From 4f8c94022f0bc3babd0a124c0a7dcdd7547bd94e Mon Sep 17 00:00:00 2001 From: Rustam Kovhaev Date: Tue, 13 Oct 2020 16:48:17 -0700 Subject: [PATCH] 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() Reported-by: syzbot+aed06913f36eff9b544e@syzkaller.appspotmail.com Signed-off-by: Rustam Kovhaev Signed-off-by: Andrew Morton Tested-by: syzbot+aed06913f36eff9b544e@syzkaller.appspotmail.com Acked-by: Anton Altaparmakov Link: https://syzkaller.appspot.com/bug?extid=aed06913f36eff9b544e Link: https://lkml.kernel.org/r/20200824022804.226242-1-rkovhaev@gmail.com Signed-off-by: Linus Torvalds --- fs/ntfs/inode.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/ntfs/inode.c b/fs/ntfs/inode.c index 9bb9f0952b18..caf563981532 100644 --- a/fs/ntfs/inode.c +++ b/fs/ntfs/inode.c @@ -1810,6 +1810,12 @@ int ntfs_read_inode_mount(struct inode *vi) 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. */