On Sun, Aug 18, 2019 at 07:38:47AM +0800, Gao Xiang wrote: > Hi Richard, > > On Sun, Aug 18, 2019 at 01:25:58AM +0200, Richard Weinberger wrote: [] > > > > While digging a little into the code I noticed that you have very few > > checks of the on-disk data. > > For example ->u.i_blkaddr. I gave it a try and created a > > malformed filesystem where u.i_blkaddr is 0xdeadbeef, it causes the kernel > > to loop forever around erofs_read_raw_page(). > > I don't fuzz all the on-disk fields for EROFS, I will do later.. > You can see many in-kernel filesystems are still hardening the related > stuff. Anyway, I will dig into this field you mentioned recently, but > I think it can be fixed easily later. ...I take a simple try with the following erofs-utils diff and a directory containing enwik9 only, with the latest kernel (5.3-rc) and command line is mkfs/mkfs.erofs -d9 enwik9.img testdir. diff --git a/lib/inode.c b/lib/inode.c index 581f263..2540338 100644 --- a/lib/inode.c +++ b/lib/inode.c @@ -388,8 +388,7 @@ static bool erofs_bh_flush_write_inode(struct erofs_buffer_head *bh) v1.i_u.compressed_blocks = cpu_to_le32(inode->u.i_blocks); else - v1.i_u.raw_blkaddr = - cpu_to_le32(inode->u.i_blkaddr); + v1.i_u.raw_blkaddr = 0xdeadbeef; break; } I tested the corrupted image with looped device and real blockdevice by dd, and it seems fine.... [36283.012381] erofs: initializing erofs 1.0 [36283.012510] erofs: successfully to initialize erofs [36283.012975] erofs: read_super, device -> /dev/loop17 [36283.012976] erofs: options -> (null) [36283.012983] erofs: root inode @ nid 36 [36283.012995] erofs: mounted on /dev/loop17 with opts: (null). [36297.354090] attempt to access beyond end of device [36297.354098] loop17: rw=0, want=29887428984, limit=1953128 [36297.354107] attempt to access beyond end of device [36297.354109] loop17: rw=0, want=29887428480, limit=1953128 [36301.827234] attempt to access beyond end of device [36301.827243] loop17: rw=0, want=29887428480, limit=1953128 [36371.426889] erofs: unmounted for /dev/loop17 [36518.156114] erofs: read_super, device -> /dev/nvme0n1p4 [36518.156115] erofs: options -> (null) [36518.156260] erofs: root inode @ nid 36 [36518.156384] erofs: mounted on /dev/nvme0n1p4 with opts: (null). [36522.818884] attempt to access beyond end of device [36522.818889] nvme0n1p4: rw=0, want=29887428984, limit=62781440 [36522.818895] attempt to access beyond end of device [36522.818896] nvme0n1p4: rw=0, want=29887428480, limit=62781440 [36524.072018] attempt to access beyond end of device [36524.072028] nvme0n1p4: rw=0, want=29887428480, limit=62781440 Could you give me more hints how to reproduce that? and I will dig into more maybe it needs more conditions... Thanks, Gao Xiang > > Thanks, > Gao Xiang > > > > > Thanks, > > //richard
