From 2f9874af7248b917772c8673054118267b3be415 Mon Sep 17 00:00:00 2001 From: Julia Denham Date: Mon, 11 Jul 2022 08:10:32 -0400 Subject: [KPATCH CVE-2022-32250] kpatch fixes for CVE-2022-1966 Content-type: text/plain Kernels: 4.18.0-372.9.1.el8 Changes since last build: arches: x86_64 ppc64le nf_tables_api.o: changed function: nft_expr_init nf_tables_api.o: changed function: nft_set_elem_expr_alloc --------------------------- Kpatch-MR: https://gitlab.com/redhat/prdsc/rhel/src/kpatch/rhel-8/-/merge_requests/53 Approved-by: Joe Lawrence (@joe.lawrence) Approved-by: Yannick Cote (@ycote1) Modifications: none commit afeaad78f78f7593e89f540a87b8796e8d705d57 Author: Phil Sutter Date: Thu Jun 2 20:58:22 2022 +0200 netfilter: nf_tables: disallow non-stateful expression in sets earlier Bugzilla: https://bugzilla.redhat.com/2092986 CVE: CVE-2022-32250 Y-Commit: cfb0d599ec74a88a5f02455616f96946defb849e O-Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2092987 Upstream Status: net.git commit 520778042ccca O-CVE: CVE-2022-32250 Conflicts: Upstream renamed info -> expr_info. commit 520778042ccca019f3ffa136dd0ca565c486cedd Author: Pablo Neira Ayuso Date: Wed May 25 10:36:38 2022 +0200 netfilter: nf_tables: disallow non-stateful expression in sets earlier Since 3e135cd499bf ("netfilter: nft_dynset: dynamic stateful expression instantiation"), it is possible to attach stateful expressions to set elements. cd5125d8f518 ("netfilter: nf_tables: split set destruction in deactivate and destroy phase") introduces conditional destruction on the object to accomodate transaction semantics. nft_expr_init() calls expr->ops->init() first, then check for NFT_STATEFUL_EXPR, this stills allows to initialize a non-stateful lookup expressions which points to a set, which might lead to UAF since the set is not properly detached from the set->binding for this case. Anyway, this combination is non-sense from nf_tables perspective. This patch fixes this problem by checking for NFT_STATEFUL_EXPR before expr->ops->init() is called. The reporter provides a KASAN splat and a poc reproducer (similar to those autogenerated by syzbot to report use-after-free errors). It is unknown to me if they are using syzbot or if they use similar automated tool to locate the bug that they are reporting. For the record, this is the KASAN splat. [ 85.431824] ================================================================== [ 85.432901] BUG: KASAN: use-after-free in nf_tables_bind_set+0x81b/0xa20 [ 85.433825] Write of size 8 at addr ffff8880286f0e98 by task poc/776 [ 85.434756] [ 85.434999] CPU: 1 PID: 776 Comm: poc Tainted: G W 5.18.0+ #2 [ 85.436023] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014 Fixes: 0b2d8a7b638b ("netfilter: nf_tables: add helper functions for expression handling") Reported-and-tested-by: Aaron Adams Signed-off-by: Pablo Neira Ayuso Signed-off-by: Phil Sutter Signed-off-by: Augusto Caringi Signed-off-by: Julia Denham --- net/netfilter/nf_tables_api.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c index aa095db8d0ca..097680c5f914 100644 --- a/net/netfilter/nf_tables_api.c +++ b/net/netfilter/nf_tables_api.c @@ -2576,27 +2576,31 @@ static struct nft_expr *nft_expr_init(const struct nft_ctx *ctx, err = nf_tables_expr_parse(ctx, nla, &info); if (err < 0) - goto err1; + goto err_expr_parse; + + err = -EOPNOTSUPP; + if (!(info.ops->type->flags & NFT_EXPR_STATEFUL)) + goto err_expr_stateful; err = -ENOMEM; expr = kzalloc(info.ops->size, GFP_KERNEL); if (expr == NULL) - goto err2; + goto err_expr_stateful; err = nf_tables_newexpr(ctx, &info, expr); if (err < 0) - goto err3; + goto err_expr_new; return expr; -err3: +err_expr_new: kfree(expr); -err2: +err_expr_stateful: owner = info.ops->type->owner; if (info.ops->type->release_ops) info.ops->type->release_ops(info.ops); module_put(owner); -err1: +err_expr_parse: return ERR_PTR(err); } @@ -4983,9 +4987,6 @@ struct nft_expr *nft_set_elem_expr_alloc(const struct nft_ctx *ctx, return expr; err = -EOPNOTSUPP; - if (!(expr->ops->type->flags & NFT_EXPR_STATEFUL)) - goto err_set_elem_expr; - if (expr->ops->type->flags & NFT_EXPR_GC) { if (set->flags & NFT_SET_TIMEOUT) goto err_set_elem_expr; -- 2.26.3