hits that. * The fix just checks if the pointer has an assigned label, then releases its acquired reference. [Test Case] * See comment #1 for the test-case 'aa-refcnt-af_alg.c'. * Exercise that code path indefinitely until it hits the refcount_t overflow/underflow/saturate message (or not, with the patch.) (see comment #4) * It's possible to monitor refcount values with kprobes, to confirm whether or not the problem is happening. (see comments #2 and #3) [Other Info] * Patch applied upstream on v5.8-rc1 [1] * Applied on Unstable (tag Ubuntu-5.8-5.8.0-0.1) * Not required on Groovy (still 5.4; should sync from Unstable) * Not required on Eoan (EOL date before SRU cycle release date) * Required on Bionic and Focal. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=3b646abc5bc6c0df649daea4c2c976bd4d47e4c8 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1883962/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
