From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 4565A3A7F49 for ; Fri, 20 Mar 2026 11:29:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774006184; cv=none; b=iaDi4cjc1EYIY6FT+cwgYKI2frMHJ8dCBkfh2hDr9Ihq+7MKueGDJUryDfYmXwZcAznARjxiPgJ5aW3tVv3Nd7QXFHDlkQJXjEBiVE+Al7eE7rCiKLHvGrfqnBEKObnsZmQKL9pmIVpbDohyPFLf0rm3xsWynVFH09M1CZe0YyY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774006184; c=relaxed/simple; bh=sRKgGCyGi43IkDBU2lpcsq+RqJLxVxyMeg3WUy1Pt+A=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=da5SF5wBvxd1eblr4QOtivWZVa8Km8p22/8eQNVtN41+nk2//YGFpfF7utTu8URtYNDS+70zQLQxiGu8Q8dv7PsPjKlkjmslgzUlJNU8FTBPN1YpZ4ZpO0qrZ8JtlWYTALbjRKulUTnn2xofWvW8m9ZIvgwutJkZN1fco/zOoaY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Xj3dZvDb; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Xj3dZvDb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 33808C2BCAF; Fri, 20 Mar 2026 11:29:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774006183; bh=sRKgGCyGi43IkDBU2lpcsq+RqJLxVxyMeg3WUy1Pt+A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Xj3dZvDbIpEeFcYYC3P9LgeiPONoQY9Xyq2ob4tkGtJh3O5N9kD3yRkv2L6d2xy+4 1ASqCYXx85GYvEoM40amgFtlIHDHHta1WBZivwdHXxZ/lEniJs5ZRoNudG1pR8x2Dk 8zxvAg4li8WwNT66xC2YXP3FKIj+c1xnh9VWwc5kiXEQ4kaIJtRG5Eqyc+KHxpP1/j cyTNOMQf2iNN5cxLCIj1sgwnOnJ5nBUHGduDIYcHn6GF1+Z609mpjIYFbNNwlMmF6W iC8mUq/MO5biL1BW35j7roB+uHHPN5AtgvPjM8IbKor/Da+IKXRQ1GzsJXh+8m8ExC BjzmHLy+L4FMw== From: Sasha Levin To: stable@vger.kernel.org Cc: Chuck Lever , Misbah Anjum N , Jeff Layton , NeilBrown , Olga Kornievskaia , Sasha Levin Subject: [PATCH 5.15.y 2/2] NFSD: Hold net reference for the lifetime of /proc/fs/nfs/exports fd Date: Fri, 20 Mar 2026 07:29:40 -0400 Message-ID: <20260320112940.3960556-2-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260320112940.3960556-1-sashal@kernel.org> References: <2026032038-dimly-tiring-d92b@gregkh> <20260320112940.3960556-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Chuck Lever [ Upstream commit e7fcf179b82d3a3730fd8615da01b087cc654d0b ] The /proc/fs/nfs/exports proc entry is created at module init and persists for the module's lifetime. exports_proc_open() captures the caller's current network namespace and stores its svc_export_cache in seq->private, but takes no reference on the namespace. If the namespace is subsequently torn down (e.g. container destruction after the opener does setns() to a different namespace), nfsd_net_exit() calls nfsd_export_shutdown() which frees the cache. Subsequent reads on the still-open fd dereference the freed cache_detail, walking a freed hash table. Hold a reference on the struct net for the lifetime of the open file descriptor. This prevents nfsd_net_exit() from running -- and thus prevents nfsd_export_shutdown() from freeing the cache -- while any exports fd is open. cache_detail already stores its net pointer (cd->net, set by cache_create_net()), so exports_release() can retrieve it without additional per-file storage. Reported-by: Misbah Anjum N Closes: https://lore.kernel.org/linux-nfs/dcd371d3a95815a84ba7de52cef447b8@linux.ibm.com/ Fixes: 96d851c4d28d ("nfsd: use proper net while reading "exports" file") Cc: stable@vger.kernel.org Reviewed-by: Jeff Layton Reviewed-by: NeilBrown Tested-by: Olga Kornievskaia Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin --- fs/nfsd/nfsctl.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c index e3d34fb7fce5a..bc30cf413c92e 100644 --- a/fs/nfsd/nfsctl.c +++ b/fs/nfsd/nfsctl.c @@ -152,9 +152,19 @@ static int exports_net_open(struct net *net, struct file *file) seq = file->private_data; seq->private = nn->svc_export_cache; + get_net(net); return 0; } +static int exports_release(struct inode *inode, struct file *file) +{ + struct seq_file *seq = file->private_data; + struct cache_detail *cd = seq->private; + + put_net(cd->net); + return seq_release(inode, file); +} + static int exports_nfsd_open(struct inode *inode, struct file *file) { return exports_net_open(inode->i_sb->s_fs_info, file); @@ -164,7 +174,7 @@ static const struct file_operations exports_nfsd_operations = { .open = exports_nfsd_open, .read = seq_read, .llseek = seq_lseek, - .release = seq_release, + .release = exports_release, }; static int export_features_show(struct seq_file *m, void *v) @@ -1421,7 +1431,7 @@ static const struct proc_ops exports_proc_ops = { .proc_open = exports_proc_open, .proc_read = seq_read, .proc_lseek = seq_lseek, - .proc_release = seq_release, + .proc_release = exports_release, }; static int create_proc_exports_entry(void) -- 2.51.0