Re: [PATCH v3] nfp: fix use-after-free in area_cache_get()

[Simon Horman]

On Wed, Dec 07, 2022 at 12:21:10PM +0000, Lee Jones wrote:
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> 
> On Wed, 10 Aug 2022, Jialiang Wang wrote:
> 
> > area_cache_get() is used to distribute cache->area and set cache->id,
> >  and if cache->id is not 0 and cache->area->kref refcount is 0, it will
> >  release the cache->area by nfp_cpp_area_release(). area_cache_get()
> >  set cache->id before cpp->op->area_init() and nfp_cpp_area_acquire().
> >
> > But if area_init() or nfp_cpp_area_acquire() fails, the cache->id is
> >  is already set but the refcount is not increased as expected. At this
> >  time, calling the nfp_cpp_area_release() will cause use-after-free.
> >
> > To avoid the use-after-free, set cache->id after area_init() and
> >  nfp_cpp_area_acquire() complete successfully.
> >
> > Note: This vulnerability is triggerable by providing emulated device
> >  equipped with specified configuration.
> >
> >  BUG: KASAN: use-after-free in nfp6000_area_init (/home/user/Kernel/v5.19
> > /x86_64/src/drivers/net/ethernet/netronome/nfp/nfpcore/nfp6000_pcie.c:760)
> >   Write of size 4 at addr ffff888005b7f4a0 by task swapper/0/1
> >
> >  Call Trace:
> >   <TASK>
> >  nfp6000_area_init (/home/user/Kernel/v5.19/x86_64/src/drivers/net
> > /ethernet/netronome/nfp/nfpcore/nfp6000_pcie.c:760)
> >  area_cache_get.constprop.8 (/home/user/Kernel/v5.19/x86_64/src/drivers
> > /net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:884)
> >
> >  Allocated by task 1:
> >  nfp_cpp_area_alloc_with_name (/home/user/Kernel/v5.19/x86_64/src/drivers
> > /net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:303)
> >  nfp_cpp_area_cache_add (/home/user/Kernel/v5.19/x86_64/src/drivers/net
> > /ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:802)
> >  nfp6000_init (/home/user/Kernel/v5.19/x86_64/src/drivers/net/ethernet
> > /netronome/nfp/nfpcore/nfp6000_pcie.c:1230)
> >  nfp_cpp_from_operations (/home/user/Kernel/v5.19/x86_64/src/drivers/net
> > /ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:1215)
> >  nfp_pci_probe (/home/user/Kernel/v5.19/x86_64/src/drivers/net/ethernet
> > /netronome/nfp/nfp_main.c:744)
> >
> >  Freed by task 1:
> >  kfree (/home/user/Kernel/v5.19/x86_64/src/mm/slub.c:4562)
> >  area_cache_get.constprop.8 (/home/user/Kernel/v5.19/x86_64/src/drivers
> > /net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:873)
> >  nfp_cpp_read (/home/user/Kernel/v5.19/x86_64/src/drivers/net/ethernet
> > /netronome/nfp/nfpcore/nfp_cppcore.c:924 /home/user/Kernel/v5.19/x86_64
> > /src/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c:973)
> >  nfp_cpp_readl (/home/user/Kernel/v5.19/x86_64/src/drivers/net/ethernet
> > /netronome/nfp/nfpcore/nfp_cpplib.c:48)
> >
> > Signed-off-by: Jialiang Wang <wangjialiang0806@xxxxxxx>
> 
> Any reason why this doesn't have a Fixes: tag applied and/or didn't
> get sent to Stable?
> 
> Looks as if this needs to go back as far as v4.19.
> 
> Fixes: 4cb584e0ee7df ("nfp: add CPP access core")
> 
> commit 02e1a114fdb71e59ee6770294166c30d437bf86a upstream.

Hi Lee,

>From my side this looks like an oversight.

> > ---
> >  drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c
> > index 34c0d2ddf9ef..a8286d0032d1 100644
> > --- a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c
> > +++ b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.c
> > @@ -874,7 +874,6 @@ area_cache_get(struct nfp_cpp *cpp, u32 id,
> >       }
> >
> >       /* Adjust the start address to be cache size aligned */
> > -     cache->id = id;
> >       cache->addr = addr & ~(u64)(cache->size - 1);
> >
> >       /* Re-init to the new ID and address */
> > @@ -894,6 +893,8 @@ area_cache_get(struct nfp_cpp *cpp, u32 id,
> >               return NULL;
> >       }
> >
> > +     cache->id = id;
> > +
> >  exit:
> >       /* Adjust offset */
> >       *offset = addr - cache->addr;
> 
> --
> Lee Jones [李琼斯]