Windows: cm_SetupStoreBIOD compute correct scanEnd

The algorithm used to ensure "chunk size" operations attempts to
enforce aligned chunks.  There are two problems:

 1. an aligned chunk range may extend beyond the end of the file.

 2. an aligned chunk might end before the requested length of the
    active write.

Protect against scanning beyond the end of the file and do not truncate
writes.

Change-Id: Ibe6caebd78f73d2c93bfef0dcebef379ca843994
Reviewed-on: http://gerrit.openafs.org/10625
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>

diff --git a/src/WINNT/afsd/cm_dcache.c b/src/WINNT/afsd/cm_dcache.c
index 6dc23fd0c4ba4bddee2fb26131ad93e5fa639e2d..21f52b5af19484ba5b083c6b6d3a3c7d7fb3093b 100644 (file)
--- a/src/WINNT/afsd/cm_dcache.c
+++ b/src/WINNT/afsd/cm_dcache.c
@@ -1015,9 +1015,13 @@ long cm_SetupStoreBIOD(cm_scache_t *scp, osi_hyper_t *inOffsetp, long inSize,
     osi_hyper_t scanStart;             /* where to start scan for dirty pages */
     osi_hyper_t scanEnd;               /* where to stop scan for dirty pages */
     osi_hyper_t firstModOffset;        /* offset of first modified page in range */
+    osi_hyper_t tblocksize;
     long temp;
     long code;
     long flags;                        /* flags to cm_SyncOp */
+    int blockSize = cm_data.blockSize; /* need a signed version */
+
+    tblocksize = ConvertLongToLargeInteger(cm_data.buf_blockSize);
 
     /* clear things out */
     biop->scp = scp;                   /* do not hold; held by caller */
@@ -1031,12 +1035,12 @@ long cm_SetupStoreBIOD(cm_scache_t *scp, osi_hyper_t *inOffsetp, long inSize,
 
     /* reserve a chunk's worth of buffers */
     lock_ReleaseWrite(&scp->rw);
-    biop->reserved = (cm_chunkSize / cm_data.buf_blockSize);
+    biop->reserved = (cm_chunkSize / blockSize);
     buf_ReserveBuffers(biop->reserved);
     lock_ObtainWrite(&scp->rw);
 
     bufp = NULL;
-    for (temp = 0; temp < inSize; temp += cm_data.buf_blockSize) {
+    for (temp = 0; temp < inSize; temp += blockSize) {
         thyper = ConvertLongToLargeInteger(temp);
         tbase = LargeIntegerAdd(*inOffsetp, thyper);
 
@@ -1060,7 +1064,7 @@ long cm_SetupStoreBIOD(cm_scache_t *scp, osi_hyper_t *inOffsetp, long inSize,
                 lock_ReleaseMutex(&bufp->mx);
                 buf_Release(bufp);
                 bufp = NULL;
-                buf_UnreserveBuffers(cm_chunkSize / cm_data.buf_blockSize);
+               buf_UnreserveBuffers(cm_chunkSize / blockSize);
                 return code;
             }
 
@@ -1101,7 +1105,7 @@ long cm_SetupStoreBIOD(cm_scache_t *scp, osi_hyper_t *inOffsetp, long inSize,
     osi_QAddH((osi_queue_t **) &biop->bufListp,
               (osi_queue_t **) &biop->bufListEndp,
               &qdp->q);
-    biop->length = cm_data.buf_blockSize;
+    biop->length = blockSize;
     firstModOffset = bufp->offset;
     biop->offset = firstModOffset;
     bufp = NULL;       /* this buffer and reference added to the queue */
@@ -1112,14 +1116,25 @@ long cm_SetupStoreBIOD(cm_scache_t *scp, osi_hyper_t *inOffsetp, long inSize,
     thyper = ConvertLongToLargeInteger(cm_chunkSize);
     scanEnd = LargeIntegerAdd(scanStart, thyper);
 
+    /* do not scan beyond the end of the file */
+    if (scanEnd.QuadPart > scp->length.QuadPart) {
+       scanEnd = scp->length;
+       scanEnd.LowPart &= (-blockSize);
+       if (scanEnd.LowPart < scp->length.LowPart)
+           scanEnd.LowPart += blockSize;
+    }
+
+    /* do not leave out a requested portion of the range */
+    if (scanEnd.QuadPart < inOffsetp->QuadPart + inSize) {
+       scanEnd.QuadPart = inOffsetp->QuadPart + inSize;
+    }
+
     flags = CM_SCACHESYNC_GETSTATUS
         | CM_SCACHESYNC_STOREDATA
         | CM_SCACHESYNC_BUFLOCKED;
 
     /* start by looking backwards until scanStart */
-    /* hyper version of cm_data.buf_blockSize */
-    thyper = ConvertLongToLargeInteger(cm_data.buf_blockSize);
-    tbase = LargeIntegerSubtract(firstModOffset, thyper);
+    tbase = LargeIntegerSubtract(firstModOffset, tblocksize);
     while(LargeIntegerGreaterThanOrEqualTo(tbase, scanStart)) {
         /* see if we can find the buffer */
         bufp = buf_Find(&scp->fid, &tbase);
@@ -1173,17 +1188,15 @@ long cm_SetupStoreBIOD(cm_scache_t *scp, osi_hyper_t *inOffsetp, long inSize,
        bufp = NULL;            /* added to the queue */
 
         /* update biod info describing the transfer */
-        biop->offset = LargeIntegerSubtract(biop->offset, thyper);
-        biop->length += cm_data.buf_blockSize;
+       biop->offset = LargeIntegerSubtract(biop->offset, tblocksize);
+       biop->length += blockSize;
 
         /* update loop pointer */
-        tbase = LargeIntegerSubtract(tbase, thyper);
+       tbase = LargeIntegerSubtract(tbase, tblocksize);
     }  /* while loop looking for pages preceding the one we found */
 
     /* now, find later dirty, contiguous pages, and add them to the list */
-    /* hyper version of cm_data.buf_blockSize */
-    thyper = ConvertLongToLargeInteger(cm_data.buf_blockSize);
-    tbase = LargeIntegerAdd(firstModOffset, thyper);
+    tbase = LargeIntegerAdd(firstModOffset, tblocksize);
     while(LargeIntegerLessThan(tbase, scanEnd)) {
         /* see if we can find the buffer */
         bufp = buf_Find(&scp->fid, &tbase);
@@ -1237,10 +1250,10 @@ long cm_SetupStoreBIOD(cm_scache_t *scp, osi_hyper_t *inOffsetp, long inSize,
        bufp = NULL;
 
         /* update biod info describing the transfer */
-        biop->length += cm_data.buf_blockSize;
+       biop->length += blockSize;
 
         /* update loop pointer */
-        tbase = LargeIntegerAdd(tbase, thyper);
+       tbase = LargeIntegerAdd(tbase, tblocksize);
     }  /* while loop looking for pages following the first page we found */
 
     /* finally, we're done */