volume_id/fat: careful with sector#, it may not fit in 32 bits. +91 bytes

volume_id/*: a bit of code shrink

3 files changed, 68 insertions, 66 deletions

diff --git a/util-linux/volume_id/fat.c b/util-linux/volume_id/fat.c
index 816d69d4c..0e0a57d62 100644
--- a/util-linux/volume_id/fat.c
+++ b/util-linux/volume_id/fat.c
@@ -245,7 +245,7 @@ int volume_id_probe_vfat(struct volume_id *id, uint64_t fat_partition_off)
         buf_size = dir_entries * sizeof(struct vfat_dir_entry);
         buf = volume_id_get_buffer(id, fat_partition_off + root_start_off, buf_size);
         if (buf == NULL)
-                goto found;
+                goto ret;
 
         label = get_attr_volume_id((struct vfat_dir_entry*) buf, dir_entries);
 
@@ -261,7 +261,7 @@ int volume_id_probe_vfat(struct volume_id *id, uint64_t fat_partition_off)
                 volume_id_set_label_string(id, vs->type.fat.label, 11);
         }
         volume_id_set_uuid(id, vs->type.fat.serno, UUID_DOS);
-        goto found;
+        goto ret;
 
  fat32:
         /* FAT32 root dir is a cluster chain like any other directory */
@@ -272,20 +272,20 @@ int volume_id_probe_vfat(struct volume_id *id, uint64_t fat_partition_off)
         next_cluster = root_cluster;
         maxloop = 100;
         while (--maxloop) {
-                uint32_t next_off_sct;
+                uint64_t next_off_sct;
                 uint64_t next_off;
                 uint64_t fat_entry_off;
                 int count;
 
                 dbg("next_cluster 0x%x", (unsigned)next_cluster);
-                next_off_sct = (next_cluster - 2) * vs->sectors_per_cluster;
+                next_off_sct = (uint64_t)(next_cluster - 2) * vs->sectors_per_cluster;
                 next_off = (start_data_sct + next_off_sct) * sector_size_bytes;
                 dbg("cluster offset 0x%llx", (unsigned long long) next_off);
 
                 /* get cluster */
                 buf = volume_id_get_buffer(id, fat_partition_off + next_off, buf_size);
                 if (buf == NULL)
-                        goto found;
+                        goto ret;
 
                 dir = (struct vfat_dir_entry*) buf;
                 count = buf_size / sizeof(struct vfat_dir_entry);
@@ -300,7 +300,7 @@ int volume_id_probe_vfat(struct volume_id *id, uint64_t fat_partition_off)
                 dbg("fat_entry_off 0x%llx", (unsigned long long)fat_entry_off);
                 buf = volume_id_get_buffer(id, fat_partition_off + fat_entry_off, buf_size);
                 if (buf == NULL)
-                        goto found;
+                        goto ret;
 
                 /* set next cluster */
                 next_cluster = le32_to_cpu(*(uint32_t*)buf) & 0x0fffffff;
@@ -323,7 +323,7 @@ int volume_id_probe_vfat(struct volume_id *id, uint64_t fat_partition_off)
         }
         volume_id_set_uuid(id, vs->type.fat32.serno, UUID_DOS);
 
- found:
+ ret:
 //      volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);
 //      id->type = "vfat";
 
diff --git a/util-linux/volume_id/util.c b/util-linux/volume_id/util.c
index c4d20ba47..1a1b3f92e 100644
--- a/util-linux/volume_id/util.c
+++ b/util-linux/volume_id/util.c
@@ -195,70 +195,73 @@ set:
  * It's better to ignore such fs and continue.  */
 void *volume_id_get_buffer(struct volume_id *id, uint64_t off, size_t len)
 {
-        ssize_t buf_len;
+        uint8_t *dst;
+        unsigned small_off;
+        ssize_t read_len;
+
+        dbg("get buffer off 0x%llx(%llu), len 0x%zx",
+                (unsigned long long) off, (unsigned long long) off, len);
 
-        dbg("get buffer off 0x%llx(%llu), len 0x%zx", (unsigned long long) off, (unsigned long long) off, len);
         /* check if requested area fits in superblock buffer */
-        if (off + len <= SB_BUFFER_SIZE) {
+        if (off + len <= SB_BUFFER_SIZE
+         /* && off <= SB_BUFFER_SIZE - want this paranoid overflow check? */
+        ) {
                 if (id->sbbuf == NULL) {
                         id->sbbuf = xmalloc(SB_BUFFER_SIZE);
                 }
+                small_off = off;
+                dst = id->sbbuf;
 
                 /* check if we need to read */
-                if ((off + len) > id->sbbuf_len) {
-                        dbg("read sbbuf len:0x%llx", (unsigned long long) (off + len));
-                        if (lseek(id->fd, 0, SEEK_SET) != 0) {
-                                dbg("seek(0) failed");
-                                return NULL;
-                        }
-                        buf_len = full_read(id->fd, id->sbbuf, off + len);
-                        if (buf_len < 0) {
-                                dbg("read failed (%s)", strerror(errno));
-                                return NULL;
-                        }
-                        dbg("got 0x%zx (%zi) bytes", buf_len, buf_len);
-                        id->sbbuf_len = buf_len;
-                        if ((uint64_t)buf_len < off + len) {
-                                dbg("requested 0x%zx bytes, got only 0x%zx bytes", len, buf_len);
-                                return NULL;
-                        }
-                }
+                len += off;
+                if (len <= id->sbbuf_len)
+                        goto ret; /* we already have it */
 
