Hi Sergey,
On 8/23/24 4:32 PM, Sergey Shtylyov wrote:
> The nfs_client::cl_lease_time field (as well as the jiffies variable it's
> used with) is declared as *unsigned long*, which is 32-bit type on 32-bit
> arches and 64-bit type on 64-bit arches. When nfs4_set_lease_period() that
> sets nfs_client::cl_lease_time is called, 32-bit nfs_fsinfo::lease_time
> field is multiplied by HZ -- that might overflow *unsigned long* on 32-bit
> arches. Actually, there's no need to multiply by HZ at all the call sites
> of nfs4_set_lease_period() -- it makes more sense to do that once, inside
> that function (using mul_u32_u32(), as it produces a better code on 32-bit
> x86 arch), also checking for an overflow there and returning -ERANGE if it
> does happen (we're also making that function *int* instead of *void* and
> adding the result checks to its callers)...
>
> Found by Linux Verification Center (linuxtesting.org) with the Svace static
> analysis tool.
>
> Signed-off-by: Sergey Shtylyov <s.shtylyov@xxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
>
> ---
> This patch is against the master branch of Trond Myklebust's linux-nfs.git repo.
>
> fs/nfs/nfs4_fs.h | 3 +--
> fs/nfs/nfs4proc.c | 3 ++-
> fs/nfs/nfs4renewd.c | 13 ++++++++++---
> fs/nfs/nfs4state.c | 4 +++-
> 4 files changed, 16 insertions(+), 7 deletions(-)
>
> Index: linux-nfs/fs/nfs/nfs4_fs.h
> ===================================================================
> --- linux-nfs.orig/fs/nfs/nfs4_fs.h
> +++ linux-nfs/fs/nfs/nfs4_fs.h
> @@ -464,8 +464,7 @@ struct nfs_client *nfs4_alloc_client(con
> extern void nfs4_schedule_state_renewal(struct nfs_client *);
> extern void nfs4_kill_renewd(struct nfs_client *);
> extern void nfs4_renew_state(struct work_struct *);
> -extern void nfs4_set_lease_period(struct nfs_client *clp, unsigned long lease);
> -
> +extern int nfs4_set_lease_period(struct nfs_client *clp, u32 period);
>
> /* nfs4state.c */
> extern const nfs4_stateid current_stateid;
> Index: linux-nfs/fs/nfs/nfs4proc.c
> ===================================================================
> --- linux-nfs.orig/fs/nfs/nfs4proc.c
> +++ linux-nfs/fs/nfs/nfs4proc.c
> @@ -5403,7 +5403,8 @@ static int nfs4_do_fsinfo(struct nfs_ser
> err = _nfs4_do_fsinfo(server, fhandle, fsinfo);
> trace_nfs4_fsinfo(server, fhandle, fsinfo->fattr, err);
> if (err == 0) {
> - nfs4_set_lease_period(server->nfs_client, fsinfo->lease_time * HZ);
> + err = nfs4_set_lease_period(server->nfs_client,
> + fsinfo->lease_time);
> break;
> }
> err = nfs4_handle_exception(server, err, &exception);
> Index: linux-nfs/fs/nfs/nfs4renewd.c
> ===================================================================
> --- linux-nfs.orig/fs/nfs/nfs4renewd.c
> +++ linux-nfs/fs/nfs/nfs4renewd.c
> @@ -137,15 +137,22 @@ nfs4_kill_renewd(struct nfs_client *clp)
> * nfs4_set_lease_period - Sets the lease period on a nfs_client
> *
> * @clp: pointer to nfs_client
> - * @lease: new value for lease period
> + * @period: new value for lease period (in seconds)
> */
> -void nfs4_set_lease_period(struct nfs_client *clp,
> - unsigned long lease)
> +int nfs4_set_lease_period(struct nfs_client *clp, u32 period)
> {
> + u64 result = mul_u32_u32(period, HZ);
Thanks for the patch! Sorry it took a couple of weeks for me to look at. I do like this change for doing the calculation in a single place, rather than relying on callers to do it first.
> + unsigned long lease = result;
> +
> + /* First see if period * HZ actually fits into unsigned long... */
> + if (result > ULONG_MAX)
> + return -ERANGE;
However, I'm not sold that this should be an error condition. I wonder if it would be better to change the clp->cl_lease_time field to a u64 so it has the same size on 32bit and 64bit architectures?
Thanks,
Anna
> +
> spin_lock(&clp->cl_lock);
> clp->cl_lease_time = lease;
> spin_unlock(&clp->cl_lock);
>
> /* Cap maximum reconnect timeout at 1/2 lease period */
> rpc_set_connect_timeout(clp->cl_rpcclient, lease, lease >> 1);
> + return 0;
> }
> Index: linux-nfs/fs/nfs/nfs4state.c
> ===================================================================
> --- linux-nfs.orig/fs/nfs/nfs4state.c
> +++ linux-nfs/fs/nfs/nfs4state.c
> @@ -103,7 +103,9 @@ static int nfs4_setup_state_renewal(stru
>
> status = nfs4_proc_get_lease_time(clp, &fsinfo);
> if (status == 0) {
> - nfs4_set_lease_period(clp, fsinfo.lease_time * HZ);
> + status = nfs4_set_lease_period(clp, fsinfo.lease_time);
> + if (status)
> + return status;
> nfs4_schedule_state_renewal(clp);
> }
>
