From a319268891089386bd303bb90ace89d75e47102f Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Tue, 9 Jun 2015 19:43:59 -0400 Subject: [PATCH] nfs: make nfs4_init_nonuniform_client_string use a dynamically allocated buffer The way the *_client_string functions work is a little goofy. They build the string in an on-stack buffer and then use kstrdup to copy it. This is not only stack-heavy but artificially limits the size of the client name string. Change it so that we determine the length of the string, allocate it and then scnprintf into it. Since the contents of the nonuniform string depend on rcu-managed data structures, it's possible that they'll change between when we allocate the string and when we go to fill it. If that happens, free the string, recalculate the length and try again. If it the mismatch isn't resolved on the second try then just give up and return -EINVAL. Signed-off-by: Jeff Layton Signed-off-by: Trond Myklebust --- fs/nfs/nfs4proc.c | 74 ++++++++++++++++++++++++++++++++--------------- 1 file changed, 51 insertions(+), 23 deletions(-) diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index b2afe9556147..c20322636a68 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -4957,25 +4957,54 @@ static void nfs4_init_boot_verifier(const struct nfs_client *clp, memcpy(bootverf->data, verf, sizeof(bootverf->data)); } -static unsigned int -nfs4_init_nonuniform_client_string(struct nfs_client *clp, - char *buf, size_t len) +static int +nfs4_init_nonuniform_client_string(struct nfs_client *clp) { - unsigned int result; + int result; + size_t len; + char *str; + bool retried = false; if (clp->cl_owner_id != NULL) - return strlcpy(buf, clp->cl_owner_id, len); + return 0; +retry: + rcu_read_lock(); + len = 10 + strlen(clp->cl_ipaddr) + 1 + + strlen(rpc_peeraddr2str(clp->cl_rpcclient, RPC_DISPLAY_ADDR)) + + 1 + + strlen(rpc_peeraddr2str(clp->cl_rpcclient, RPC_DISPLAY_PROTO)) + + 1; + rcu_read_unlock(); + + if (len > NFS4_OPAQUE_LIMIT + 1) + return -EINVAL; + + /* + * Since this string is allocated at mount time, and held until the + * nfs_client is destroyed, we can use GFP_KERNEL here w/o worrying + * about a memory-reclaim deadlock. + */ + str = kmalloc(len, GFP_KERNEL); + if (!str) + return -ENOMEM; rcu_read_lock(); - result = scnprintf(buf, len, "Linux NFSv4.0 %s/%s %s", - clp->cl_ipaddr, - rpc_peeraddr2str(clp->cl_rpcclient, - RPC_DISPLAY_ADDR), - rpc_peeraddr2str(clp->cl_rpcclient, - RPC_DISPLAY_PROTO)); + result = scnprintf(str, len, "Linux NFSv4.0 %s/%s %s", + clp->cl_ipaddr, + rpc_peeraddr2str(clp->cl_rpcclient, RPC_DISPLAY_ADDR), + rpc_peeraddr2str(clp->cl_rpcclient, RPC_DISPLAY_PROTO)); rcu_read_unlock(); - clp->cl_owner_id = kstrdup(buf, GFP_KERNEL); - return result; + + /* Did something change? */ + if (result >= len) { + kfree(str); + if (retried) + return -EINVAL; + retried = true; + goto retry; + } + clp->cl_owner_id = str; + return 0; } static unsigned int @@ -5066,20 +5095,19 @@ int nfs4_proc_setclientid(struct nfs_client *clp, u32 program, /* nfs_client_id4 */ nfs4_init_boot_verifier(clp, &sc_verifier); - if (test_bit(NFS_CS_MIGRATION, &clp->cl_flags)) + if (test_bit(NFS_CS_MIGRATION, &clp->cl_flags)) { setclientid.sc_name_len = nfs4_init_uniform_client_string(clp, setclientid.sc_name, sizeof(setclientid.sc_name)); - else - setclientid.sc_name_len = - nfs4_init_nonuniform_client_string(clp, - setclientid.sc_name, - sizeof(setclientid.sc_name)); - - if (!clp->cl_owner_id) { - status = -ENOMEM; - goto out; + if (!clp->cl_owner_id) { + status = -ENOMEM; + goto out; + } + } else { + status = nfs4_init_nonuniform_client_string(clp); + if (status) + goto out; } /* cb_client4 */ -- 2.30.2