This is a note to let you know that I've just added the patch titled ntfs: add check for mft record size in superblock to the 5.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: ntfs-add-check-for-mft-record-size-in-superblock.patch and it can be found in the queue-5.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 6cab50e34684e428a40b3f8a1d94b9ca1e4b0b02 Author: Rustam Kovhaev <rkovhaev@xxxxxxxxx> Date: Tue Oct 13 16:48:17 2020 -0700 ntfs: add check for mft record size in superblock [ Upstream commit 4f8c94022f0bc3babd0a124c0a7dcdd7547bd94e ] 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@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Rustam Kovhaev <rkovhaev@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Tested-by: syzbot+aed06913f36eff9b544e@xxxxxxxxxxxxxxxxxxxxxxxxx Acked-by: Anton Altaparmakov <anton@xxxxxxxxxx> Link: https://syzkaller.appspot.com/bug?extid=aed06913f36eff9b544e Link: https://lkml.kernel.org/r/20200824022804.226242-1-rkovhaev@xxxxxxxxx Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/fs/ntfs/inode.c b/fs/ntfs/inode.c index 9bb9f0952b186..caf563981532b 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. */