HGFS: Fix a Linux client memory corruption

When doing partial page writes the Linux HGFS client would trash the
initial part of the page leading up to the start of the write and also
trash the remaining part of the page after the written segment of the
page.

This trashing of the initial part of the page was incorrect and
overwrites earlier partial page writes to that page.  This was also
incorrect as the arguments for the offsets into the page were
miscalculated.

Signed-off-by: Dmitry Torokhov <dtor@vmware.com>

diff --git a/open-vm-tools/modules/linux/vmhgfs/page.c b/open-vm-tools/modules/linux/vmhgfs/page.c
index 4aec48830c4b052bca9915033052206d16349488..5b68232697f7137ab0198f79191a1508ea91a2d9 100644 (file)
--- a/open-vm-tools/modules/linux/vmhgfs/page.c
+++ b/open-vm-tools/modules/linux/vmhgfs/page.c
@@ -472,6 +472,7 @@ HgfsDoWrite(HgfsHandle handle,             // IN: Handle for this file
       replyStatus = HgfsReplyStatus(req);
       result = HgfsStatusConvertToLinux(replyStatus);
 
+      LOG(4, (KERN_WARNING "VMware hgfs: HgfsDoWrite: res %u\n", result));
       switch (result) {
       case 0:
          if (opUsed == HGFS_OP_WRITE_V3 || opUsed == HGFS_OP_WRITE_FAST_V4) {
@@ -598,6 +599,8 @@ HgfsDoReadpage(HgfsHandle handle,  // IN:     Handle to use for reading
     */
    if (remainingCount) {
       char *buffer = kmap(page) + pageTo;
+      LOG(6, (KERN_DEBUG "VMware hgfs: %s: zeroing last %Zu bytes\n",
+              __func__, remainingCount));
       memset(buffer - remainingCount, 0, remainingCount);
       kunmap(page);
    }
@@ -815,6 +818,8 @@ HgfsWritepage(struct page *page,             // IN: Page to write from
     */
    currentFileSize = compat_i_size_read(inode);
    lastPageIndex = currentFileSize >> PAGE_CACHE_SHIFT;
+   LOG(4, (KERN_WARNING "VMware hgfs: %s: file size lpi %lu pi %lu\n",
+           __func__, lastPageIndex, page->index));
    if (page->index > lastPageIndex) {
       goto exit;
    } else if (page->index == lastPageIndex) {
@@ -902,9 +907,6 @@ HgfsDoWriteBegin(struct page *page,         // IN: Page to be written
        ((pageFrom == 0) && (offset + pageTo) >= currentFileSize)) {
       void *kaddr = compat_kmap_atomic(page);
 
-      if (pageFrom) {
-         memset(kaddr, 0, pageFrom);
-      }
       if (pageTo < PAGE_CACHE_SIZE) {
          memset(kaddr + pageTo, 0, PAGE_CACHE_SIZE - pageTo);
       }
@@ -977,8 +979,8 @@ HgfsWriteBegin(struct file *file,             // IN: File to be written
                void **clientData)             // OUT: Opaque to pass to write_end, unused
 {
    pgoff_t index = pos >> PAGE_CACHE_SHIFT;
-   unsigned pageFrom = pos & (PAGE_CACHE_SHIFT - 1);
-   unsigned pageTo = pos + len;
+   unsigned pageFrom = pos & (PAGE_CACHE_SIZE - 1);
+   unsigned pageTo = pageFrom + len;
    struct page *page;
 
    LOG(6, (KERN_WARNING "VMware hgfs: %s: (%s/%s(%ld), %u@%lld)\n",