linux-kernel - [PATCH 5.15 014/172] NFSD: Fix ia

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Date:   Mon, 14 Feb 2022 10:24:32 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Chuck Lever <chuck.lever@...cle.com>
Subject: [PATCH 5.15 014/172] NFSD: Fix ia_size underflow

From: Chuck Lever <chuck.lever@...cle.com>

commit e6faac3f58c7c4176b66f63def17a34232a17b0e upstream.

iattr::ia_size is a loff_t, which is a signed 64-bit type. NFSv3 and
NFSv4 both define file size as an unsigned 64-bit type. Thus there
is a range of valid file size values an NFS client can send that is
already larger than Linux can handle.

Currently decode_fattr4() dumps a full u64 value into ia_size. If
that value happens to be larger than S64_MAX, then ia_size
underflows. I'm about to fix up the NFSv3 behavior as well, so let's
catch the underflow in the common code path: nfsd_setattr().

Cc: stable@...r.kernel.org
Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/nfsd/vfs.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -433,6 +433,10 @@ nfsd_setattr(struct svc_rqst *rqstp, str
 			.ia_size	= iap->ia_size,
 		};

+		host_err = -EFBIG;
+		if (iap->ia_size < 0)
+			goto out_unlock;
+
 		host_err = notify_change(&init_user_ns, dentry, &size_attr, NULL);
 		if (host_err)
 			goto out_unlock;