NFS: decode_dirent should use an xdr_stream

Convert nfs*xdr.c to use an xdr stream in decode_dirent.  This will prevent a
kernel oops that has been occuring when reading a vmapped page.

Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

6 files changed, 201 insertions, 39 deletions

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index fd30f185ec01..88cbcda76856 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -171,7 +171,7 @@ struct nfs_cache_array {
 
 #define MAX_READDIR_ARRAY ((PAGE_SIZE - sizeof(struct nfs_cache_array)) / sizeof(struct nfs_cache_array_entry))
 
-typedef __be32 * (*decode_dirent_t)(__be32 *, struct nfs_entry *, int);
+typedef __be32 * (*decode_dirent_t)(struct xdr_stream *, struct nfs_entry *, int);
 typedef struct {
         struct file     *file;
         struct page     *page;
@@ -357,13 +357,11 @@ error:
 
 /* Fill in an entry based on the xdr code stored in desc->page */
 static
-int xdr_decode(nfs_readdir_descriptor_t *desc, struct nfs_entry *entry, __be32 **ptr)
+int xdr_decode(nfs_readdir_descriptor_t *desc, struct nfs_entry *entry, struct xdr_stream *stream)
 {
-        __be32  *p = *ptr;
-        p = desc->decode(p, entry, desc->plus);
+        __be32 *p = desc->decode(stream, entry, desc->plus);
         if (IS_ERR(p))
                 return PTR_ERR(p);
-        *ptr = p;
 
         entry->fattr->time_start = desc->timestamp;
         entry->fattr->gencount = desc->gencount;
@@ -438,10 +436,23 @@ out:
 /* Perform conversion from xdr to cache array */
 static
 void nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc, struct nfs_entry *entry,
-                                struct page *xdr_page, struct page *page)
+                                struct page *xdr_page, struct page *page, unsigned int buflen)
 {
+        struct xdr_stream stream;
+        struct xdr_buf buf;
         __be32 *ptr = kmap(xdr_page);
-        while (xdr_decode(desc, entry, &ptr) == 0) {
+
+        buf.head->iov_base = xdr_page;
+        buf.head->iov_len = buflen;
+        buf.tail->iov_len = 0;
+        buf.page_base = 0;
+        buf.page_len = 0;
+        buf.buflen = buf.head->iov_len;
+        buf.len = buf.head->iov_len;
+
+        xdr_init_decode(&stream, &buf, ptr);
+
+        while (xdr_decode(desc, entry, &stream) == 0) {
                 if (nfs_readdir_add_to_array(entry, page) == -1)
                         break;
                 if (desc->plus == 1)
@@ -458,6 +469,7 @@ int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page *page,
         struct file     *file = desc->file;
         struct nfs_cache_array *array;
         int status = 0;
+        unsigned int array_size = 1;
 
         entry.prev_cookie = 0;
         entry.cookie = *desc->dir_cookie;
@@ -476,9 +488,10 @@ int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page *page,
                 goto out_release_array;
         do {
                 status = nfs_readdir_xdr_filler(xdr_page, desc, &entry, file, inode);
+
                 if (status < 0)
                         break;
-                nfs_readdir_page_filler(desc, &entry, xdr_page, page);
+                nfs_readdir_page_filler(desc, &entry, xdr_page, page, array_size * PAGE_SIZE);
         } while (array->eof_index < 0 && array->size < MAX_READDIR_ARRAY);
 
         put_page(xdr_page);
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index c961bc92c107..74b015598a43 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -181,15 +181,15 @@ extern void nfs_destroy_directcache(void);
 /* nfs2xdr.c */
 extern int nfs_stat_to_errno(int);
 extern struct rpc_procinfo nfs_procedures[];
-extern __be32 * nfs_decode_dirent(__be32 *, struct nfs_entry *, int);
+extern __be32 *nfs_decode_dirent(struct xdr_stream *, struct nfs_entry *, int);
 
 /* nfs3xdr.c */
 extern struct rpc_procinfo nfs3_procedures[];
-extern __be32 *nfs3_decode_dirent(__be32 *, struct nfs_entry *, int);
+extern __be32 *nfs3_decode_dirent(struct xdr_stream *, struct nfs_entry *, int);
 
 /* nfs4xdr.c */
 #ifdef CONFIG_NFS_V4
-extern __be32 *nfs4_decode_dirent(__be32 *p, struct nfs_entry *entry, int plus);
+extern __be32 *nfs4_decode_dirent(struct xdr_stream *, struct nfs_entry *entry, int plus);
 #endif
 #ifdef CONFIG_NFS_V4_1
 extern const u32 nfs41_maxread_overhead;
diff --git a/fs/nfs/nfs2xdr.c b/fs/nfs/nfs2xdr.c
index 79c74387a2fe..0210c752e743 100644
--- a/fs/nfs/nfs2xdr.c
+++ b/fs/nfs/nfs2xdr.c
@@ -500,25 +500,56 @@ err_unmap:
         goto out;
 }
 
