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 CBA1939A7E0 for ; Fri, 20 Mar 2026 11:39:42 +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=1774006782; cv=none; b=CAA+KaJ+MyxshE/ItFs350JiSiasYQJC4xLCbMy0NcqQ07cc2CLU2VtKcyUM/HgmD2h3j+StWxvl1mERlzypeVuz0KtkN0zerWanFI+nNtCi/LOCByuKkEp0XMGWp0yK2vF1LaYRwwyn6uu8jzs0JwqvspGRug+sHBRfHi5rrro= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774006782; c=relaxed/simple; bh=6KI421U9CRdcz8Oj2SVET3aBDs+dyQUe7NEaZfoVEeI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=J0aT8e7KFZpLROPumOHyKR/Ovu5SJ9tX7LhnC7FbK1ycTA7HWBkPfrBrsoF+2fGAc5APtuXQODS2AdnJpcVoLYfJEt046U7mZwsArc6/J3MTmz4uLN3J02wLiDlhFsTaaRJQnAeoES2+lVIkzYlDD/lGG5SvAqv9ZAHmIOhhl9Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=imTzkuJf; 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="imTzkuJf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D4BFCC2BC9E; Fri, 20 Mar 2026 11:39:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774006782; bh=6KI421U9CRdcz8Oj2SVET3aBDs+dyQUe7NEaZfoVEeI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=imTzkuJfrdgfIwbboaWTJ0+4FL1RFU1mucaJNo5g6IkN1LV5tZpZx2ropbA0Xp9gt sEpeVES03YoJ1WgoRhbf+fzw1Zp6qWKe/QZssXTRS2dywmXls95ioDYgX6/2gXnHWp psG2Dg8CezQcQYCdeRTzMKm7OD9uCjBg5OibyG9rTDT4+r2Er0sOGrzJBzjAhfG+bF Ogdb9TNXsIOlifwPTCJ+Pqbk2V/21uZodmdxoh1MJtgklSz8OFdYRBZOAsQGDvdgh+ lV8tjtyeRQX2zgZA6UuMiFHKJl3vvfh9efh3meQqNJgmLhe0DdltMFbhhUrYJdxrOP jXyBvm2ljwxCg== From: Sasha Levin To: stable@vger.kernel.org Cc: Chuck Lever , Misbah Anjum N , Jeff Layton , NeilBrown , Olga Kornievskaia , Sasha Levin Subject: [PATCH 5.10.y 2/2] NFSD: Hold net reference for the lifetime of /proc/fs/nfs/exports fd Date: Fri, 20 Mar 2026 07:39:39 -0400 Message-ID: <20260320113939.3971291-2-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260320113939.3971291-1-sashal@kernel.org> References: <2026032042-stalling-batboy-6b82@gregkh> <20260320113939.3971291-1-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 ad7a3909ae6df..8178d7d016487 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