Linux Kernel SMB Client iface_list Race During Concurrent Interface Refresh Creates a Network-Triggered Use-After-Free

Status: UPDATED  |  Advisory ID: CVE-2026-98173

Key Details

Affected Products, Subsystems & Sectors

What to Know

In the Linux kernel, the following vulnerability has been resolved:

smb: client: fix use-after-free of iface in cifs_try_adding_channels()

cifs_try_adding_channels() iterates ses->iface_list with

list_for_each_entry_safe_from(), which captures the next entry

(niface) under iface_lock. The loop body then drops iface_lock for

the whole duration of cifs_ses_add_channel().

A concurrent interface refresh (SMB3_request_interfaces() ->

parse_server_interfaces()) marks all ifaces inactive and removes and

frees any that are not re-advertised via list_del() + kref_put(),

where release_iface() is a bare kfree(). Since niface typically has

no channel holding a reference, the list reference is its last and it

can be freed inside the unlocked window. On continue, the iterator

advance step then dereferences niface->iface_head.next, and the loop

body reads iface->rdma_capable/is_active, both on freed memory.

Fix this by never keeping an unreferenced list pointer across the

unlocked window. Each channel attempt now re-scans the list from the

head under iface_lock, takes a kref on the selected candidate, and

passes only that referenced candidate to cifs_ses_add_channel().

weight_fulfilled still tracks selection progress, so restarting the

scan preserves the original weighted distribution and the

weight_fulfilled-before-kref_put ordering on the failure path.

Add a per-pass attempts cap so a flapping interface refresh cannot

keep the inner loop spinning within a single tries increment. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References