From: Rustam Kovhaev <rkovhaev@xxxxxxxxx> Subject: ntfs: add check for mft record size in superblock Number of bytes allocated for mft record should be equal to the mft record size stored in ntfs superblock as reported by syzbot, userspace might trigger out-of-bounds read by dereferencing ctx->attr in ntfs_attr_find() Link: https://syzkaller.appspot.com/bug?extid=aed06913f36eff9b544e Link: https://lkml.kernel.org/r/20200824022804.226242-1-rkovhaev@xxxxxxxxx Reported-by: syzbot+aed06913f36eff9b544e@xxxxxxxxxxxxxxxxxxxxxxxxx Tested-by: syzbot+aed06913f36eff9b544e@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Rustam Kovhaev <rkovhaev@xxxxxxxxx> Acked-by: Anton Altaparmakov <anton@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/ntfs/inode.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/fs/ntfs/inode.c~ntfs-add-check-for-mft-record-size-in-superblock +++ a/fs/ntfs/inode.c @@ -1810,6 +1810,12 @@ int ntfs_read_inode_mount(struct inode * brelse(bh); } + if (le32_to_cpu(m->bytes_allocated) != vol->mft_record_size) { + ntfs_error(sb, "Incorrect mft record size %u in superblock, should be %u.", + le32_to_cpu(m->bytes_allocated), vol->mft_record_size); + goto err_out; + } + /* Apply the mst fixups. */ if (post_read_mst_fixup((NTFS_RECORD*)m, vol->mft_record_size)) { /* FIXME: Try to use the $MFTMirr now. */ _
