From e2938ad00b21340c0362562dfedd7cfec0554d67 Mon Sep 17 00:00:00 2001 From: System Administrator Date: Thu, 9 Oct 2025 16:35:00 +0000 Subject: [PATCH] apparmor: fix NULL pointer dereference in __unix_needs_revalidation MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit When receiving file descriptors via SCM_RIGHTS, both the socket pointer and the socket's sk pointer can be NULL during socket setup or teardown, causing NULL pointer dereferences in __unix_needs_revalidation(). This is a regression in AppArmor 5.0.0 (kernel 6.17+) where the new __unix_needs_revalidation() function was added without proper NULL checks. The crash manifests as: BUG: kernel NULL pointer dereference, address: 0x0000000000000018 RIP: aa_file_perm+0xb7/0x3b0 (or +0xbe/0x3b0, +0xc0/0x3e0) Call Trace: apparmor_file_receive+0x42/0x80 security_file_receive+0x2e/0x50 receive_fd+0x1d/0xf0 scm_detach_fds+0xad/0x1c0 The function dereferences sock->sk->sk_family without checking if either sock or sock->sk is NULL first. Add NULL checks for both sock and sock->sk before accessing sk_family. Fixes: 88fec3526e841 ("apparmor: make sure unix socket labeling is correctly updated.") Reported-by: Jamin Mc Closes: https://bugzilla.proxmox.com/show_bug.cgi?id=7083 Closes: https://gitlab.com/apparmor/apparmor/-/issues/568 Signed-off-by: Fabian Grünbichler Signed-off-by: System Administrator Signed-off-by: John Johansen --- security/apparmor/file.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/security/apparmor/file.c b/security/apparmor/file.c index c758204028780..919dbbbc87ab6 100644 --- a/security/apparmor/file.c +++ b/security/apparmor/file.c @@ -578,6 +578,9 @@ static bool __unix_needs_revalidation(struct file *file, struct aa_label *label, return false; if (request & NET_PEER_MASK) return false; + /* sock and sock->sk can be NULL for sockets being set up or torn down */ + if (!sock || !sock->sk) + return false; if (sock->sk->sk_family == PF_UNIX) { struct aa_sk_ctx *ctx = aa_sock(sock->sk); -- 2.47.3