linux-kernel - [Revised PATCH v2] hv: kvp: Avoid reading past allocated blocks from KVP file

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Message-Id: <20171101184526.1689-1-longli@exchange.microsoft.com>
Date:   Wed,  1 Nov 2017 11:45:26 -0700
From:   Long Li <longli@...hange.microsoft.com>
To:     "K . Y . Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        devel@...uxdriverproject.org, linux-kernel@...r.kernel.org
Cc:     Paul Meyer <Paul.Meyer@...rosoft.com>,
        Long Li <longli@...rosoft.com>
Subject: [Revised PATCH v2] hv: kvp: Avoid reading past allocated blocks from KVP file

From: Paul Meyer <Paul.Meyer@...rosoft.com>

While reading in more than one block (50) of KVP records, the allocation
goes per block, but the reads used the total number of allocated records
(without resetting the pointer/stream). This causes the records buffer to
overrun when the refresh reads more than one block over the previous
capacity (e.g. reading more than 100 KVP records whereas the in-memory
database was empty before).

Fix this by reading the correct number of KVP records from file each time.

Changes since v1:
1. Properly wrapped comment texts.
2. Added the 2nd Signed-off-by.

Signed-off-by: Paul Meyer <Paul.Meyer@...rosoft.com>
Signed-off-by: Long Li <longli@...rosoft.com>
---
 tools/hv/hv_kvp_daemon.c | 66 ++++++++----------------------------------------
 1 file changed, 10 insertions(+), 56 deletions(-)

diff --git a/tools/hv/hv_kvp_daemon.c b/tools/hv/hv_kvp_daemon.c
index eaa3bec..2094036 100644
--- a/tools/hv/hv_kvp_daemon.c
+++ b/tools/hv/hv_kvp_daemon.c
@@ -193,11 +193,13 @@ static void kvp_update_mem_state(int pool)
 	for (;;) {
 		readp = &record[records_read];
 		records_read += fread(readp, sizeof(struct kvp_record),
-					ENTRIES_PER_BLOCK * num_blocks,
-					filep);
+				ENTRIES_PER_BLOCK * num_blocks - records_read,
+				filep);
 
 		if (ferror(filep)) {
-			syslog(LOG_ERR, "Failed to read file, pool: %d", pool);
+			syslog(LOG_ERR,
+				"Failed to read file, pool: %d; error: %d %s",
+				 pool, errno, strerror(errno));
 			exit(EXIT_FAILURE);
 		}
 
@@ -224,15 +226,11 @@ static void kvp_update_mem_state(int pool)
 	fclose(filep);
 	kvp_release_lock(pool);
 }
+
 static int kvp_file_init(void)
 {
 	int  fd;
-	FILE *filep;
-	size_t records_read;
 	char *fname;
-	struct kvp_record *record;
-	struct kvp_record *readp;
-	int num_blocks;
 	int i;
 	int alloc_unit = sizeof(struct kvp_record) * ENTRIES_PER_BLOCK;
 
@@ -246,61 +244,17 @@ static int kvp_file_init(void)
 
 	for (i = 0; i < KVP_POOL_COUNT; i++) {
 		fname = kvp_file_info[i].fname;
-		records_read = 0;
-		num_blocks = 1;
 		sprintf(fname, "%s/.kvp_pool_%d", KVP_CONFIG_LOC, i);
 		fd = open(fname, O_RDWR | O_CREAT | O_CLOEXEC, 0644 /* rw-r--r-- */);
 
 		if (fd == -1)
 			return 1;
 
-
-		filep = fopen(fname, "re");
-		if (!filep) {
-			close(fd);
-			return 1;
-		}
-
-		record = malloc(alloc_unit * num_blocks);
-		if (record == NULL) {
-			fclose(filep);
-			close(fd);
-			return 1;
-		}
-		for (;;) {
-			readp = &record[records_read];
-			records_read += fread(readp, sizeof(struct kvp_record),
-					ENTRIES_PER_BLOCK,
-					filep);
-
-			if (ferror(filep)) {
-				syslog(LOG_ERR, "Failed to read file, pool: %d",
-				       i);
-				exit(EXIT_FAILURE);
-			}
-
-			if (!feof(filep)) {
-				/*
-				 * We have more data to read.
-				 */
-				num_blocks++;
-				record = realloc(record, alloc_unit *
-						num_blocks);
-				if (record == NULL) {
-					fclose(filep);
-					close(fd);
-					return 1;
-				}
-				continue;
-			}
-			break;
-		}
 		kvp_file_info[i].fd = fd;
-		kvp_file_info[i].num_blocks = num_blocks;
-		kvp_file_info[i].records = record;
-		kvp_file_info[i].num_records = records_read;
-		fclose(filep);
-
+		kvp_file_info[i].num_blocks = 1;
+		kvp_file_info[i].records = malloc(alloc_unit);
+		kvp_file_info[i].num_records = 0;
+		kvp_update_mem_state(i);
 	}
 
 	return 0;
-- 
2.7.4