From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-64140: ksmbd: fix null pointer dereference in proc_show_files()
Date: Sun, 19 Jul 2026 17:40:02 +0200 [thread overview]
Message-ID: <2026071929-CVE-2026-64140-c119@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix null pointer dereference in proc_show_files()
When a SMB2 client opens a file with a durable v2 handle and then issues
SMB2 SESSION_LOGOFF, session_fd_check() clears fp->tcon = NULL on the
reconnectable file pointer but leaves the fp registered in global_ft.idr
until the durable scavenger fires (up to fp->durable_timeout seconds
later).
During that window any read of /proc/fs/ksmbd/files (mode 0400) panics
the kernel because proc_show_files() walks global_ft.idr and
unconditionally dereferences fp->tcon->id with no NULL guard.
Reproducer requires only a successful SMB2 SESSION_SETUP and a share
configured with 'durable handles = yes'. KASAN report on mainline
70390501d194:
general protection fault, probably for non-canonical address
0xdffffc0000000000: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
RIP: 0010:proc_show_files+0x118/0x740
Call Trace:
proc_show_files+0x118/0x740
seq_read_iter+0x4ef/0xe10
proc_reg_read_iter+0x1b7/0x280
...
Guard the dereference. A durable-disconnected fp legitimately has no
tcon; report its tree id as 0 rather than oopsing.
The Linux kernel CVE team has assigned CVE-2026-64140 to this issue.
Affected and fixed versions
===========================
Issue introduced in 7.0 with commit b38f99c1217ae04753340f0fdcd8f35bf56841dc and fixed in 7.0.11 with commit 8eab081627b67216d1c8f638b68289b500dc9a6b
Issue introduced in 7.0 with commit b38f99c1217ae04753340f0fdcd8f35bf56841dc and fixed in 7.1 with commit 904901561e61a2b559070b20c74a8c95491f30aa
Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.
Unaffected versions might change over time as fixes are backported to
older supported kernel versions. The official CVE entry at
https://cve.org/CVERecord/?id=CVE-2026-64140
will be updated if fixes are backported, please check that for the most
up to date information about this issue.
Affected files
==============
The file(s) affected by this issue are:
fs/smb/server/vfs_cache.c
Mitigation
==========
The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes. Individual
changes are never tested alone, but rather are part of a larger kernel
release. Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all. If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
https://git.kernel.org/stable/c/8eab081627b67216d1c8f638b68289b500dc9a6b
https://git.kernel.org/stable/c/904901561e61a2b559070b20c74a8c95491f30aa
reply other threads:[~2026-07-19 15:45 UTC|newest]
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