NFSv4: include bitmap in nfsv4 get acl data

The NFSv4 bitmap size is unbounded: a server can return an arbitrary
sized bitmap in an FATTR4_WORD0_ACL request.  Replace using the
nfs4_fattr_bitmap_maxsz as a guess to the maximum bitmask returned by a server
with the inclusion of the bitmap (xdr length plus bitmasks) and the acl data
xdr length to the (cached) acl page data.

This is a general solution to commit e5012d1f "NFSv4.1: update
nfs4_fattr_bitmap_maxsz" and fixes hitting a BUG_ON in xdr_shrink_bufhead
when getting ACLs.

Fix a bug in decode_getacl that returned -EINVAL on ACLs > page when getxattr
was called with a NULL buffer, preventing ACL > PAGE_SIZE from being retrieved.

Cc: stable@kernel.org
Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index fcc2408..3b10801 100644 (file)
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -3426,19 +3426,6 @@ static inline int nfs4_server_supports_acls(struct nfs_server *server)
  */
 #define NFS4ACL_MAXPAGES (XATTR_SIZE_MAX >> PAGE_CACHE_SHIFT)
 
-static void buf_to_pages(const void *buf, size_t buflen,
-               struct page **pages, unsigned int *pgbase)
-{
-       const void *p = buf;
-
-       *pgbase = offset_in_page(buf);
-       p -= *pgbase;
-       while (p < buf + buflen) {
-               *(pages++) = virt_to_page(p);
-               p += PAGE_CACHE_SIZE;
-       }
-}
-
 static int buf_to_pages_noslab(const void *buf, size_t buflen,
                struct page **pages, unsigned int *pgbase)
 {
@@ -3535,9 +3522,19 @@ out:
        nfs4_set_cached_acl(inode, acl);
 }
 
+/*
+ * The getxattr API returns the required buffer length when called with a
+ * NULL buf. The NFSv4 acl tool then calls getxattr again after allocating
+ * the required buf.  On a NULL buf, we send a page of data to the server
+ * guessing that the ACL request can be serviced by a page. If so, we cache
+ * up to the page of ACL data, and the 2nd call to getxattr is serviced by
+ * the cache. If not so, we throw away the page, and cache the required
+ * length. The next getxattr call will then produce another round trip to
+ * the server, this time with the input buf of the required size.
+ */
 static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t buflen)
 {
-       struct page *pages[NFS4ACL_MAXPAGES];
+       struct page *pages[NFS4ACL_MAXPAGES] = {NULL, };
        struct nfs_getaclargs args = {
                .fh = NFS_FH(inode),
                .acl_pages = pages,
@@ -3552,41 +3549,60 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
                .rpc_argp = &args,
                .rpc_resp = &res,
        };
-       struct page *localpage = NULL;
-       int ret;
+       int ret = -ENOMEM, npages, i, acl_len = 0;
 
