In the Linux kernel, the following vulnerability has been resolved:
nvme-fc: fix double free of fabrics options when nvme_add_ctrl() fails
nvmf_create_ctrl() owns the fabrics options and frees them whenever
->create_ctrl() returns an error, so a transport must not free them on
its own error paths. nvme-fc tracks this by testing ctrl->ctrl.opts in
nvme_fc_ctrl_free(), which requires nvme_fc_init_ctrl() to clear that
pointer on every error exit.
The coupling is implicit, and commit 1a9e218195a5 ("nvme: split device
add from initialization") broke it by adding a second error exit. When
nvme_add_ctrl() fails, nvme_fc_init_ctrl() jumps to out_put_ctrl:, past
the "ctrl->ctrl.opts = NULL" that only sits on the fail_ctrl: path, so
nvme_fc_ctrl_free() frees the options and nvmf_create_ctrl() frees them
a second time:
BUG: KASAN: slab-use-after-free in nvmf_free_options+0x30/0x190
nvmf_free_options+0x30/0x190 drivers/nvme/host/fabrics.c:1284
nvmf_create_ctrl drivers/nvme/host/fabrics.c:1374 [inline]
Freed by task 5534:
nvme_fc_ctrl_free drivers/nvme/host/fc.c:2374 [inline]
nvme_fc_init_ctrl+0xe17/0x1450 drivers/nvme/host/fc.c:3605
nvme_add_ctrl() fails when dev_set_name() cannot allocate, so this is
reachable under memory pressure or fault injection. Without KASAN the
options are freed twice.
Rather than clear the pointer on the second exit as well, derive
ownership the way nvme-tcp, nvme-rdma and nvme-loop do, from list
membership: their free_ctrl leaves the options alone unless the
controller made it onto the transport list.
The list cannot simply be populated on the success path as it is there.
nvme-fc runs the initial connect synchronously via flush_delayed_work(),
and the controller has to be reachable on rport->ctrl_list for the whole
of it: nvme_fc_unregister_remoteport() needs to find it to signal
connectivity loss, nvme_fc_match_disconn_ls() matches an incoming
Disconnect Association LS against ctrl->association_id, which is only
assigned during that window, nvme_fc_resume_controller() needs it on
remoteport re-registration, and nvme_fc_existing_controller() uses it to
reject a duplicate connect racing the one in flight.
Keep the insertion where it is and add a fail_unlist: label, falling
into fail_ctrl:, for the error paths that run after it. The earlier
error paths never reach the insertion and keep using fail_ctrl:
directly, so the list is only touched where the controller is actually
on it.
nvme_fc_ctrl_free() cannot use the plain "goto free_ctrl" the other
transports use, because it still has to put_device(), release the rport
reference and free the ida entry for resources taken before the
insertion. Sample list_empty() under rport->lock instead.
ctrl->ctrl.opts also stays valid for the whole teardown now. That is
not the bug being fixed, but it removes some fragility around the old
idiom: nvme_free_ctrl() calls nvme_auth_free() before ->free_ctrl(), and
ctrl_max_dhchaps() dereferences ctrl->opts without a NULL check when
ctrl->dhchap_ctxs is set, which nvme-fc permits since NVMF_ALLOWED_OPTS
allows the dhchap options. The nvme sysfs attributes that dereference
ctrl->opts, such as hostnqn and address, evaluate their is_visible()
test once at device_add() time and stay readable until
cdev_device_del().
CVSS Vector: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS Score: 7.5
AV:A - A rogue NVMe-FC target on the Fibre Channel SAN causes nvme-cli udev autoconnect (FC_EVENT=nvmediscovery runs nvmf-connect, which writes /dev/nvme-fabrics and reaches nvme_fc_init_ctrl). FC/FCoE is a non-routable storage fabric, so this is Adjacent, matching prior nvme-fc scores.
AC:H - The double-free runs only when nvme_add_ctrl() fails in dev_set_name() or cdev_device_add(), which the fix notes is reached under memory pressure or failslab. A fabric peer can provoke the connect but cannot reliably force that GFP_KERNEL/sysfs allocation to fail.
PR:N - The attacker is an unauthenticated NVMe-FC peer; udev/systemd nvmf-autoconnect writes /dev/nvme-fabrics as root, and NVMe-FC does not authenticate the remote port, so no host account or capability is required.
UI:N - nvmf-autoconnect and nvmefc-boot-connections invoke nvme connect automatically on FC discovery and boot, so no administrator or interactive user action is required at exploit time.
S:U - The double-free corrupts the kernel slab allocator and nvmf_ctrl_options inside the host kernel's own security authority; no VM, IOMMU, or sandbox boundary is crossed.
C:H - After nvme_fc_ctrl_free() kfree's opts, nvmf_create_ctrl() calls nvmf_free_options() which reads opts->host, keyring, tls_key, and the option string pointers from freed, sprayable heap, giving an arbitrary kernel read primitive.
I:H - The second nvmf_free_options() kfree's those reclaimed pointers and the opts object itself (slab double-free of nvmf_ctrl_options), enabling allocator metadata corruption, an arbitrary-free primitive, and control-flow hijack via heap grooming.
A:H - KASAN reports slab-use-after-free in nvmf_free_options(); without KASAN the double-free of opts and its member strings oopses or panics the kernel.
| Attack Vector |
Adjacent Network |
Scope |
Unchanged |
| Attack Complexity |
High |
Confidentiality Impact |
High |
| Privileges Required |
None |
Integrity Impact |
High |
| User Interaction |
None |
Availability Impact |
High |
AV:A - A rogue NVMe-FC target on the Fibre Channel SAN causes nvme-cli udev autoconnect (FC_EVENT=nvmediscovery runs nvmf-connect, which writes /dev/nvme-fabrics and reaches nvme_fc_init_ctrl). FC/FCoE is a non-routable storage fabric, so this is Adjacent, matching prior nvme-fc scores.
AC:H - The double-free runs only when nvme_add_ctrl() fails in dev_set_name() or cdev_device_add(), which the fix notes is reached under memory pressure or failslab. A fabric peer can provoke the connect but cannot reliably force that GFP_KERNEL/sysfs allocation to fail.
PR:N - The attacker is an unauthenticated NVMe-FC peer; udev/systemd nvmf-autoconnect writes /dev/nvme-fabrics as root, and NVMe-FC does not authenticate the remote port, so no host account or capability is required.
UI:N - nvmf-autoconnect and nvmefc-boot-connections invoke nvme connect automatically on FC discovery and boot, so no administrator or interactive user action is required at exploit time.
S:U - The double-free corrupts the kernel slab allocator and nvmf_ctrl_options inside the host kernel's own security authority; no VM, IOMMU, or sandbox boundary is crossed.
C:H - After nvme_fc_ctrl_free() kfree's opts, nvmf_create_ctrl() calls nvmf_free_options() which reads opts->host, keyring, tls_key, and the option string pointers from freed, sprayable heap, giving an arbitrary kernel read primitive.
I:H - The second nvmf_free_options() kfree's those reclaimed pointers and the opts object itself (slab double-free of nvmf_ctrl_options), enabling allocator metadata corruption, an arbitrary-free primitive, and control-flow hijack via heap grooming.
A:H - KASAN reports slab-use-after-free in nvmf_free_options(); without KASAN the double-free of opts and its member strings oopses or panics the kernel.
CVSS 3.1