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 DB2F54A6CF9 for ; Thu, 3 Sep 2026 13:07:09 +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=1788440832; cv=none; b=U8jict/wttfm8+tkAQQ7juKhLwac8fh+De0QYuD67Qh3/z9HjzevEzX+qldEOaiOk2xFk6LFWlTVq2l1jAbiZVEbgAlUhl9ulNGZpniLaj6jFvwP1oXEmR6Ek2yvFhjVhqh1EfaPUrMLwG6bYLMaLbMcMEnlxX+Zfd7NJTkSN28= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788440832; c=relaxed/simple; bh=zrpmo1sHh+vYuDtcid6WImdUQ28PL5mDzanyLXqOxPA=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=qj76sm3+R5aDKPOqXcJPxMUPnQMn+4/aKTQW/9X6MhdreDZk97njUBi0CxciYfmxF8fJrPPN9C46iMaSK4HkjEPrcOYgC56MT8ArsxpMhP3TvNSia8LCkhiZrKwbyIbIc5ObDQ/QY9/YSeEmYzm5omi+qhr07+nn009jGP+MuRE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=o48GdHgj; 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="o48GdHgj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EC77D1F00A3E; Thu, 3 Sep 2026 13:07:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788440827; bh=ocfBiK4prX8NKb/SM7E/I873S6uHEY8775599uOFds0=; h=Subject:To:Cc:From:Date; b=o48GdHgjWYjiFdYqVfB+vInNMw/xqidiguS6TuHmcfE8anax1c9sA8RfguO6X+VWs 5AE7Qq5cs1kXoDn2SED7a6+aFAELSwQNn767CWbvppY+48VygDZ5CG5jbCVn+LOIGR Z0TvcFE4i6qjMyDkuInIJf735p1EUUM5e3mlthsg= Subject: FAILED: patch "[PATCH] NFSD: check truncate permission under inode lock" failed to apply to 5.10-stable tree To: cel@kernel.org,chuck.lever@oracle.com,clm@meta.com,jlayton@kernel.org Cc: From: Date: Thu, 03 Sep 2026 15:02:40 +0200 Message-ID: <2026090340-darkness-disposal-745f@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y git checkout FETCH_HEAD git cherry-pick -x b778e0e0a16759f22a70579c3cf8d254a40d4a7f # git commit -s git send-email --to '' --in-reply-to '2026090340-darkness-disposal-745f@gregkh' --subject-prefix 'PATCH 5.10.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From b778e0e0a16759f22a70579c3cf8d254a40d4a7f Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Sat, 30 May 2026 09:19:22 -0400 Subject: [PATCH] NFSD: check truncate permission under inode lock nfsd_setattr() checks whether a size update needs NFSD_MAY_TRUNC before it takes inode_lock(). The comparison uses the file size sampled by that unlocked read, but the actual ATTR_SIZE update is applied later under inode_lock() by notify_change(). This leaves a TOCTOU window for append-only files. If a client sends a SETATTR that does not shrink the file at the time of the unlocked sample, a concurrent append can extend the file before nfsd_setattr() takes inode_lock(). notify_change() then applies a real truncation without the NFSD_MAY_TRUNC check that rejects IS_APPEND(inode). The VFS truncate syscall paths perform their own append-only checks before calling notify_change(), so NFSD must make this decision against the locked size it is about to change. Split the write-count acquisition from the truncation permission check. Keep get_write_access() before the locked setattr work, then recheck whether the requested size is below i_size_read(inode) after inode_lock() has been acquired and before notify_change(ATTR_SIZE). This also avoids the plain unlocked inode->i_size load. Fixes: 783112f7401f ("nfsd: special case truncates some more") Cc: stable@vger.kernel.org Assisted-by: kres:claude-opus-4-7 Reported-by: Chris Mason Signed-off-by: Jeff Layton Link: https://patch.msgid.link/20260530-nfsd-fixes-v2-6-f27e8eb4d974@kernel.org Signed-off-by: Chuck Lever diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index 1e89c7ff9493..a3940548136f 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -419,21 +419,22 @@ nfsd_sanitize_attrs(struct inode *inode, struct iattr *iap) } static __be32 -nfsd_get_write_access(struct svc_rqst *rqstp, struct svc_fh *fhp, - struct iattr *iap) +nfsd_may_truncate(struct svc_rqst *rqstp, struct svc_fh *fhp, + struct iattr *iap) { struct inode *inode = d_inode(fhp->fh_dentry); - if (iap->ia_size < inode->i_size) { - __be32 err; + if (iap->ia_size >= i_size_read(inode)) + return nfs_ok; - err = nfsd_permission(&rqstp->rq_cred, - fhp->fh_export, fhp->fh_dentry, - NFSD_MAY_TRUNC | NFSD_MAY_OWNER_OVERRIDE); - if (err) - return err; - } - return nfserrno(get_write_access(inode)); + return nfsd_permission(&rqstp->rq_cred, fhp->fh_export, fhp->fh_dentry, + NFSD_MAY_TRUNC | NFSD_MAY_OWNER_OVERRIDE); +} + +static __be32 +nfsd_get_write_access(struct svc_fh *fhp) +{ + return nfserrno(get_write_access(d_inode(fhp->fh_dentry))); } static int __nfsd_setattr(struct dentry *dentry, struct iattr *iap) @@ -560,12 +561,17 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, * setattr call. */ if (size_change) { - err = nfsd_get_write_access(rqstp, fhp, iap); + err = nfsd_get_write_access(fhp); if (err) return err; } inode_lock(inode); + if (size_change) { + err = nfsd_may_truncate(rqstp, fhp, iap); + if (err) + goto out_unlock; + } err = fh_fill_pre_attrs(fhp); if (err) goto out_unlock;