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authorJeff Layton <jlayton@primarydata.com>2014-11-13 07:30:46 -0500
committerTrond Myklebust <trond.myklebust@primarydata.com>2014-11-13 13:15:49 -0500
commitb3ecba096729f521312d1863ad22530695527aed (patch)
tree920fcca552d935bf6029e9c3a69c46967294c5e5 /net/sunrpc/auth_gss
parentf8ebf7a8ca35dde321f0cd385fee6f1950609367 (diff)
downloadlinux-b3ecba096729f521312d1863ad22530695527aed.tar.bz2
sunrpc: fix sleeping under rcu_read_lock in gss_stringify_acceptor
Bruce reported that he was seeing the following BUG pop: BUG: sleeping function called from invalid context at mm/slab.c:2846 in_atomic(): 0, irqs_disabled(): 0, pid: 4539, name: mount.nfs 2 locks held by mount.nfs/4539: #0: (nfs_clid_init_mutex){+.+.+.}, at: [<ffffffffa01c0a9a>] nfs4_discover_server_trunking+0x4a/0x2f0 [nfsv4] #1: (rcu_read_lock){......}, at: [<ffffffffa00e3185>] gss_stringify_acceptor+0x5/0xb0 [auth_rpcgss] Preemption disabled at:[<ffffffff81a4f082>] printk+0x4d/0x4f CPU: 3 PID: 4539 Comm: mount.nfs Not tainted 3.18.0-rc1-00013-g5b095e9 #3393 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 ffff880021499390 ffff8800381476a8 ffffffff81a534cf 0000000000000001 0000000000000000 ffff8800381476c8 ffffffff81097854 00000000000000d0 0000000000000018 ffff880038147718 ffffffff8118e4f3 0000000020479f00 Call Trace: [<ffffffff81a534cf>] dump_stack+0x4f/0x7c [<ffffffff81097854>] __might_sleep+0x114/0x180 [<ffffffff8118e4f3>] __kmalloc+0x1a3/0x280 [<ffffffffa00e31d8>] gss_stringify_acceptor+0x58/0xb0 [auth_rpcgss] [<ffffffffa00e3185>] ? gss_stringify_acceptor+0x5/0xb0 [auth_rpcgss] [<ffffffffa006b438>] rpcauth_stringify_acceptor+0x18/0x30 [sunrpc] [<ffffffffa01b0469>] nfs4_proc_setclientid+0x199/0x380 [nfsv4] [<ffffffffa01b04d0>] ? nfs4_proc_setclientid+0x200/0x380 [nfsv4] [<ffffffffa01bdf1a>] nfs40_discover_server_trunking+0xda/0x150 [nfsv4] [<ffffffffa01bde45>] ? nfs40_discover_server_trunking+0x5/0x150 [nfsv4] [<ffffffffa01c0acf>] nfs4_discover_server_trunking+0x7f/0x2f0 [nfsv4] [<ffffffffa01c8e24>] nfs4_init_client+0x104/0x2f0 [nfsv4] [<ffffffffa01539b4>] nfs_get_client+0x314/0x3f0 [nfs] [<ffffffffa0153780>] ? nfs_get_client+0xe0/0x3f0 [nfs] [<ffffffffa01c83aa>] nfs4_set_client+0x8a/0x110 [nfsv4] [<ffffffffa0069708>] ? __rpc_init_priority_wait_queue+0xa8/0xf0 [sunrpc] [<ffffffffa01c9b2f>] nfs4_create_server+0x12f/0x390 [nfsv4] [<ffffffffa01c1472>] nfs4_remote_mount+0x32/0x60 [nfsv4] [<ffffffff81196489>] mount_fs+0x39/0x1b0 [<ffffffff81166145>] ? __alloc_percpu+0x15/0x20 [<ffffffff811b276b>] vfs_kern_mount+0x6b/0x150 [<ffffffffa01c1396>] nfs_do_root_mount+0x86/0xc0 [nfsv4] [<ffffffffa01c1784>] nfs4_try_mount+0x44/0xc0 [nfsv4] [<ffffffffa01549b7>] ? get_nfs_version+0x27/0x90 [nfs] [<ffffffffa0161a2d>] nfs_fs_mount+0x47d/0xd60 [nfs] [<ffffffff81a59c5e>] ? mutex_unlock+0xe/0x10 [<ffffffffa01606a0>] ? nfs_remount+0x430/0x430 [nfs] [<ffffffffa01609c0>] ? nfs_clone_super+0x140/0x140 [nfs] [<ffffffff81196489>] mount_fs+0x39/0x1b0 [<ffffffff81166145>] ? __alloc_percpu+0x15/0x20 [<ffffffff811b276b>] vfs_kern_mount+0x6b/0x150 [<ffffffff811b5830>] do_mount+0x210/0xbe0 [<ffffffff811b54ca>] ? copy_mount_options+0x3a/0x160 [<ffffffff811b651f>] SyS_mount+0x6f/0xb0 [<ffffffff81a5c852>] system_call_fastpath+0x12/0x17 Sleeping under the rcu_read_lock is bad. This patch fixes it by dropping the rcu_read_lock before doing the allocation and then reacquiring it and redoing the dereference before doing the copy. If we find that the string has somehow grown in the meantime, we'll reallocate and try again. Cc: <stable@vger.kernel.org> # v3.17+ Reported-by: "J. Bruce Fields" <bfields@fieldses.org> Signed-off-by: Jeff Layton <jlayton@primarydata.com> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Diffstat (limited to 'net/sunrpc/auth_gss')
-rw-r--r--net/sunrpc/auth_gss/auth_gss.c35
1 files changed, 30 insertions, 5 deletions
diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
index afb292cd797d..53ed8d3f8897 100644
--- a/net/sunrpc/auth_gss/auth_gss.c
+++ b/net/sunrpc/auth_gss/auth_gss.c
@@ -1353,6 +1353,7 @@ gss_stringify_acceptor(struct rpc_cred *cred)
char *string = NULL;
struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);
struct gss_cl_ctx *ctx;
+ unsigned int len;
struct xdr_netobj *acceptor;
rcu_read_lock();
@@ -1360,15 +1361,39 @@ gss_stringify_acceptor(struct rpc_cred *cred)
if (!ctx)
goto out;
- acceptor = &ctx->gc_acceptor;
+ len = ctx->gc_acceptor.len;
+ rcu_read_unlock();
/* no point if there's no string */
- if (!acceptor->len)
- goto out;
-
- string = kmalloc(acceptor->len + 1, GFP_KERNEL);
+ if (!len)
+ return NULL;
+realloc:
+ string = kmalloc(len + 1, GFP_KERNEL);
if (!string)
+ return NULL;
+
+ rcu_read_lock();
+ ctx = rcu_dereference(gss_cred->gc_ctx);
+
+ /* did the ctx disappear or was it replaced by one with no acceptor? */
+ if (!ctx || !ctx->gc_acceptor.len) {
+ kfree(string);
+ string = NULL;
goto out;
+ }
+
+ acceptor = &ctx->gc_acceptor;
+
+ /*
+ * Did we find a new acceptor that's longer than the original? Allocate
+ * a longer buffer and try again.
+ */
+ if (len < acceptor->len) {
+ len = acceptor->len;
+ rcu_read_unlock();
+ kfree(string);
+ goto realloc;
+ }
memcpy(string, acceptor->data, acceptor->len);
string[acceptor->len] = '\0';