+static void print_overflow_msg(const char *func, const struct xdr_stream *xdr)
+{
+        dprintk("nfs: %s: prematurely hit end of receive buffer. "
+                "Remaining buffer length is %tu words.\n",
+                func, xdr->end - xdr->p);
+}
+
 __be32 *
-nfs_decode_dirent(__be32 *p, struct nfs_entry *entry, int plus)
+nfs_decode_dirent(struct xdr_stream *xdr, struct nfs_entry *entry, int plus)
 {
-        if (!*p++) {
-                if (!*p)
+        __be32 *p;
+        p = xdr_inline_decode(xdr, 4);
+        if (unlikely(!p))
+                goto out_overflow;
+        if (!ntohl(*p++)) {
+                p = xdr_inline_decode(xdr, 4);
+                if (unlikely(!p))
+                        goto out_overflow;
+                if (!ntohl(*p++))
                         return ERR_PTR(-EAGAIN);
                 entry->eof = 1;
                 return ERR_PTR(-EBADCOOKIE);
         }
 
+        p = xdr_inline_decode(xdr, 8);
+        if (unlikely(!p))
+                goto out_overflow;
+
         entry->ino        = ntohl(*p++);
         entry->len        = ntohl(*p++);
+
+        p = xdr_inline_decode(xdr, entry->len + 4);
+        if (unlikely(!p))
+                goto out_overflow;
         entry->name       = (const char *) p;
         p                += XDR_QUADLEN(entry->len);
         entry->prev_cookie        = entry->cookie;
         entry->cookie     = ntohl(*p++);
-        entry->eof        = !p[0] && p[1];
+
+        p = xdr_inline_peek(xdr, 8);
+        if (p != NULL)
+                entry->eof = !p[0] && p[1];
+        else
+                entry->eof = 0;
 
         return p;
+
+out_overflow:
+        print_overflow_msg(__func__, xdr);
+        return ERR_PTR(-EIO);
 }
 
 /*
diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
index 52b2fda66e63..d562c8d9d56e 100644
--- a/fs/nfs/nfs3xdr.c
+++ b/fs/nfs/nfs3xdr.c
@@ -100,6 +100,13 @@ static const umode_t nfs_type2fmt[] = {
         [NF3FIFO] = S_IFIFO,
 };
 
+static void print_overflow_msg(const char *func, const struct xdr_stream *xdr)
+{
+        dprintk("nfs: %s: prematurely hit end of receive buffer. "
+                "Remaining buffer length is %tu words.\n",
+                func, xdr->end - xdr->p);
+}
+
 /*
  * Common NFS XDR functions as inlines
  */
@@ -119,6 +126,29 @@ xdr_decode_fhandle(__be32 *p, struct nfs_fh *fh)
         return NULL;
 }
 
+static inline __be32 *
+xdr_decode_fhandle_stream(struct xdr_stream *xdr, struct nfs_fh *fh)
+{
+        __be32 *p;
+        p = xdr_inline_decode(xdr, 4);
+        if (unlikely(!p))
+                goto out_overflow;
+        fh->size = ntohl(*p++);
+
+        if (fh->size <= NFS3_FHSIZE) {
+                p = xdr_inline_decode(xdr, fh->size);
+                if (unlikely(!p))
+                        goto out_overflow;
+                memcpy(fh->data, p, fh->size);
+                return p + XDR_QUADLEN(fh->size);
+        }
+        return NULL;
+
+out_overflow:
+        print_overflow_msg(__func__, xdr);
+        return ERR_PTR(-EIO);
+}
+
 /*
  * Encode/decode time.
  */
@@ -241,6 +271,26 @@ xdr_decode_post_op_attr(__be32 *p, struct nfs_fattr *fattr)
 }
 
 static inline __be32 *
+xdr_decode_post_op_attr_stream(struct xdr_stream *xdr, struct nfs_fattr *fattr)
+{
+        __be32 *p;
+
+        p = xdr_inline_decode(xdr, 4);
+        if (unlikely(!p))
+                goto out_overflow;
+        if (ntohl(*p++)) {
+                p = xdr_inline_decode(xdr, 84);
+                if (unlikely(!p))
+                        goto out_overflow;
+                p = xdr_decode_fattr(p, fattr);
+        }
+        return p;
+out_overflow:
+        print_overflow_msg(__func__, xdr);
+        return ERR_PTR(-EIO);
+}
+
+static inline __be32 *
 xdr_decode_pre_op_attr(__be32 *p, struct nfs_fattr *fattr)
 {
         if (*p++)
@@ -616,19 +666,33 @@ err_unmap:
 }
 
