From: Stefan Hajnoczi <stefanha@redhat.com>

Date: Mon, 27 Jan 2020 19:01:21 +0000

Subject: [PATCH] virtiofsd: add fuse_mbuf_iter API

Introduce an API for consuming bytes from a buffer with size checks.

All FUSE operations will be converted to use this safe API instead of

void *inarg.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

(cherry picked from commit dad157e880416ab3a0e45beaa0e81977516568bc)

---

 tools/virtiofsd/buffer.c      | 28 ++++++++++++++++++++

 tools/virtiofsd/fuse_common.h | 49 ++++++++++++++++++++++++++++++++++-

 2 files changed, 76 insertions(+), 1 deletion(-)

diff --git a/tools/virtiofsd/buffer.c b/tools/virtiofsd/buffer.c

index 772efa922d..42a608f6bd 100644

--- a/tools/virtiofsd/buffer.c

+++ b/tools/virtiofsd/buffer.c

@@ -267,3 +267,31 @@ ssize_t fuse_buf_copy(struct fuse_bufvec *dstv, struct fuse_bufvec *srcv)

     return copied;

 }

+

+void *fuse_mbuf_iter_advance(struct fuse_mbuf_iter *iter, size_t len)

+{

+    void *ptr;

+

+    if (len > iter->size - iter->pos) {

+        return NULL;

+    }

+

+    ptr = iter->mem + iter->pos;

+    iter->pos += len;

+    return ptr;

+}

+

+const char *fuse_mbuf_iter_advance_str(struct fuse_mbuf_iter *iter)

+{

+    const char *str = iter->mem + iter->pos;

+    size_t remaining = iter->size - iter->pos;

+    size_t i;

+

+    for (i = 0; i < remaining; i++) {

+        if (str[i] == '\0') {

+            iter->pos += i + 1;

+            return str;

+        }

+    }

+    return NULL;

+}

diff --git a/tools/virtiofsd/fuse_common.h b/tools/virtiofsd/fuse_common.h

index 0cb33acc2f..f8f6433743 100644

--- a/tools/virtiofsd/fuse_common.h

+++ b/tools/virtiofsd/fuse_common.h

@@ -703,10 +703,57 @@ size_t fuse_buf_size(const struct fuse_bufvec *bufv);

  */

 ssize_t fuse_buf_copy(struct fuse_bufvec *dst, struct fuse_bufvec *src);

+/**

+ * Memory buffer iterator

+ *

+ */

+struct fuse_mbuf_iter {

+    /**

+     * Data pointer

+     */

+    void *mem;

+

+    /**

+     * Total length, in bytes

+     */

+    size_t size;

+

+    /**

+     * Offset from start of buffer

+     */

+    size_t pos;

+};

+

+/* Initialize memory buffer iterator from a fuse_buf */

+#define FUSE_MBUF_ITER_INIT(fbuf) \

+    ((struct fuse_mbuf_iter){     \

+        .mem = fbuf->mem,         \

+        .size = fbuf->size,       \

+        .pos = 0,                 \

+    })

+

+/**

+ * Consume bytes from a memory buffer iterator

+ *

+ * @param iter memory buffer iterator

+ * @param len number of bytes to consume

+ * @return pointer to start of consumed bytes or

+ *         NULL if advancing beyond end of buffer

+ */

+void *fuse_mbuf_iter_advance(struct fuse_mbuf_iter *iter, size_t len);

+

+/**

+ * Consume a NUL-terminated string from a memory buffer iterator

+ *

+ * @param iter memory buffer iterator

+ * @return pointer to the string or

+ *         NULL if advancing beyond end of buffer or there is no NUL-terminator

+ */

+const char *fuse_mbuf_iter_advance_str(struct fuse_mbuf_iter *iter);

+

 /*

  * Signal handling

  */

-

 /**

  * Exit session on HUP, TERM and INT signals and ignore PIPE signal

  *