From 0070ed3d9ebf6908a36b809def5478092067503c Mon Sep 17 00:00:00 2001 From: Dave Wysochanski Date: Fri, 18 May 2018 17:13:04 -0400 Subject: [PATCH] Fix 16-byte memory leak in gssp_accept_sec_context_upcall 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 Signed-off-by: J. Bruce Fields --- 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; } -- 2.7.4