tree 0e77ba0fce0b9b68920ae7f7d1561ffcb690ba04
parent de9e9181bc066d63d78b768e95b5d949e2a8673a
author Theodore Ts'o <tytso@mit.edu> 1467763312 -0400
committer Theodore Ts'o <tytso@mit.edu> 1467763312 -0400

ext4: validate s_reserved_gdt_blocks on mount

If s_reserved_gdt_blocks is extremely large, it's possible for
ext4_init_block_bitmap(), which is called when ext4 sets up an
uninitialized block bitmap, to corrupt random kernel memory.  Add the
same checks which e2fsck has --- it must never be larger than
blocksize / sizeof(__u32) --- and then add a backup check in
ext4_init_block_bitmap() in case the superblock gets modified after
the file system is mounted.

Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org