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charset=\"utf-8\"","Content-Transfer-Encoding":"base64","Errors-To":"kernel-team-bounces@lists.ubuntu.com","Sender":"\"kernel-team\" "},"content":"BugLink: http://bugs.launchpad.net/bugs/2147374\n\nSRU Justification:\n\n[Impact]\n\nWhen receiving file descriptors via SCM_RIGHTS, both the socket pointer\nand the socket's sk pointer can be NULL during socket setup or teardown,\ncausing NULL pointer dereferences in __unix_needs_revalidation().\n\nThis is a regression in AppArmor 5.0.0 (kernel 6.17+) where the new\n__unix_needs_revalidation() function was added without proper NULL checks.\n\n[ 287.713912] BUG: kernel NULL pointer dereference, address: 0000000000000018\n[ 287.714922] #PF: supervisor read access in kernel mode\n[ 287.715653] #PF: error_code(0x0000) - not-present page\n[ 287.716378] PGD 0 P4D 0 \n[ 287.716749] Oops: Oops: 0000 [#1] SMP NOPTI\n[ 287.717347] CPU: 0 UID: 1000000 PID: 7587 Comm: aa-exec Tainted: G E 6.17.13+ #19 PREEMPT(voluntary) \n[ 287.718806] Tainted: [E]=UNSIGNED_MODULE\n[ 287.719370] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014\n[ 287.720729] RIP: 0010:aa_file_perm+0xb9/0x3b0\n\n[Fix]\n\nCherry-pick uptream linux commit:\ne2938ad00b21340c0362562dfedd7cfec0554d67\n\n[Test Plan]\n\nRun the following POC and check that creating the nested-vm doesn't\ncause a NULL pointer dereference in dmesg\n\ncat << EOF > poc.sh\n#!/bin/bash\nset -eux\n\n# VM inside container causes a kernel NULL pointer dereference on 6.17\nif [[ \"$(uname -r)\" =~ ^6\\.17\\.0 ]]; then\n echo \"::warning:: 6.17 kernel detected, expect failure then check 'dmesg'\"\nelse\n echo \"::info:: 6.17 kernel NOT detected, expect success and consider switching to 'linux-image-generic-hwe-24.04'\"\nfi\n\nsnap install lxd --channel latest/edge\nlxd init --auto\n\n# prepare ctn to be used for nested VM testing\nlxc init ubuntu-minimal-daily:24.04 ctn -c security.devlxd.images=true -c security.nesting=true -s default\nlxc config device add ctn kvm unix-char source=/dev/kvm\nlxc config device add ctn vhost-net unix-char source=/dev/vhost-net\nlxc config device add ctn vhost-vsock unix-char source=/dev/vhost-vsock\nlxc config device add ctn vsock unix-char source=/dev/vsock\n\nlxc start ctn\nsleep 30\nlxc exec ctn -- snap wait system seed.loaded\n\nlxc exec ctn -- snap install lxd --channel latest/edge\nlxc exec ctn -- lxd init --auto\n\n# launch small nested VM\nlxc exec ctn -- lxc launch ubuntu-minimal-daily:24.04 nested-vm --vm -c limits.memory=512MiB -d root,size=3584MiB\n\n# cleanup\nlxc delete -f ctn\nEOF\n\n[Where problems could occur]\n\nThe regression can be considered as low since both fixes have been\napplied to the upstream kernel.\n\nSystem Administrator (1):\n apparmor: fix NULL pointer dereference in __unix_needs_revalidation\n\n security/apparmor/file.c | 3 +++\n 1 file changed, 3 insertions(+)"}