 __be32 *
-nfs3_decode_dirent(__be32 *p, struct nfs_entry *entry, int plus)
+nfs3_decode_dirent(struct xdr_stream *xdr, struct nfs_entry *entry, int plus)
 {
+        __be32 *p;
         struct nfs_entry old = *entry;
 
-        if (!*p++) {
-                if (!*p)
+        p = xdr_inline_decode(xdr, 4);
+        if (unlikely(!p))
+                goto out_overflow;
+        if (!ntohl(*p++)) {
+                p = xdr_inline_decode(xdr, 4);
+                if (unlikely(!p))
+                        goto out_overflow;
+                if (!ntohl(*p++))
                         return ERR_PTR(-EAGAIN);
                 entry->eof = 1;
                 return ERR_PTR(-EBADCOOKIE);
         }
 
+        p = xdr_inline_decode(xdr, 12);
+        if (unlikely(!p))
+                goto out_overflow;
         p = xdr_decode_hyper(p, &entry->ino);
         entry->len  = ntohl(*p++);
+
+        p = xdr_inline_decode(xdr, entry->len + 8);
+        if (unlikely(!p))
+                goto out_overflow;
         entry->name = (const char *) p;
         p += XDR_QUADLEN(entry->len);
         entry->prev_cookie = entry->cookie;
@@ -636,10 +700,17 @@ nfs3_decode_dirent(__be32 *p, struct nfs_entry *entry, int plus)
 
         if (plus) {
                 entry->fattr->valid = 0;
-                p = xdr_decode_post_op_attr(p, entry->fattr);
+                p = xdr_decode_post_op_attr_stream(xdr, entry->fattr);
+                if (IS_ERR(p))
+                        goto out_overflow_exit;
                 /* In fact, a post_op_fh3: */
+                p = xdr_inline_decode(xdr, 4);
+                if (unlikely(!p))
+                        goto out_overflow;
                 if (*p++) {
-                        p = xdr_decode_fhandle(p, entry->fh);
+                        p = xdr_decode_fhandle_stream(xdr, entry->fh);
+                        if (IS_ERR(p))
+                                goto out_overflow_exit;
                         /* Ugh -- server reply was truncated */
                         if (p == NULL) {
                                 dprintk("NFS: FH truncated\n");
@@ -650,8 +721,18 @@ nfs3_decode_dirent(__be32 *p, struct nfs_entry *entry, int plus)
                         memset((u8*)(entry->fh), 0, sizeof(*entry->fh));
         }
 
-        entry->eof = !p[0] && p[1];
+        p = xdr_inline_peek(xdr, 8);
+        if (p != NULL)
+                entry->eof = !p[0] && p[1];
+        else
+                entry->eof = 0;
+
         return p;
+
+out_overflow:
+        print_overflow_msg(__func__, xdr);
+out_overflow_exit:
+        return ERR_PTR(-EIO);
 }
 
 /*
diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index d24a8e07b5e2..c58ea6377506 100644
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -331,7 +331,7 @@ extern void nfs_free_seqid(struct nfs_seqid *seqid);
 extern const nfs4_stateid zero_stateid;
 
 /* nfs4xdr.c */
-extern __be32 *nfs4_decode_dirent(__be32 *p, struct nfs_entry *entry, int plus);
+extern __be32 *nfs4_decode_dirent(struct xdr_stream *, struct nfs_entry *entry, int plus);
 extern struct rpc_procinfo nfs4_procedures[];
 
 struct nfs4_mount_data;
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 6ea5c9392fe4..a4919e999354 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -3950,13 +3950,13 @@ static int decode_lock_denied (struct xdr_stream *xdr, struct file_lock *fl)
         __be32 *p;
         uint32_t namelen, type;
 
