From d497ab975141666e674e7bd8729e00095ec23c9d Mon Sep 17 00:00:00 2001 From: Weston Andros Adamson Date: Mon, 6 May 2013 17:12:13 -0400 Subject: [PATCH] NFSv3: match sec= flavor against server list MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Older linux clients match the 'sec=' mount option flavor against the server's flavor list (if available) and return EPERM if the specified flavor or AUTH_NULL (which "matches" any flavor) is not found. Recent changes skip this step and allow the vfs mount even though no operations will succeed, creating a 'dud' mount. This patch reverts back to the old behavior of matching specified flavors against the server list and also returns EPERM when no sec= is specified and none of the flavors returned by the server are supported by the client. Example of behavior change: the server's /etc/exports: /export/krb5 *(sec=krb5,rw,no_root_squash) old client behavior: $ uname -a Linux one.apikia.fake 3.8.8-202.fc18.x86_64 #1 SMP Wed Apr 17 23:25:17 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux $ sudo mount -v -o sec=sys,vers=3 zero:/export/krb5 /mnt mount.nfs: timeout set for Sun May 5 17:32:04 2013 mount.nfs: trying text-based options 'sec=sys,vers=3,addr=192.168.100.10' mount.nfs: prog 100003, trying vers=3, prot=6 mount.nfs: trying 192.168.100.10 prog 100003 vers 3 prot TCP port 2049 mount.nfs: prog 100005, trying vers=3, prot=17 mount.nfs: trying 192.168.100.10 prog 100005 vers 3 prot UDP port 20048 mount.nfs: mount(2): Permission denied mount.nfs: access denied by server while mounting zero:/export/krb5 recently changed behavior: $ uname -a Linux one.apikia.fake 3.9.0-testing+ #2 SMP Fri May 3 20:29:32 EDT 2013 x86_64 x86_64 x86_64 GNU/Linux $ sudo mount -v -o sec=sys,vers=3 zero:/export/krb5 /mnt mount.nfs: timeout set for Sun May 5 17:37:17 2013 mount.nfs: trying text-based options 'sec=sys,vers=3,addr=192.168.100.10' mount.nfs: prog 100003, trying vers=3, prot=6 mount.nfs: trying 192.168.100.10 prog 100003 vers 3 prot TCP port 2049 mount.nfs: prog 100005, trying vers=3, prot=17 mount.nfs: trying 192.168.100.10 prog 100005 vers 3 prot UDP port 20048 $ ls /mnt ls: cannot open directory /mnt: Permission denied $ sudo ls /mnt ls: cannot open directory /mnt: Permission denied $ sudo df /mnt df: ‘/mnt’: Permission denied df: no file systems processed $ sudo umount /mnt $ Signed-off-by: Weston Andros Adamson Signed-off-by: Trond Myklebust --- fs/nfs/super.c | 48 +++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 41 insertions(+), 7 deletions(-) diff --git a/fs/nfs/super.c b/fs/nfs/super.c index 3bb8318f6d0c..b65001c0a119 100644 --- a/fs/nfs/super.c +++ b/fs/nfs/super.c @@ -1607,16 +1607,15 @@ out_security_failure: /* * Select a security flavor for this mount. The selected flavor * is planted in args->auth_flavors[0]. + * + * Returns 0 on success, -EACCES on failure. */ -static void nfs_select_flavor(struct nfs_parsed_mount_data *args, +static int nfs_select_flavor(struct nfs_parsed_mount_data *args, struct nfs_mount_request *request) { unsigned int i, count = *(request->auth_flav_len); rpc_authflavor_t flavor; - if (args->auth_flavors[0] != RPC_AUTH_MAXFLAVOR) - goto out; - /* * The NFSv2 MNT operation does not return a flavor list. */ @@ -1630,6 +1629,25 @@ static void nfs_select_flavor(struct nfs_parsed_mount_data *args, if (count == 0) goto out_default; + /* + * If the sec= mount option is used, the specified flavor or AUTH_NULL + * must be in the list returned by the server. + * + * AUTH_NULL has a special meaning when it's in the server list - it + * means that the server will ignore the rpc creds, so any flavor + * can be used. + */ + if (args->auth_flavors[0] != RPC_AUTH_MAXFLAVOR) { + for (i = 0; i < count; i++) { + if (args->auth_flavors[0] == request->auth_flavs[i] || + request->auth_flavs[i] == RPC_AUTH_NULL) + goto out; + } + dfprintk(MOUNT, "NFS: auth flavor %d not supported by server\n", + args->auth_flavors[0]); + goto out_err; + } + /* * RFC 2623, section 2.7 suggests we SHOULD prefer the * flavor listed first. However, some servers list @@ -1650,12 +1668,29 @@ static void nfs_select_flavor(struct nfs_parsed_mount_data *args, } } + /* + * As a last chance, see if the server list contains AUTH_NULL - + * if it does, use the default flavor. + */ + for (i = 0; i < count; i++) { + if (request->auth_flavs[i] == RPC_AUTH_NULL) + goto out_default; + } + + dfprintk(MOUNT, "NFS: no auth flavors in common with server\n"); + goto out_err; + out_default: - flavor = RPC_AUTH_UNIX; + /* use default if flavor not already set */ + flavor = (args->auth_flavors[0] == RPC_AUTH_MAXFLAVOR) ? + RPC_AUTH_UNIX : args->auth_flavors[0]; out_set: args->auth_flavors[0] = flavor; out: dfprintk(MOUNT, "NFS: using auth flavor %d\n", args->auth_flavors[0]); + return 0; +out_err: + return -EACCES; } /* @@ -1718,8 +1753,7 @@ static int nfs_request_mount(struct nfs_parsed_mount_data *args, return status; } - nfs_select_flavor(args, &request); - return 0; + return nfs_select_flavor(args, &request); } struct dentry *nfs_try_mount(int flags, const char *dev_name, -- 2.20.1