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NFS: Fix rpcrdma_inline_fixup() crash with new LISTXATTRS operation 

By switching to an XFS-backed export, I am able to reproduce the
ibcomp worker crash on my client with xfstests generic/013.

For the failing LISTXATTRS operation, xdr_inline_pages() is called
with page_len=12 and buflen=128.

- When ->send_request() is called, rpcrdma_marshal_req() does not
  set up a Reply chunk because buflen is smaller than the inline
  threshold. Thus rpcrdma_convert_iovs() does not get invoked at
  all and the transport's XDRBUF_SPARSE_PAGES logic is not invoked
  on the receive buffer.

- During reply processing, rpcrdma_inline_fixup() tries to copy
  received data into rq_rcv_buf->pages because page_len is positive.
  But there are no receive pages because rpcrdma_marshal_req() never
  allocated them.

The result is that the ibcomp worker faults and dies. Sometimes that
causes a visible crash, and sometimes it results in a transport hang
without other symptoms.

RPC/RDMA's XDRBUF_SPARSE_PAGES support is not entirely correct, and
should eventually be fixed or replaced. However, my preference is
that upper-layer operations should explicitly allocate their receive
buffers (using GFP_KERNEL) when possible, rather than relying on
XDRBUF_SPARSE_PAGES.

Reported-by: Olga kornievskaia <kolga@netapp.com>
Suggested-by: Olga kornievskaia <kolga@netapp.com>
Fixes: c10a75145f ("NFSv4.2: add the extended attribute proc functions.")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Olga kornievskaia <kolga@netapp.com>
Reviewed-by: Frank van der Linden <fllinden@amazon.com>
Tested-by: Olga kornievskaia <kolga@netapp.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Chuck Lever 2020-11-24 19:15:18 -05:00 committed by Anna Schumaker
parent 0359af7ac3
commit 5482e09a88
2 changed files with 13 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
fs/nfs/nfs42proc.c
View File

@ -1241,12 +1241,13 @@ static ssize_t _nfs42_proc_listxattrs(struct inode *inode, void *buf,
.rpc_resp = &res,
};
u32 xdrlen;
int ret, np;
int ret, np, i;
ret = -ENOMEM;
res.scratch = alloc_page(GFP_KERNEL);
if (!res.scratch)
return -ENOMEM;
goto out;
xdrlen = nfs42_listxattr_xdrsize(buflen);
if (xdrlen > server->lxasize)
@ -1254,9 +1255,12 @@ static ssize_t _nfs42_proc_listxattrs(struct inode *inode, void *buf,
np = xdrlen / PAGE_SIZE + 1;
pages = kcalloc(np, sizeof(struct page *), GFP_KERNEL);
if (pages == NULL) {
__free_page(res.scratch);
return -ENOMEM;
if (!pages)
goto out_free_scratch;
for (i = 0; i < np; i++) {
pages[i] = alloc_page(GFP_KERNEL);
if (!pages[i])
goto out_free_pages;
}
arg.xattr_pages = pages;
@ -1271,14 +1275,15 @@ static ssize_t _nfs42_proc_listxattrs(struct inode *inode, void *buf,
*eofp = res.eof;
}
out_free_pages:
while (--np >= 0) {
if (pages[np])
__free_page(pages[np]);
}
__free_page(res.scratch);
kfree(pages);
out_free_scratch:
__free_page(res.scratch);
out:
return ret;
}

1
fs/nfs/nfs42xdr.c
View File

@ -1528,7 +1528,6 @@ static void nfs4_xdr_enc_listxattrs(struct rpc_rqst *req,
rpc_prepare_reply_pages(req, args->xattr_pages, 0, args->count,
hdr.replen);
req->rq_rcv_buf.flags |= XDRBUF_SPARSE_PAGES;
encode_nops(&hdr);
}