linux-kernel - [PATCH 3.16 029/254] hv: kvp: Avoid reading past allocated blocks from KVP file

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Message-ID: <lsq.1519831218.90841535@decadent.org.uk>
Date:   Wed, 28 Feb 2018 15:20:18 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Long Li" <longli@...rosoft.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        "Paul Meyer" <Paul.Meyer@...rosoft.com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Subject: [PATCH 3.16 029/254] hv: kvp: Avoid reading past allocated blocks
 from KVP file

3.16.55-rc1 review patch.  If anyone has any objections, please let me know.

------------------

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

commit 297d6b6e56c2977fc504c61bbeeaa21296923f89 upstream.

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.

Signed-off-by: Paul Meyer <Paul.Meyer@...rosoft.com>
Signed-off-by: Long Li <longli@...rosoft.com>
Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 tools/hv/hv_kvp_daemon.c | 70 ++++++++++--------------------------------------
 1 file changed, 14 insertions(+), 56 deletions(-)

--- a/tools/hv/hv_kvp_daemon.c
+++ b/tools/hv/hv_kvp_daemon.c
@@ -196,11 +196,14 @@ static void kvp_update_mem_state(int poo
 	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));
+			kvp_release_lock(pool);
 			exit(EXIT_FAILURE);
 		}
 
@@ -213,6 +216,7 @@ static void kvp_update_mem_state(int poo
 
 			if (record == NULL) {
 				syslog(LOG_ERR, "malloc failed");
+				kvp_release_lock(pool);
 				exit(EXIT_FAILURE);
 			}
 			continue;
@@ -227,15 +231,11 @@ static void kvp_update_mem_state(int poo
 	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;
 
@@ -249,61 +249,19 @@ 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);
+		if (kvp_file_info[i].records == NULL)
+			return 1;
+		kvp_file_info[i].num_records = 0;
+		kvp_update_mem_state(i);
 	}
 
 	return 0;