[syslinux] [PATCH v1 1/1] extlinux: fix memory leak

[Imran Zaman]

devname is put on heap for all cases to avoid memory
leak, and ease of use in future as well

Signed-off-by: Imran Zaman <imran.zaman at intel.com>
---
 extlinux/main.c | 50 +++++++++++++++++++++++++++++++++-----------------
 1 file changed, 33 insertions(+), 17 deletions(-)

diff --git a/extlinux/main.c b/extlinux/main.c
index bc7ded3..74f8d1f 100644
--- a/extlinux/main.c
+++ b/extlinux/main.c
@@ -779,7 +779,7 @@ static char * get_default_subvol(char * rootdir, char * subvol)
     struct btrfs_ioctl_search_key *sk = &args.key;
     struct btrfs_ioctl_search_header *sh;
     int ret, i;
-    int fd;
+    int fd = -1;
     struct btrfs_root_ref *ref;
     struct btrfs_dir_item *dir_item;
     unsigned long off = 0;
@@ -1044,12 +1044,12 @@ err:
 }
 
 #ifndef __KLIBC__
-static const char *find_device(const char *mtab_file, dev_t dev)
+static char *find_device(const char *mtab_file, dev_t dev)
 {
     struct mntent *mnt;
     struct stat dst;
     FILE *mtab;
-    const char *devname = NULL;
+    char *devname = NULL;
     bool done;
 
     mtab = setmntent(mtab_file, "r");
@@ -1131,7 +1131,7 @@ static const char *find_device(const char *mtab_file, dev_t dev)
  * On newer Linux kernels we can use sysfs to get a backwards mapping
  * from device names to standard filenames
  */
-static const char *find_device_sysfs(dev_t dev)
+static char *find_device_sysfs(dev_t dev)
 {
     char sysname[64];
     char linkname[PATH_MAX];
@@ -1281,9 +1281,20 @@ err:
     return rv;
 }
 
-static const char *get_devname(const char *path)
+static char *dupname(const char *name)
+{
+    char *out = NULL;
+    int len = 0;
+    if (name)
+        len = strlen(name);
+    if (len > 0)
+        out = strndup(name, len);
+    return out;
+}
+
+static char *get_devname(const char *path)
 {
-    const char *devname = NULL;
+    char *devname = NULL;
     struct stat st;
     struct statfs sfs;
 
@@ -1297,22 +1308,22 @@ static const char *get_devname(const char *path)
     }
 
     if (opt.device)
-	devname = opt.device;
+	devname = strdup(opt.device);
 
     if (!devname){
 	if (fs_type == BTRFS) {
 	    /* For btrfs try to get the device name from btrfs itself */
-	    devname = find_device_btrfs(path);
+	    devname = dupname(find_device_btrfs(path));
 	}
     }
 
     if (!devname) {
-	devname = find_device_mountinfo(path, st.st_dev);
+	devname = dupname(find_device_mountinfo(path, st.st_dev));
     }
 
 #ifdef __KLIBC__
     if (!devname) {
-	devname = find_device_sysfs(st.st_dev);
+	devname = dupname(find_device_sysfs(st.st_dev));
     }
     if (!devname) {
 	/* klibc doesn't have getmntent and friends; instead, just create
@@ -1326,7 +1337,7 @@ static const char *get_devname(const char *path)
 	}
 
 	atexit(device_cleanup);	/* unlink the device node on exit */
-	devname = devname_buf;
+	devname = dupname(devname_buf);
     }
 
 #else
@@ -1338,7 +1349,7 @@ static const char *get_devname(const char *path)
         devname = find_device("/etc/mtab", st.st_dev);
     }
     if (!devname) {
-	devname = find_device_sysfs(st.st_dev);
+	devname = dupname(find_device_sysfs(st.st_dev));
 
 	fprintf(stderr, "%s: cannot find device for path %s\n", program, path);
 	return devname;
@@ -1350,10 +1361,10 @@ static const char *get_devname(const char *path)
     return devname;
 }
 
-static int open_device(const char *path, struct stat *st, const char **_devname)
+static int open_device(const char *path, struct stat *st, char **_devname)
 {
     int devfd;
-    const char *devname = NULL;
+    char *devname = NULL;
     struct statfs sfs;
 
     if (st)
@@ -1393,11 +1404,10 @@ static int open_device(const char *path, struct stat *st, const char **_devname)
 
     devfd = -1;
     devname = get_devname(path);
-    if (_devname)
-	*_devname = devname;
 
     if ((devfd = open(devname, O_RDWR | O_SYNC)) < 0) {
 	fprintf(stderr, "%s: cannot open device %s\n", program, devname);
+	free(devname);
 	return -1;
     }
 
@@ -1405,9 +1415,14 @@ static int open_device(const char *path, struct stat *st, const char **_devname)
     if (validate_device(path, devfd)) {
 	fprintf(stderr, "%s: path %s doesn't match device %s\n",
 		program, path, devname);
+	free(devname);
 	close(devfd);
 	return -1;
     }
+    if (_devname)
+    	*_devname = devname;
+    else
+    	free(devname);
     return devfd;
 }
 
@@ -1468,7 +1483,7 @@ static int install_loader(const char *path, int update_only)
 {
     struct stat st, fst;
     int devfd, rv;
-    const char *devname;
+    char *devname = NULL;
 
     devfd = open_device(path, &st, &devname);
     if (devfd < 0)
@@ -1508,6 +1523,7 @@ static int install_loader(const char *path, int update_only)
 
     sync();
     rv = install_bootblock(devfd, devname);
+    free(devname);
     close(devfd);
     sync();
 
-- 
1.9.1

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