From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6E09F46D57B; Tue, 21 Jul 2026 18:20:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784658041; cv=none; b=JQ4WL/LxjM3GgN9wr04nMQ8wDPxiNFDpNNRs11FwoK1uP02elxbSThe//F/C7b/C6C4PIsh7y9KyMXlwOOAJOit6zUG+xpRUk1DjH2BlSfxWXkuj6Bw8NKHKV+LtjZw3rp+7XpI3KCWBNm4eCEH0lsb5W6sgxBzy+bCck5J58Zo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784658041; c=relaxed/simple; bh=m+7Lo3N6WwujkDCJXBpjKRE2BJh6SqpKCT8vIa1MQMg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=CyZXfaERP268Zt1KGCa1FazuZ+FVM+dmhR4kGcSRmbC+cDjeKMObm8bWERMbk0URCRC8nWxD5/Rg3px0sYjwB/OHCsDLd6UKZrPPuyvnvvMasoE/eQOEBB6VOe1dC4A3IYNmqsDezD29U1z+gfv671DnancbSYvPJbWkUJeyNKA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=OTZAwHfA; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="OTZAwHfA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 93D7F1F00A3D; Tue, 21 Jul 2026 18:20:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784658040; bh=xzE0UQBbRIDbvQXUzBuxoNRv6rGu/zyCwPuW+iNBaF0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=OTZAwHfAtOQrDACrgK+ivOm3/pUWHuQkUYKj15CBq7EaoudoeuU2cx9fe2goE7IiW tdonObWDiTrZMOFdUrusX2Ql2DaWDj4oxkxm3GHLQ7Vf6kJy7V239edFn0I0/P4DDD ywbZFxSCiZj9L/shtvv6A8UwTbj4o1PW9XcEjmG4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Gil Portnoy , Namjae Jeon , Steve French , Sasha Levin Subject: [PATCH 6.18 0993/1611] ksmbd: fix use-after-free of fp->owner.name in durable handle owner check Date: Tue, 21 Jul 2026 17:18:29 +0200 Message-ID: <20260721152537.728209851@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152514.750365251@linuxfoundation.org> References: <20260721152514.750365251@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gil Portnoy [ Upstream commit 38637163501fd9e2f684b8cd275d0db5d79f37c6 ] Two concurrent SMB2 durable reconnects (DH2C/DHnC) on the same persistent_id race the fp->owner.name compare-read in ksmbd_vfs_compare_durable_owner() against the kfree() in ksmbd_reopen_durable_fd()'s reopen-success path. fp->owner.name is a standalone kstrdup() buffer whose lifetime is independent of the fp refcount, and the two sites share no lock: the compare reads the buffer while the reopen frees it, so the strcmp() can dereference freed memory. Commit 7ce4fc40018d ("ksmbd: fix durable reconnect double-bind race in ksmbd_reopen_durable_fd") made the fp->conn claim atomic under global_ft.lock (closing the owner.name double-free and the ksmbd_file write-UAF), but the compare-read versus reopen-free pair was left unserialized. BUG: KASAN: slab-use-after-free in strcmp+0x2c/0x80 Read of size 1 by task kworker strcmp ksmbd_vfs_compare_durable_owner smb2_check_durable_oplock smb2_open Freed by task kworker: kfree ksmbd_reopen_durable_fd smb2_open Allocated by task kworker: kstrdup session_fd_check smb2_session_logoff The buggy address belongs to the cache kmalloc-8 Serialize both sides of the race with fp->f_lock. The global durable file-table lock still protects the durable reconnect claim, but fp->owner.name is per-open state and does not need to block unrelated durable table lookups or reconnects. The teardown is left at its existing location after the reopen-success point so that an __open_id() rollback still retains owner.name for a later legitimate reconnect to verify. Fixes: 49110a8ce654 ("ksmbd: validate owner of durable handle on reconnect") Assisted-by: Henry (Claude):claude-opus-4 Signed-off-by: Gil Portnoy Co-developed-by: Namjae Jeon Signed-off-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Sasha Levin --- fs/smb/server/vfs_cache.c | 29 +++++++++++++++++++++-------- 1 file changed, 21 insertions(+), 8 deletions(-) diff --git a/fs/smb/server/vfs_cache.c b/fs/smb/server/vfs_cache.c index a1f59a8e16e281..fad426fe3d14d6 100644 --- a/fs/smb/server/vfs_cache.c +++ b/fs/smb/server/vfs_cache.c @@ -980,16 +980,21 @@ void ksmbd_stop_durable_scavenger(void) static int ksmbd_vfs_copy_durable_owner(struct ksmbd_file *fp, struct ksmbd_user *user) { + char *name; + if (!user) return -EINVAL; /* Duplicate the user name to ensure identity persistence */ - fp->owner.name = kstrdup(user->name, GFP_KERNEL); - if (!fp->owner.name) + name = kstrdup(user->name, GFP_KERNEL); + if (!name) return -ENOMEM; + spin_lock(&fp->f_lock); fp->owner.uid = user->uid; fp->owner.gid = user->gid; + fp->owner.name = name; + spin_unlock(&fp->f_lock); return 0; } @@ -1007,18 +1012,24 @@ static int ksmbd_vfs_copy_durable_owner(struct ksmbd_file *fp, bool ksmbd_vfs_compare_durable_owner(struct ksmbd_file *fp, struct ksmbd_user *user) { - if (!user || !fp->owner.name) + bool ret = false; + + if (!user) return false; + spin_lock(&fp->f_lock); + if (!fp->owner.name) + goto out; + /* Check if the UID and GID match first (fast path) */ if (fp->owner.uid != user->uid || fp->owner.gid != user->gid) - return false; + goto out; /* Validate the account name to ensure the same SecurityContext */ - if (strcmp(fp->owner.name, user->name)) - return false; - - return true; + ret = (strcmp(fp->owner.name, user->name) == 0); +out: + spin_unlock(&fp->f_lock); + return ret; } static bool session_fd_check(struct ksmbd_tree_connect *tcon, @@ -1172,9 +1183,11 @@ int ksmbd_reopen_durable_fd(struct ksmbd_work *work, struct ksmbd_file *fp) } up_write(&ci->m_lock); + spin_lock(&fp->f_lock); fp->owner.uid = fp->owner.gid = 0; kfree(fp->owner.name); fp->owner.name = NULL; + spin_unlock(&fp->f_lock); return 0; } -- 2.53.0