Messages in this thread | | | Subject | Re: Slab out of bounds in setxattr | From | Dave Kleikamp <> | Date | Mon, 4 Jun 2018 13:24:34 -0500 |
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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 > <shankarapailoor@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 > > >
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