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(). Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx> --- fs/nfsd/vfs.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index 99c2b9dfbb10..0cccceb105e7 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -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;
