This looks right, thanks, it's just waiting on testing--the latest
Fedora update seems to have broken my test rig's krb5 server, hopefully
I'll get that back up tommorrow.
--b.
On Fri, May 18, 2018 at 05:13:04PM -0400, Dave Wysochanski wrote:
> There is a 16-byte memory leak inside sunrpc/auth_gss on an nfs server when
> a client mounts with 'sec=krb5' in a simple mount / umount loop. The leak
> is seen by either monitoring the kmalloc-16 slab or with kmemleak enabled
>
> unreferenced object 0xffff92e6a045f030 (size 16):
> comm "nfsd", pid 1096, jiffies 4294936658 (age 761.110s)
> hex dump (first 16 bytes):
> 2a 86 48 86 f7 12 01 02 02 00 00 00 00 00 00 00 *.H.............
> backtrace:
> [<000000004b2b79a7>] gssx_dec_buffer+0x79/0x90 [auth_rpcgss]
> [<000000002610ac1a>] gssx_dec_accept_sec_context+0x215/0x6dd [auth_rpcgss]
> [<000000004fd0e81d>] rpcauth_unwrap_resp+0xa9/0xe0 [sunrpc]
> [<000000002b099233>] call_decode+0x1e9/0x840 [sunrpc]
> [<00000000954fc846>] __rpc_execute+0x80/0x3f0 [sunrpc]
> [<00000000c83a961c>] rpc_run_task+0x10d/0x150 [sunrpc]
> [<000000002c2cdcd2>] rpc_call_sync+0x4d/0xa0 [sunrpc]
> [<000000000b74eea2>] gssp_accept_sec_context_upcall+0x196/0x470 [auth_rpcgss]
> [<000000003271273f>] svcauth_gss_proxy_init+0x188/0x520 [auth_rpcgss]
> [<000000001cf69f01>] svcauth_gss_accept+0x3a6/0xb50 [auth_rpcgss]
>
> If you map the above to code you'll see the following call chain
> gssx_dec_accept_sec_context
> gssx_dec_ctx (missing from kmemleak output)
> gssx_dec_buffer(xdr, &ctx->mech)
>
> Inside gssx_dec_buffer there is 'kmemdup' where we allocate memory for
> any gssx_buffer (buf) and store into buf->data. In the above instance,
> 'buf == &ctx->mech).
>
> Further up in the chain in gssp_accept_sec_context_upcall we see ctx->mech
> is part of a stack variable 'struct gssx_ctx rctxh'. Now later inside
> gssp_accept_sec_context_upcall after gssp_call, there is a number of
> memcpy and kfree statements, but there is no kfree(rctxh.mech.data)
> after the memcpy into data->mech_oid.data.
>
> With this patch applied and the same mount / unmount loop, the kmalloc-16
> slab is stable and kmemleak enabled no longer shows the above backtrace.
>
> Signed-off-by: Dave Wysochanski <dwysocha@xxxxxxxxxx>
> ---
> net/sunrpc/auth_gss/gss_rpc_upcall.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/sunrpc/auth_gss/gss_rpc_upcall.c b/net/sunrpc/auth_gss/gss_rpc_upcall.c
> index 46b295e..d98e2b6 100644
> --- a/net/sunrpc/auth_gss/gss_rpc_upcall.c
> +++ b/net/sunrpc/auth_gss/gss_rpc_upcall.c
> @@ -298,9 +298,11 @@ int gssp_accept_sec_context_upcall(struct net *net,
> if (res.context_handle) {
> data->out_handle = rctxh.exported_context_token;
> data->mech_oid.len = rctxh.mech.len;
> - if (rctxh.mech.data)
> + if (rctxh.mech.data) {
> memcpy(data->mech_oid.data, rctxh.mech.data,
> data->mech_oid.len);
> + kfree(rctxh.mech.data);
> + }
> client_name = rctxh.src_name.display_name;
> }
>
> --
> 1.8.3.1
>
> --
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