[{"id":3674618,"web_url":"http://patchwork.ozlabs.org/comment/3674618/","msgid":"<2a69475a-5fed-463e-bad1-0747c2daf623@canonical.com>","list_archive_url":null,"date":"2026-04-08T07:32:49","subject":"ACK: [SRU][Q][PATCH 0/1] apparmor: fix NULL pointer dereference in\n __unix_needs_revalidation","submitter":{"id":92836,"url":"http://patchwork.ozlabs.org/api/people/92836/","name":"Yufeng Gao","email":"yufeng.gao@canonical.com"},"content":"On 8/4/26 03:30, Georgia Garcia wrote:\n> BugLink: http://bugs.launchpad.net/bugs/2147374\n>\n> SRU Justification:\n>\n> [Impact]\n>\n> When receiving file descriptors via SCM_RIGHTS, both the socket pointer\n> and the socket's sk pointer can be NULL during socket setup or teardown,\n> causing NULL pointer dereferences in __unix_needs_revalidation().\n>\n> This 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>\n> Cherry-pick uptream linux commit:\n> e2938ad00b21340c0362562dfedd7cfec0554d67\n>\n> [Test Plan]\n>\n> Run the following POC and check that creating the nested-vm doesn't\n> cause a NULL pointer dereference in dmesg\n>\n> cat << EOF > poc.sh\n> #!/bin/bash\n> set -eux\n>\n> # VM inside container causes a kernel NULL pointer dereference on 6.17\n> if [[ \"$(uname -r)\" =~ ^6\\.17\\.0 ]]; then\n> echo \"::warning:: 6.17 kernel detected, expect failure then check 'dmesg'\"\n> else\n> echo \"::info:: 6.17 kernel NOT detected, expect success and consider switching to 'linux-image-generic-hwe-24.04'\"\n> fi\n>\n> snap install lxd --channel latest/edge\n> lxd init --auto\n>\n> # prepare ctn to be used for nested VM testing\n> lxc init ubuntu-minimal-daily:24.04 ctn -c security.devlxd.images=true -c security.nesting=true -s default\n> lxc config device add ctn kvm unix-char source=/dev/kvm\n> lxc config device add ctn vhost-net unix-char source=/dev/vhost-net\n> lxc config device add ctn vhost-vsock unix-char source=/dev/vhost-vsock\n> lxc config device add ctn vsock unix-char source=/dev/vsock\n>\n> lxc start ctn\n> sleep 30\n> lxc exec ctn -- snap wait system seed.loaded\n>\n> lxc exec ctn -- snap install lxd --channel latest/edge\n> lxc exec ctn -- lxd init --auto\n>\n> # launch small nested VM\n> lxc exec ctn -- lxc launch ubuntu-minimal-daily:24.04 nested-vm --vm -c limits.memory=512MiB -d root,size=3584MiB\n>\n> # cleanup\n> lxc delete -f ctn\n> EOF\n>\n> [Where problems could occur]\n>\n> The regression can be considered as low since both fixes have been\n> applied to the upstream kernel.\n>\n> System 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(+)\n>\nAcked-by: Yufeng Gao ","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=fail reason=\"signature verification failed\" (4096-bit key;\n unprotected) header.d=canonical.com header.i=@canonical.com\n header.a=rsa-sha256 header.s=20251003 header.b=MdtanCZ+;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ubuntu.com\n (client-ip=185.125.189.65; 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