This is a note to let you know that I've just added the patch titled
sunrpc: fix sleeping under rcu_read_lock in gss_stringify_acceptor
to the 3.17-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sunrpc-fix-sleeping-under-rcu_read_lock-in-gss_stringify_acceptor.patch
and it can be found in the queue-3.17 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b3ecba096729f521312d1863ad22530695527aed Mon Sep 17 00:00:00 2001
From: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
Date: Thu, 13 Nov 2014 07:30:46 -0500
Subject: sunrpc: fix sleeping under rcu_read_lock in gss_stringify_acceptor
From: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
commit b3ecba096729f521312d1863ad22530695527aed upstream.
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.
Reported-by: "J. Bruce Fields" <bfields@xxxxxxxxxxxx>
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/sunrpc/auth_gss/auth_gss.c | 35 ++++++++++++++++++++++++++++++-----
1 file changed, 30 insertions(+), 5 deletions(-)
--- 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 *
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 *
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';
Patches currently in stable-queue which might be from jlayton@xxxxxxxxxxxxxxx are
queue-3.17/sunrpc-fix-sleeping-under-rcu_read_lock-in-gss_stringify_acceptor.patch
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