libblkid: (vfat) avoid modifying shared buffer

Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>

diff --git a/libblkid/src/superblocks/vfat.c b/libblkid/src/superblocks/vfat.c
index 6d3b09171e1f8001bc4ad92cd60c780a8d36a066..6b4a3ad069c7b6b37b16043cf7241fd7a501c41e 100644 (file)
--- a/libblkid/src/superblocks/vfat.c
+++ b/libblkid/src/superblocks/vfat.c
@@ -127,10 +127,9 @@ static const char *no_name = "NO NAME    ";
 /*
  * Look for LABEL (name) in the FAT root directory.
  */
-static unsigned char *search_fat_label(blkid_probe pr,
-                               uint64_t offset, uint32_t entries)
+static int search_fat_label(blkid_probe pr, uint64_t offset, uint32_t entries, unsigned char out[11])
 {
-       struct vfat_dir_entry *ent, *dir = NULL;
+       const struct vfat_dir_entry *ent, *dir = NULL;
        uint32_t i;
 
        DBG(LOWPROBE, ul_debug("\tlook for label in root-dir "
@@ -144,7 +143,7 @@ static unsigned char *search_fat_label(blkid_probe pr,
                                        (uint64_t) entries *
                                                sizeof(struct vfat_dir_entry));
                if (!dir)
-                       return NULL;
+                       return 0;
        }
 
        for (i = 0; i < entries; i++) {
@@ -173,12 +172,13 @@ static unsigned char *search_fat_label(blkid_probe pr,
                if ((ent->attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) ==
                    FAT_ATTR_VOLUME_ID) {
                        DBG(LOWPROBE, ul_debug("\tfound fs LABEL at entry %d", i));
-                       if (ent->name[0] == 0x05)
-                               ent->name[0] = 0xE5;
-                       return ent->name;
+                       memcpy(out, ent->name, 11);
+                       if (out[0] == 0x05)
+                               out[0] = 0xE5;
+                       return 1;
                }
        }
-       return NULL;
+       return 0;
 }
 
 static int fat_valid_superblock(blkid_probe pr,
@@ -330,11 +330,8 @@ static int probe_vfat(blkid_probe pr, const struct blkid_idmag *mag)
                uint32_t root_start = (reserved + fat_size) * sector_size;
                uint32_t root_dir_entries = unaligned_le16(&vs->vs_dir_entries);
 
-               vol_label = search_fat_label(pr, root_start, root_dir_entries);
-               if (vol_label) {
-                       memcpy(vol_label_buf, vol_label, 11);
+               if (search_fat_label(pr, root_start, root_dir_entries, vol_label_buf))
                        vol_label = vol_label_buf;
-               }
 
                if (ms->ms_ext_boot_sign == 0x29)
                        boot_label = ms->ms_label;
@@ -373,9 +370,7 @@ static int probe_vfat(blkid_probe pr, const struct blkid_idmag *mag)
 
                        count = buf_size / sizeof(struct vfat_dir_entry);
 
-                       vol_label = search_fat_label(pr, next_off, count);
-                       if (vol_label) {
-                               memcpy(vol_label_buf, vol_label, 11);
+                       if (search_fat_label(pr, next_off, count, vol_label_buf)) {
                                vol_label = vol_label_buf;
                                break;
                        }