-       if (buflen < PAGE_SIZE) {
-               /* As long as we're doing a round trip to the server anyway,
-                * let's be prepared for a page of acl data. */
-               localpage = alloc_page(GFP_KERNEL);
-               resp_buf = page_address(localpage);
-               if (localpage == NULL)
-                       return -ENOMEM;
-               args.acl_pages[0] = localpage;
-               args.acl_pgbase = 0;
-               args.acl_len = PAGE_SIZE;
-       } else {
-               resp_buf = buf;
-               buf_to_pages(buf, buflen, args.acl_pages, &args.acl_pgbase);
+       npages = (buflen + PAGE_SIZE - 1) >> PAGE_SHIFT;
+       /* As long as we're doing a round trip to the server anyway,
+        * let's be prepared for a page of acl data. */
+       if (npages == 0)
+               npages = 1;
+
+       for (i = 0; i < npages; i++) {
+               pages[i] = alloc_page(GFP_KERNEL);
+               if (!pages[i])
+                       goto out_free;
+       }
+       if (npages > 1) {
+               /* for decoding across pages */
+               args.acl_scratch = alloc_page(GFP_KERNEL);
+               if (!args.acl_scratch)
+                       goto out_free;
        }
-       ret = nfs4_call_sync(NFS_SERVER(inode)->client, NFS_SERVER(inode), &msg, &args.seq_args, &res.seq_res, 0);
+       args.acl_len = npages * PAGE_SIZE;
+       args.acl_pgbase = 0;
+       /* Let decode_getfacl know not to fail if the ACL data is larger than
+        * the page we send as a guess */
+       if (buf == NULL)
+               res.acl_flags |= NFS4_ACL_LEN_REQUEST;
+       resp_buf = page_address(pages[0]);
+
+       dprintk("%s  buf %p buflen %ld npages %d args.acl_len %ld\n",
+               __func__, buf, buflen, npages, args.acl_len);
+       ret = nfs4_call_sync(NFS_SERVER(inode)->client, NFS_SERVER(inode),
+                            &msg, &args.seq_args, &res.seq_res, 0);
        if (ret)
                goto out_free;
-       if (res.acl_len > args.acl_len)
-               nfs4_write_cached_acl(inode, NULL, res.acl_len);
+
+       acl_len = res.acl_len - res.acl_data_offset;
+       if (acl_len > args.acl_len)
+               nfs4_write_cached_acl(inode, NULL, acl_len);
        else
-               nfs4_write_cached_acl(inode, resp_buf, res.acl_len);
+               nfs4_write_cached_acl(inode, resp_buf + res.acl_data_offset,
+                                     acl_len);
        if (buf) {
                ret = -ERANGE;
-               if (res.acl_len > buflen)
+               if (acl_len > buflen)
                        goto out_free;
-               if (localpage)
-                       memcpy(buf, resp_buf, res.acl_len);
+               _copy_from_pages(buf, pages, res.acl_data_offset,
+                               res.acl_len);
        }
-       ret = res.acl_len;
+       ret = acl_len;
 out_free:
-       if (localpage)
-               __free_page(localpage);
+       for (i = 0; i < npages; i++)
+               if (pages[i])
+                       __free_page(pages[i]);
+       if (args.acl_scratch)
+               __free_page(args.acl_scratch);
        return ret;
 }
 
@@ -3617,6 +3633,8 @@ static ssize_t nfs4_proc_get_acl(struct inode *inode, void *buf, size_t buflen)
                nfs_zap_acl_cache(inode);
        ret = nfs4_read_cached_acl(inode, buf, buflen);
        if (ret != -ENOENT)
+               /* -ENOENT is returned if there is no ACL or if there is an ACL
+                * but no cached acl data, just the acl length */
                return ret;
        return nfs4_get_acl_uncached(inode, buf, buflen);
 }

diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index e6161b2..dcaf693 100644 (file)
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -2517,11 +2517,13 @@ static void nfs4_xdr_enc_getacl(struct rpc_rqst *req, struct xdr_stream *xdr,
        encode_compound_hdr(xdr, req, &hdr);
        encode_sequence(xdr, &args->seq_args, &hdr);
        encode_putfh(xdr, args->fh, &hdr);
-       replen = hdr.replen + op_decode_hdr_maxsz + nfs4_fattr_bitmap_maxsz + 1;
+       replen = hdr.replen + op_decode_hdr_maxsz + 1;
        encode_getattr_two(xdr, FATTR4_WORD0_ACL, 0, &hdr);
 
        xdr_inline_pages(&req->rq_rcv_buf, replen << 2,
                args->acl_pages, args->acl_pgbase, args->acl_len);
+       xdr_set_scratch_buffer(xdr, page_address(args->acl_scratch), PAGE_SIZE);
+
        encode_nops(&hdr);
 }
 
@@ -4957,17 +4959,18 @@ decode_restorefh(struct xdr_stream *xdr)
 }
 
 static int decode_getacl(struct xdr_stream *xdr, struct rpc_rqst *req,
-               size_t *acl_len)
+                        struct nfs_getaclres *res)
 {
-       __be32 *savep;
+       __be32 *savep, *bm_p;
        uint32_t attrlen,
                 bitmap[3] = {0};
        struct kvec *iov = req->rq_rcv_buf.head;
        int status;
 
