From: Michael Guralnik Date: Mon, 27 Apr 2026 11:02:35 +0000 (+0300) Subject: RDMA/core: Fix rereg_mr use-after-free race X-Git-Tag: v7.1-rc3~40^2~16 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1f3b337af2231b1e83c9052f771b201f5cbb9997;p=thirdparty%2Fkernel%2Flinux.git RDMA/core: Fix rereg_mr use-after-free race When a driver creates a new MR during rereg_user_mr, a race window exists between rdma_alloc_commit_uobject() for the new MR and the point where the code reads that MR to populate the response keys. A concurrent rereg_mr or destroy_mr could destroy the MR in this window and cause UAF in the first thread. Racing flow between two rereg_mr calls: CPU0 CPU1 ---- ---- rereg_user_mr(mr_handle) uobj_get_write(mr_handle) -> mr0 mr1 = driver→rereg() rdma_alloc_commit_uobject(mr1) // mr1 replaced mr0 and is unlocked uobj_put_destroy(mr0) rereg_user_mr(mr_handle) uobj_get_write(mr_handle) -> mr1 mr2 = driver→rereg() rdma_alloc_commit_uobject(mr2) // mr2 replaced mr1 and is unlocked uobj_put_destroy(mr1) // Destroys mr1! resp.lkey = mr1->lkey; // UAF - mr1 was freed! resp.rkey = mr1->rkey; // UAF - mr1 was freed! Fix by storing lkey/rkey in local variables before the new MR is unlocked and using the local variables to set the user response. Fixes: 6e0954b11c05 ("RDMA/uverbs: Allow drivers to create a new HW object during rereg_mr") Link: https://patch.msgid.link/r/20260427-security-bug-fixes-v3-4-4621fa52de0e@nvidia.com Signed-off-by: Michael Guralnik Reviewed-by: Maher Sanalla Signed-off-by: Edward Srouji Signed-off-by: Jason Gunthorpe --- diff --git a/drivers/infiniband/core/uverbs_cmd.c b/drivers/infiniband/core/uverbs_cmd.c index a768436ba468..91a62d2ade4d 100644 --- a/drivers/infiniband/core/uverbs_cmd.c +++ b/drivers/infiniband/core/uverbs_cmd.c @@ -778,6 +778,7 @@ static int ib_uverbs_rereg_mr(struct uverbs_attr_bundle *attrs) struct ib_pd *orig_pd; struct ib_pd *new_pd; struct ib_mr *new_mr; + u32 lkey, rkey; ret = uverbs_request(attrs, &cmd, sizeof(cmd)); if (ret) @@ -846,6 +847,8 @@ static int ib_uverbs_rereg_mr(struct uverbs_attr_bundle *attrs) new_mr->uobject = uobj; atomic_inc(&new_pd->usecnt); new_uobj->object = new_mr; + lkey = new_mr->lkey; + rkey = new_mr->rkey; rdma_restrack_new(&new_mr->res, RDMA_RESTRACK_MR); rdma_restrack_set_name(&new_mr->res, NULL); @@ -871,11 +874,13 @@ static int ib_uverbs_rereg_mr(struct uverbs_attr_bundle *attrs) mr->iova = cmd.hca_va; mr->length = cmd.length; } + lkey = mr->lkey; + rkey = mr->rkey; } memset(&resp, 0, sizeof(resp)); - resp.lkey = mr->lkey; - resp.rkey = mr->rkey; + resp.lkey = lkey; + resp.rkey = rkey; ret = uverbs_response(attrs, &resp, sizeof(resp));