On 06/04/2018 01:30 PM, shankarapailoor wrote: > Hi Dave, > > Attached is my proposed patch. It solves the problem as you suggest > and I don't see the KASAN complaint.
That looks good to me. Add a description and a Signed-off-by: and I'll get it pushed upstream. Thanks for finding this. Shaggy > > Regards, > Shankara > > On Mon, Jun 4, 2018 at 11:24 AM, Dave Kleikamp <dave.kleik...@oracle.com> > wrote: >> On 06/01/2018 11:06 PM, shankarapailoor wrote: >>> 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. >> >> I see the problem. It looks like we should be calculating max_size >> earlier and using that to call kmalloc(). (xattr.c#496) >> >> Shaggy >>> >>> >>> 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