-       *acl_len = 0;
+       res->acl_len = 0;
        if ((status = decode_op_hdr(xdr, OP_GETATTR)) != 0)
                goto out;
+       bm_p = xdr->p;
        if ((status = decode_attr_bitmap(xdr, bitmap)) != 0)
                goto out;
        if ((status = decode_attr_length(xdr, &attrlen, &savep)) != 0)
@@ -4979,18 +4982,30 @@ static int decode_getacl(struct xdr_stream *xdr, struct rpc_rqst *req,
                size_t hdrlen;
                u32 recvd;
 
+               /* The bitmap (xdr len + bitmaps) and the attr xdr len words
+                * are stored with the acl data to handle the problem of
+                * variable length bitmaps.*/
+               xdr->p = bm_p;
+               res->acl_data_offset = be32_to_cpup(bm_p) + 2;
+               res->acl_data_offset <<= 2;
+
                /* We ignore &savep and don't do consistency checks on
                 * the attr length.  Let userspace figure it out.... */
                hdrlen = (u8 *)xdr->p - (u8 *)iov->iov_base;
+               attrlen += res->acl_data_offset;
                recvd = req->rq_rcv_buf.len - hdrlen;
                if (attrlen > recvd) {
-                       dprintk("NFS: server cheating in getattr"
-                                       " acl reply: attrlen %u > recvd %u\n",
+                       if (res->acl_flags & NFS4_ACL_LEN_REQUEST) {
+                               /* getxattr interface called with a NULL buf */
+                               res->acl_len = attrlen;
+                               goto out;
+                       }
+                       dprintk("NFS: acl reply: attrlen %u > recvd %u\n",
                                        attrlen, recvd);
                        return -EINVAL;
                }
                xdr_read_pages(xdr, attrlen);
-               *acl_len = attrlen;
+               res->acl_len = attrlen;
        } else
                status = -EOPNOTSUPP;
 
@@ -6028,7 +6043,7 @@ nfs4_xdr_dec_getacl(struct rpc_rqst *rqstp, struct xdr_stream *xdr,
        status = decode_putfh(xdr);
        if (status)
                goto out;
-       status = decode_getacl(xdr, rqstp, &res->acl_len);
+       status = decode_getacl(xdr, rqstp, res);
 
 out:
        return status;

diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index 2a7c533..6c898af 100644 (file)
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -602,11 +602,16 @@ struct nfs_getaclargs {
        size_t                          acl_len;
        unsigned int                    acl_pgbase;
        struct page **                  acl_pages;
+       struct page *                   acl_scratch;
        struct nfs4_sequence_args       seq_args;
 };
 
+/* getxattr ACL interface flags */
+#define NFS4_ACL_LEN_REQUEST   0x0001  /* zero length getxattr buffer */
 struct nfs_getaclres {
        size_t                          acl_len;
+       size_t                          acl_data_offset;
+       int                             acl_flags;
        struct nfs4_sequence_res        seq_res;
 };
 

diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h
index a20970e..af70af3 100644 (file)
--- a/include/linux/sunrpc/xdr.h
+++ b/include/linux/sunrpc/xdr.h
@@ -191,6 +191,8 @@ extern int xdr_decode_array2(struct xdr_buf *buf, unsigned int base,
                             struct xdr_array2_desc *desc);
 extern int xdr_encode_array2(struct xdr_buf *buf, unsigned int base,
                             struct xdr_array2_desc *desc);
+extern void _copy_from_pages(char *p, struct page **pages, size_t pgbase,
+                            size_t len);
 
 /*
  * Provide some simple tools for XDR buffer overflow-checking etc.

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 277ebd4..593f4c6 100644 (file)
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -296,7 +296,7 @@ _copy_to_pages(struct page **pages, size_t pgbase, const char *p, size_t len)
  * Copies data into an arbitrary memory location from an array of pages
  * The copy is assumed to be non-overlapping.
  */
-static void
+void
 _copy_from_pages(char *p, struct page **pages, size_t pgbase, size_t len)
 {
        struct page **pgfrom;
@@ -324,6 +324,7 @@ _copy_from_pages(char *p, struct page **pages, size_t pgbase, size_t len)
 
        } while ((len -= copy) != 0);
 }
+EXPORT_SYMBOL_GPL(_copy_from_pages);
 
 /*
  * xdr_shrink_bufhead