Re: Subject: [PATCH] RDMA/rxe: bound the ODP page index against the umem in rxe_check_pagefault()

[Willy Tarreau <w@1wt.eu>]

On Wed, Sep 30, 2026 at 09:52:30AM -0700, Zhu Yanjun wrote:
> 
> ? 2026/9/30 7:01, AYS ??:
> > An ODP MR's page array map.pfn_list[] is sized from the umem's start, but
> > rxe_check_pagefault() indexes it with an iova taken relative to that start
> > while the access was range-checked against the MR's iova (ibmr.iova).
> > reg_mr
> > only requires start and hca_va to share a page offset, so a user can
> > register
> > with hca_va = start + N*PAGE, and the index skew (hca_va - start) >>
> > PAGE_SHIFT then lands out of bounds of pfn_list[], which is read with no
> > bound
> > check. An unprivileged local user reaches this with a single RDMA
> > operation on
> > a self-connected rxe QP: observed as a KASAN slab-out-of-bounds read
> > and, when
> > the out-of-bounds qword looks like a writable HMM pfn, a write into an
> > attacker-influenced page.
> > 
> > Reject an index that leaves the umem and force the fault path, which
> > fails the
> > out-of-range access via the umem range check in
> > ib_umem_odp_map_dma_and_lock(). The downstream pfn_list[] users
> > (__rxe_odp_mr_copy() and the atomic helpers) run only after a successful
> > map,
> > so this check protects them as well.
> > 
> > Fixes: 2fae67ab63db ("RDMA/rxe: Add support for Send/Recv/Write/Read
> > with ODP")
> > Signed-off-by: Youngsung Ahn <ays511.kr@gmail.com>
> > ---
> > Notes (not part of the commit):
> > Reproduced on a KASAN x86-64 build of 7.3-rc4 as uid 1000; the data-only
> > write
> > primitive was used to reach uid 0 on a fully hardened build.
> > drivers/infiniband/sw/rxe/ is unchanged between 7.3-rc4 (93f51579e7df) and
> > mainline 551c722f4080 (2026-09-29) and rdma for-next, so both are
> > affected.
> > Compile-tested (KASAN+RDMA_RXE), not runtime-tested. Found through
> > AI-assisted
> > review; per Documentation/process/security-bugs.rst this is public and a
> > reproducer can be shared on request. A maintainer may prefer to also index
> > relative to ibmr.iova (as the non-ODP rxe_mr_iova_to_index() does) so
> > legitimately skewed MRs keep working; this patch takes the minimal, safe
> > route.
> > 
> >  drivers/infiniband/sw/rxe/rxe_odp.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/drivers/infiniband/sw/rxe/rxe_odp.c
> > b/drivers/infiniband/sw/rxe/rxe_odp.c
> > index ab21b620e94c..07a30c60fc62 100644
> > --- a/drivers/infiniband/sw/rxe/rxe_odp.c
> > +++ b/drivers/infiniband/sw/rxe/rxe_odp.c
> > @@ -136,6 +136,11 @@ static inline bool rxe_check_pagefault(struct
> > ib_umem_odp *umem_odp, u64 iova,
> >   while (addr < iova + length) {
> >   idx = (addr - ib_umem_start(umem_odp)) >> umem_odp->page_shift;
> > 
> > + if (idx >= ib_umem_odp_num_pages(umem_odp)) {
> > + need_fault = true;
> > + break;
> > + }
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/coding-style.rst?h=v7.3-rc5
> 
> Please follow coding-style.rst to rewrite the above code snippet, then
> resend this commit.

I think it's not a coding style issue but an email encoding issue. Please
refer to Documentation/process/email-clients.rst to figure how to fix the
mailer's setup.

Willy