-        p = xdr_inline_decode(xdr, 32);
+        p = xdr_inline_decode(xdr, 32); /* read 32 bytes */
         if (unlikely(!p))
                 goto out_overflow;
-        p = xdr_decode_hyper(p, &offset);
+        p = xdr_decode_hyper(p, &offset); /* read 2 8-byte long words */
         p = xdr_decode_hyper(p, &length);
-        type = be32_to_cpup(p++);
-        if (fl != NULL) {
+        type = be32_to_cpup(p++); /* 4 byte read */
+        if (fl != NULL) { /* manipulate file lock */
                 fl->fl_start = (loff_t)offset;
                 fl->fl_end = fl->fl_start + (loff_t)length - 1;
                 if (length == ~(uint64_t)0)
@@ -3966,9 +3966,9 @@ static int decode_lock_denied (struct xdr_stream *xdr, struct file_lock *fl)
                         fl->fl_type = F_RDLCK;
                 fl->fl_pid = 0;
         }
-        p = xdr_decode_hyper(p, &clientid);
-        namelen = be32_to_cpup(p);
-        p = xdr_inline_decode(xdr, namelen);
+        p = xdr_decode_hyper(p, &clientid); /* read 8 bytes */
+        namelen = be32_to_cpup(p); /* read 4 bytes */  /* have read all 32 bytes now */
+        p = xdr_inline_decode(xdr, namelen); /* variable size field */
         if (likely(p))
                 return -NFS4ERR_DENIED;
 out_overflow:
@@ -5755,21 +5755,33 @@ static int nfs4_xdr_dec_reclaim_complete(struct rpc_rqst *rqstp, uint32_t *p,
 }
 #endif /* CONFIG_NFS_V4_1 */
 
-__be32 *nfs4_decode_dirent(__be32 *p, struct nfs_entry *entry, int plus)
+__be32 *nfs4_decode_dirent(struct xdr_stream *xdr, struct nfs_entry *entry, int plus)
 {
         uint32_t bitmap[2] = {0};
         uint32_t len;
-
-        if (!*p++) {
-                if (!*p)
+        __be32 *p = xdr_inline_decode(xdr, 4);
+        if (unlikely(!p))
+                goto out_overflow;
+        if (!ntohl(*p++)) {
+                p = xdr_inline_decode(xdr, 4);
+                if (unlikely(!p))
+                        goto out_overflow;
+                if (!ntohl(*p++))
                         return ERR_PTR(-EAGAIN);
                 entry->eof = 1;
                 return ERR_PTR(-EBADCOOKIE);
         }
 
+        p = xdr_inline_decode(xdr, 12);
+        if (unlikely(!p))
+                goto out_overflow;
         entry->prev_cookie = entry->cookie;
         p = xdr_decode_hyper(p, &entry->cookie);
         entry->len = ntohl(*p++);
+
+        p = xdr_inline_decode(xdr, entry->len + 4);
+        if (unlikely(!p))
+                goto out_overflow;
         entry->name = (const char *) p;
         p += XDR_QUADLEN(entry->len);
 
@@ -5782,29 +5794,54 @@ __be32 *nfs4_decode_dirent(__be32 *p, struct nfs_entry *entry, int plus)
 
         len = ntohl(*p++);              /* bitmap length */
         if (len-- > 0) {
+                p = xdr_inline_decode(xdr, 4);
+                if (unlikely(!p))
+                        goto out_overflow;
                 bitmap[0] = ntohl(*p++);
                 if (len-- > 0) {
+                        p = xdr_inline_decode(xdr, 4);
+                        if (unlikely(!p))
+                                goto out_overflow;
                         bitmap[1] = ntohl(*p++);
                         p += len;
                 }
         }
+        p = xdr_inline_decode(xdr, 4);
+        if (unlikely(!p))
+                goto out_overflow;
         len = XDR_QUADLEN(ntohl(*p++)); /* attribute buffer length */
         if (len > 0) {
                 if (bitmap[0] & FATTR4_WORD0_RDATTR_ERROR) {
                         bitmap[0] &= ~FATTR4_WORD0_RDATTR_ERROR;
                         /* Ignore the return value of rdattr_error for now */
-                        p++;
-                        len--;
+                        p = xdr_inline_decode(xdr, 4);
+                        if (unlikely(!p))
+                                goto out_overflow;
                 }
-                if (bitmap[0] == 0 && bitmap[1] == FATTR4_WORD1_MOUNTED_ON_FILEID)
+                if (bitmap[0] == 0 && bitmap[1] == FATTR4_WORD1_MOUNTED_ON_FILEID) {
+                        p = xdr_inline_decode(xdr, 8);
+                        if (unlikely(!p))
+                                goto out_overflow;
                         xdr_decode_hyper(p, &entry->ino);
-                else if (bitmap[0] == FATTR4_WORD0_FILEID)
+                } else if (bitmap[0] == FATTR4_WORD0_FILEID) {
+                        p = xdr_inline_decode(xdr, 8);
+                        if (unlikely(!p))
+                                goto out_overflow;
                         xdr_decode_hyper(p, &entry->ino);
-                p += len;
+                }
         }
 
-        entry->eof = !p[0] && p[1];
+        p = xdr_inline_peek(xdr, 8);
+        if (p != NULL)
+                entry->eof = !p[0] && p[1];
+        else
+                entry->eof = 0;
+
         return p;
+
+out_overflow:
+        print_overflow_msg(__func__, xdr);
+        return ERR_PTR(-EIO);
 }
 
 /*