We've been seeing some crashes in testing that look like this: BUG: unable to handle kernel NULL pointer dereference at (null) IP: [<ffffffff8135ce99>] memcpy_orig+0x29/0x110 PGD 212ca2067 PUD 212ca3067 PMD 0 Oops: 0002 [#1] SMP Modules linked in: rpcsec_gss_krb5 nfsv4 dns_resolver nfs fscache ppdev parport_pc i2c_piix4 sg parport i2c_core virtio_balloon pcspkr acpi_cpufreq nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables xfs libcrc32c sd_mod ata_generic pata_acpi virtio_scsi 8139too ata_piix libata 8139cp mii virtio_pci floppy virtio_ring serio_raw virtio CPU: 1 PID: 1540 Comm: nfsd Not tainted 4.9.0-rc1 #39 Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2007 task: ffff88020d7ed200 task.stack: ffff880211838000 RIP: 0010:[<ffffffff8135ce99>] [<ffffffff8135ce99>] memcpy_orig+0x29/0x110 RSP: 0018:ffff88021183bdd0 EFLAGS: 00010206 RAX: 0000000000000000 RBX: ffff88020d7fa000 RCX: 000000f400000000 RDX: 0000000000000014 RSI: ffff880212927020 RDI: 0000000000000000 RBP: ffff88021183be30 R08: 01000000ef896996 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff880211704ca8 R13: ffff88021473f000 R14: 00000000ef896996 R15: ffff880211704800 FS: 0000000000000000(0000) GS:ffff88021fc80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 0000000212ca1000 CR4: 00000000000006e0 Stack: ffffffffa01ea087 ffffffff63400001 ffff880215145e00 ffff880211bacd00 ffff88021473f2b8 0000000000000004 00000000d0679d67 ffff880211bacd00 ffff88020d7fa000 ffff88021473f000 0000000000000000 ffff88020d7faa30 Call Trace: [<ffffffffa01ea087>] ? svc_tcp_recvfrom+0x5a7/0x790 [sunrpc] [<ffffffffa01f84d8>] svc_recv+0xad8/0xbd0 [sunrpc] [<ffffffffa0262d5e>] nfsd+0xde/0x160 [nfsd] [<ffffffffa0262c80>] ? nfsd_destroy+0x60/0x60 [nfsd] [<ffffffff810a9418>] kthread+0xd8/0xf0 [<ffffffff816dbdbf>] ret_from_fork+0x1f/0x40 [<ffffffff810a9340>] ? kthread_park+0x60/0x60 Code: 00 00 48 89 f8 48 83 fa 20 72 7e 40 38 fe 7c 35 48 83 ea 20 48 83 ea 20 4c 8b 06 4c 8b 4e 08 4c 8b 56 10 4c 8b 5e 18 48 8d 76 20 <4c> 89 07 4c 89 4f 08 4c 89 57 10 4c 89 5f 18 48 8d 7f 20 73 d4 RIP [<ffffffff8135ce99>] memcpy_orig+0x29/0x110 RSP <ffff88021183bdd0> CR2: 0000000000000000 Both Bruce and Eryu ran a bisect here and found that the problematic patch was 68778945e46 (SUNRPC: Separate buffer pointers for RPC Call and Reply messages). That patch changed rpc_xdr_encode to use a new rq_rbuffer pointer to set up the receive buffer, but didn't change all of the necessary codepaths to set it properly. In particular the backchannel setup was missing. We need to set rq_rbuffer whenever rq_buffer is set. Ensure that it is. Cc: Chuck Lever <chuck.lever@xxxxxxxxxx> Reported-by: Eryu Guan <guaneryu@xxxxxxxxx> Reported-by: J. Bruce Fields <bfields@xxxxxxxxxxxx> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> --- net/sunrpc/xprtrdma/svc_rdma_backchannel.c | 1 + net/sunrpc/xprtsock.c | 1 + 2 files changed, 2 insertions(+) diff --git a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c index 2d8545c34095..fc4535ead7c2 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c +++ b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c @@ -182,6 +182,7 @@ xprt_rdma_bc_allocate(struct rpc_task *task) return -ENOMEM; rqst->rq_buffer = page_address(page); + rqst->rq_rbuffer = (char *)rqst->rq_buffer + rqst->rq_callsize; return 0; } diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c index 0137af1c0916..e01c825bc683 100644 --- a/net/sunrpc/xprtsock.c +++ b/net/sunrpc/xprtsock.c @@ -2563,6 +2563,7 @@ static int bc_malloc(struct rpc_task *task) buf->len = PAGE_SIZE; rqst->rq_buffer = buf->data; + rqst->rq_rbuffer = (char *)rqst->rq_buffer + rqst->rq_callsize; return 0; } -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
