Hi, Looking at the crash some more, it seems that if value_len > PAGE_SIZE then e_buf->max_size is rounded up nearest page size [1]. If a new attribute is added with value_len < e_buf->max_size - EA_SIZE(ea) then no new space is allocated for the attiribute list [2] and this triggers the KASAN slab out of bounds error. This is the case in the C repro I provided.
1. https://elixir.bootlin.com/linux/v4.17-rc7/source/fs/jfs/xattr.c#L501 2. https://elixir.bootlin.com/linux/v4.17-rc7/source/fs/jfs/xattr.c#L723 On Fri, Jun 1, 2018 at 1:52 PM, shankarapailoor <shankarapail...@gmail.com> wrote: > Hi Dave et al, > > I have been fuzzing linux 4.17-rc4 with JFS using Syzkaller KASAN: > slab-out-of-bounds in jfs_xattr. > > Attached are my kernel configs and a C reproducer. In the first > setxattr call it appears that length is much larger than the name. In > __jfs_setxattr, I don't see where the length is checked against the > actual value length. > > Regards, > Shankara Pailoor -- Regards, Shankara Pailoor
