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 7BA862D9ECA for ; Thu, 19 Feb 2026 21:50:23 +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=1771537823; cv=none; b=lekDxPMIwuQdY00g2nPXSGhw9kY5JtlrYINdOwwqH9VaNaerAogu0SdC809YDC5AQ6m86ZxtktK8D4knMwSkPGpbKUxtZEZ3fG0u8vO87nwV/SRgJl3Ib/B8Q789sd3FQGnN+iGmETJ0JEkRxyc5Chc3x6/Uf+3UfipICoQJ5bY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771537823; c=relaxed/simple; bh=IChiNIHlILaC77jNRymiDzluSmdql9OoUtFgHB0wuqo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BfN8bzNfiOBvkP5G1+RxQvQ5uzszxB6tVmJGoXG/TyOysLLsgd0Nc3EVy1Rud+wNq2wdLTx1F1YVfgEhUQFO8uSbVmvLDyRhsUK+295IEBbgXfKg+LKeF6syqDkejtJpMb8mBi9STRe2YCr46DqyM0z3Nyr7lTsKpXv4u9kJk64= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PyRHUgsp; 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="PyRHUgsp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7535CC4CEF7; Thu, 19 Feb 2026 21:50:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771537823; bh=IChiNIHlILaC77jNRymiDzluSmdql9OoUtFgHB0wuqo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PyRHUgsp9WfgOYS1GBgvwdhSfBB7c3HZh4ZliNLBTM6VrBbCzUjjZYg4BHvrA5mKC 1cKFoJieixC+cUbGiqMoTKpDWYOAIMP6b+u9HnUDo545Bgn1+zSvA+8QCJF+6pKtWq zPn79gZMG3WolyecSkiieTcxowHx/zVRrCR+IOm6tRpSVKFf15O+N9tT/jHG09WQs2 XxzylvdRMhYwefaW8daDgfiGzXiDRKFOhU3/gXhasQc2gFmDrTjDAFzxzggQnyZ6Xw 6tMoJAalJHePXA2gbedGXULOCNSJgLIRWOhJ0plbUYNZh6D9K2WJKrQiqgd27l4h3n iKj56Po4wbZDg== From: Chuck Lever To: misanjum@linux.ibm.com, NeilBrown , Jeff Layton , Olga Kornievskaia , Dai Ngo , Tom Talpey Cc: , Chuck Lever Subject: [PATCH v1 2/2] NFSD: Hold net reference for the lifetime of /proc/fs/nfs/exports fd Date: Thu, 19 Feb 2026 16:50:17 -0500 Message-ID: <20260219215017.1769-3-cel@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260219215017.1769-1-cel@kernel.org> References: <20260219215017.1769-1-cel@kernel.org> Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Chuck Lever 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") Signed-off-by: Chuck Lever --- 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 4166f59908f4..3d5a676e1d14 100644 --- a/fs/nfsd/nfsctl.c +++ b/fs/nfsd/nfsctl.c @@ -149,9 +149,19 @@ 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); @@ -161,7 +171,7 @@ 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) @@ -1376,7 +1386,7 @@ 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) -- 2.53.0