libblkid: (erofs) make blocksize use more restrictive

* make sure we do not use any huge number when read from the device

* cleanup the code

Addresses: https://github.com/util-linux/util-linux/pull/1799
Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/libblkid/src/superblocks/erofs.c b/libblkid/src/superblocks/erofs.c
index a914704156cf63bb078669364160c7752347d414..559ce63c1482e0d9cfe318968e1b9262cca7c6cd 100644 (file)
--- a/libblkid/src/superblocks/erofs.c
+++ b/libblkid/src/superblocks/erofs.c
@@ -3,6 +3,8 @@
  *
  * This file may be redistributed under the terms of the
  * GNU Lesser General Public License
+ *
+ * https://www.kernel.org/doc/html/latest/filesystems/erofs.html
  */
 #include <stddef.h>
 #include <string.h>
@@ -42,18 +44,22 @@ struct erofs_super_block {
 static int erofs_verify_checksum(blkid_probe pr, const struct blkid_idmag *mag,
                const struct erofs_super_block *sb)
 {
+       uint32_t expected, csum;
+       size_t csummed_size;
+       unsigned char *csummed;
+
        if (!(le32_to_cpu(sb->feature_compat) & EROFS_FEATURE_SB_CSUM))
                return 1;
 
-       uint32_t expected = le32_to_cpu(sb->checksum);
+       expected = le32_to_cpu(sb->checksum);
+       csummed_size = (1U << sb->blkszbits) - EROFS_SUPER_OFFSET;
 
-       size_t csummed_size = (1U << sb->blkszbits) - EROFS_SUPER_OFFSET;
-       unsigned char *csummed = blkid_probe_get_sb_buffer(pr, mag, csummed_size);
+       csummed = blkid_probe_get_sb_buffer(pr, mag, csummed_size);
        if (!csummed)
                return 0;
 
        memset(csummed + offsetof(struct erofs_super_block, checksum), 0, sizeof(uint32_t));
-       uint32_t csum = crc32c(~0L, csummed, csummed_size);
+       csum = crc32c(~0L, csummed, csummed_size);
 
        return blkid_probe_verify_csum(pr, csum, expected);
 }
@@ -66,6 +72,10 @@ static int probe_erofs(blkid_probe pr, const struct blkid_idmag *mag)
        if (!sb)
                return errno ? -errno : BLKID_PROBE_NONE;
 
+       /* EROFS is restricted to 4KiB block size */
+       if ((1U << sb->blkszbits) > 4096)
+               return BLKID_PROBE_NONE;
+
        if (!erofs_verify_checksum(pr, mag, sb))
                return BLKID_PROBE_NONE;
 
@@ -74,11 +84,8 @@ static int probe_erofs(blkid_probe pr, const struct blkid_idmag *mag)
                                      sizeof(sb->volume_name));
 
        blkid_probe_set_uuid(pr, sb->uuid);
-
-       if (sb->blkszbits < 32){
-               blkid_probe_set_fsblocksize(pr, 1U << sb->blkszbits);
-               blkid_probe_set_block_size(pr, 1U << sb->blkszbits);
-       }
+       blkid_probe_set_fsblocksize(pr, 1U << sb->blkszbits);
+       blkid_probe_set_block_size(pr, 1U << sb->blkszbits);
 
        return BLKID_PROBE_OK;
 }