From ae36a5b609ae79f4de966328b78d2584be9719a4 Mon Sep 17 00:00:00 2001 From: Norbert Szetei Date: Thu, 27 Aug 2026 19:18:07 +0200 Subject: [PATCH] RDMA/rxe: validate access flags before swapping the MR's PD rxe_rereg_user_mr() reassigns mr->ibmr.pd first and only then validates the IB_MR_REREG_ACCESS argument: if (flags & IB_MR_REREG_PD) { rxe_put(old_pd); rxe_get(pd); mr->ibmr.pd = ibpd; } if (flags & IB_MR_REREG_ACCESS) { if (access & ~RXE_ACCESS_SUPPORTED_MR) return ERR_PTR(-EOPNOTSUPP); mr->access = access; } Both flags pass the entry check because RXE_MR_REREG_SUPPORTED is IB_MR_REREG_PD | IB_MR_REREG_ACCESS, so a caller can reach the access check with mr->ibmr.pd already reassigned. mr->ibmr.pd is owned by the core, which adjusts pd->usecnt only on the success path: ib_uverbs_rereg_mr() jumps to put_new_uobj on a driver error without undoing the reassignment, so mr->pd == new_pd while the usecnts still charge the MR to orig_pd. ib_dereg_mr_user() then decrements new_pd, whose count can reach zero while a memory window still references it; uverbs_free_pd() frees the PD on that count alone and rxe_mw_cleanup() writes to freed memory: BUG: KASAN: slab-use-after-free in __rxe_put+0x31/0xa0 Write of size 4 at addr ffff8881301dd690 by task rxe_poc/591 __rxe_put+0x31/0xa0 rxe_mw_cleanup+0x42/0x200 __rxe_cleanup+0x115/0x370 rxe_dealloc_mw+0x4c/0x80 Allocated by task 591: ib_uverbs_alloc_pd+0x258/0x540 Freed by task 591: ib_dealloc_pd_user+0x174/0x210 uverbs_free_pd+0x8d/0xc0 ib_uverbs_dealloc_pd+0x18e/0x1d0 Validate the access flags before mutating any state so the callback either applies every requested change or none. Fixes: 544c7f62cf32 ("RDMA/rxe: Implement rereg_user_mr") Signed-off-by: Norbert Szetei Link: https://patch.msgid.link/46E1D5C0-24BE-4D01-BDB3-634FE09B22C5@doyensec.com Reviewed-by: Zhu Yanjun Signed-off-by: Leon Romanovsky --- drivers/infiniband/sw/rxe/rxe_verbs.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.c b/drivers/infiniband/sw/rxe/rxe_verbs.c index 96c7716057fe..3864284522eb 100644 --- a/drivers/infiniband/sw/rxe/rxe_verbs.c +++ b/drivers/infiniband/sw/rxe/rxe_verbs.c @@ -1331,19 +1331,20 @@ static struct ib_mr *rxe_rereg_user_mr(struct ib_mr *ibmr, int flags, if (err) return ERR_PTR(err); + if ((flags & IB_MR_REREG_ACCESS) && + (access & ~RXE_ACCESS_SUPPORTED_MR)) { + rxe_err_mr(mr, "access = %#x not supported\n", access); + return ERR_PTR(-EOPNOTSUPP); + } + if (flags & IB_MR_REREG_PD) { rxe_put(old_pd); rxe_get(pd); mr->ibmr.pd = ibpd; } - if (flags & IB_MR_REREG_ACCESS) { - if (access & ~RXE_ACCESS_SUPPORTED_MR) { - rxe_err_mr(mr, "access = %#x not supported\n", access); - return ERR_PTR(-EOPNOTSUPP); - } + if (flags & IB_MR_REREG_ACCESS) mr->access = access; - } return NULL; }