-                return &(id->sbbuf[off]);
+                dbg("read sbbuf len:0x%x", (unsigned) len);
+                id->sbbuf_len = len;
+                off = 0;
+                goto do_read;
         }
 
         if (len > SEEK_BUFFER_SIZE) {
                 dbg("seek buffer too small %d", SEEK_BUFFER_SIZE);
                 return NULL;
         }
-
-        /* get seek buffer */
-        if (id->seekbuf == NULL) {
-                id->seekbuf = xmalloc(SEEK_BUFFER_SIZE);
-        }
+        dst = id->seekbuf;
 
         /* check if we need to read */
-        if ((off < id->seekbuf_off) || ((off + len) > (id->seekbuf_off + id->seekbuf_len))) {
-                dbg("read seekbuf off:0x%llx len:0x%zx", (unsigned long long) off, len);
-                if (lseek(id->fd, off, SEEK_SET) != off) {
-                        dbg("seek(0x%llx) failed", (unsigned long long) off);
-                        return NULL;
-                }
-                buf_len = full_read(id->fd, id->seekbuf, len);
-                if (buf_len < 0) {
-                        dbg("read failed (%s)", strerror(errno));
-                        return NULL;
-                }
-                dbg("got 0x%zx (%zi) bytes", buf_len, buf_len);
-                id->seekbuf_off = off;
-                id->seekbuf_len = buf_len;
-                if ((size_t)buf_len < len) {
-                        dbg("requested 0x%zx bytes, got only 0x%zx bytes", len, buf_len);
-                        return NULL;
-                }
+        if ((off >= id->seekbuf_off)
+         && ((off + len) <= (id->seekbuf_off + id->seekbuf_len))
+        ) {
+                small_off = off - id->seekbuf_off; /* can't overflow */
+                goto ret; /* we already have it */
         }
 
-        return &(id->seekbuf[off - id->seekbuf_off]);
+        id->seekbuf_off = off;
+        id->seekbuf_len = len;
+        id->seekbuf = xrealloc(id->seekbuf, len);
+        small_off = 0;
+        dst = id->seekbuf;
+        dbg("read seekbuf off:0x%llx len:0x%zx",
+                                (unsigned long long) off, len);
+ do_read:
+        if (lseek(id->fd, off, SEEK_SET) != off) {
+                dbg("seek(0x%llx) failed", (unsigned long long) off);
+                goto err;
+        }
+        read_len = full_read(id->fd, dst, len);
+        if (read_len != len) {
+                dbg("requested 0x%x bytes, got 0x%x bytes",
+                                (unsigned) len, (unsigned) read_len);
+ err:
+                /* id->seekbuf_len or id->sbbuf_len is wrong now! Fixing.
+                 * Most likely user will not do any additional
+                 * calls anyway, it's a corrupted fs or something. */
+                volume_id_free_buffer(id);
+                return NULL;
+        }
+ ret:
+        return dst + small_off;
 }
 
 void volume_id_free_buffer(struct volume_id *id)
@@ -269,4 +272,5 @@ void volume_id_free_buffer(struct volume_id *id)
         free(id->seekbuf);
         id->seekbuf = NULL;
         id->seekbuf_len = 0;
+        id->seekbuf_off = 0; /* paranoia */
 }
diff --git a/util-linux/volume_id/volume_id_internal.h b/util-linux/volume_id/volume_id_internal.h
index 075ddb344..fe3547d13 100644
--- a/util-linux/volume_id/volume_id_internal.h
+++ b/util-linux/volume_id/volume_id_internal.h
@@ -61,6 +61,17 @@ struct volume_id_partition {
 #endif
 
 struct volume_id {
+        int             fd;
+//      int             fd_close:1;
+        size_t          sbbuf_len;
+        size_t          seekbuf_len;
+        uint8_t         *sbbuf;
+        uint8_t         *seekbuf;
+        uint64_t        seekbuf_off;
+#ifdef UNUSED_PARTITION_CODE
+        struct volume_id_partition *partitions;
+        size_t          partition_count;
+#endif
 //      uint8_t         label_raw[VOLUME_ID_LABEL_SIZE];
 //      size_t          label_raw_len;
         char            label[VOLUME_ID_LABEL_SIZE+1];
@@ -72,19 +83,6 @@ struct volume_id {
 //      smallint        usage_id;
 //      const char      *usage;
 //      const char      *type;
-
-#ifdef UNUSED_PARTITION_CODE
-        struct volume_id_partition *partitions;
-        size_t          partition_count;
-#endif
-
-        int             fd;
-        uint8_t         *sbbuf;
-        uint8_t         *seekbuf;
-        size_t          sbbuf_len;
-        uint64_t        seekbuf_off;
-        size_t          seekbuf_len;
-//      int             fd_close:1;
 };
 
 struct volume_id *volume_id_open_node(int fd);