Commit e6faac3f authored Jan 31, 2022 by Chuck Lever

NFSD: Fix ia_size underflow



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@vger.kernel.org
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

parent 0cb4d23a

fs/nfsd/vfs.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -435,6 +435,10 @@ nfsd_setattr(struct svc_rqst rqstp, struct svc_fh fhp, struct iattr *iap,
		.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;