From 4b512e1c1f8de6b9ceb796ecef8658e0a083cab7 Mon Sep 17 00:00:00 2001 From: Liping Zhang Date: Sat, 23 Jul 2016 16:00:32 +0800 Subject: [PATCH] netfilter: nft_compat: fix crash when related match/target module is removed We "cache" the loaded match/target modules and reuse them, but when the modules are removed, we still point to them. Then we may end up with invalid memory references when using iptables-compat to add rules later. Input the following commands will reproduce the kernel crash: # iptables-compat -A INPUT -j LOG # iptables-compat -D INPUT -j LOG # rmmod xt_LOG # iptables-compat -A INPUT -j LOG BUG: unable to handle kernel paging request at ffffffffa05a9010 IP: [] strcmp+0xe/0x30 Call Trace: [] nft_target_select_ops+0x83/0x1f0 [nft_compat] [] nf_tables_expr_parse+0x147/0x1f0 [nf_tables] [] nf_tables_newrule+0x301/0x810 [nf_tables] [] ? nla_parse+0x20/0x100 [] nfnetlink_rcv+0x33f/0x53d [nfnetlink] [] ? nfnetlink_rcv+0x1fb/0x53d [nfnetlink] [] netlink_unicast+0x178/0x220 [] netlink_sendmsg+0x2fb/0x3a0 [] sock_sendmsg+0x38/0x50 [] ___sys_sendmsg+0x28e/0x2a0 [] ? release_sock+0x1e/0xb0 [] ? _raw_spin_unlock_bh+0x35/0x40 [] ? release_sock+0x82/0xb0 [] __sys_sendmsg+0x54/0x90 [] SyS_sendmsg+0x12/0x20 [] entry_SYSCALL_64_fastpath+0x1a/0xa9 So when nobody use the related match/target module, there's no need to "cache" it. And nft_[match|target]_release are useless anymore, remove them. Signed-off-by: Liping Zhang Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nft_compat.c | 43 ++++++++++++++++++-------------------- 1 file changed, 20 insertions(+), 23 deletions(-) diff --git a/net/netfilter/nft_compat.c b/net/netfilter/nft_compat.c index 2e07cec50ffd..c21e7eb8dce0 100644 --- a/net/netfilter/nft_compat.c +++ b/net/netfilter/nft_compat.c @@ -23,6 +23,20 @@ #include #include +struct nft_xt { + struct list_head head; + struct nft_expr_ops ops; + unsigned int refcnt; +}; + +static void nft_xt_put(struct nft_xt *xt) +{ + if (--xt->refcnt == 0) { + list_del(&xt->head); + kfree(xt); + } +} + static int nft_compat_chain_validate_dependency(const char *tablename, const struct nft_chain *chain) { @@ -260,6 +274,7 @@ nft_target_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr) if (par.target->destroy != NULL) par.target->destroy(&par); + nft_xt_put(container_of(expr->ops, struct nft_xt, ops)); module_put(target->me); } @@ -442,6 +457,7 @@ nft_match_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr) if (par.match->destroy != NULL) par.match->destroy(&par); + nft_xt_put(container_of(expr->ops, struct nft_xt, ops)); module_put(match->me); } @@ -612,11 +628,6 @@ static const struct nfnetlink_subsystem nfnl_compat_subsys = { static LIST_HEAD(nft_match_list); -struct nft_xt { - struct list_head head; - struct nft_expr_ops ops; -}; - static struct nft_expr_type nft_match_type; static bool nft_match_cmp(const struct xt_match *match, @@ -653,6 +664,7 @@ nft_match_select_ops(const struct nft_ctx *ctx, if (!try_module_get(match->me)) return ERR_PTR(-ENOENT); + nft_match->refcnt++; return &nft_match->ops; } } @@ -673,6 +685,7 @@ nft_match_select_ops(const struct nft_ctx *ctx, goto err; } + nft_match->refcnt = 1; nft_match->ops.type = &nft_match_type; nft_match->ops.size = NFT_EXPR_SIZE(XT_ALIGN(match->matchsize)); nft_match->ops.eval = nft_match_eval; @@ -690,14 +703,6 @@ err: return ERR_PTR(err); } -static void nft_match_release(void) -{ - struct nft_xt *nft_match, *tmp; - - list_for_each_entry_safe(nft_match, tmp, &nft_match_list, head) - kfree(nft_match); -} - static struct nft_expr_type nft_match_type __read_mostly = { .name = "match", .select_ops = nft_match_select_ops, @@ -744,6 +749,7 @@ nft_target_select_ops(const struct nft_ctx *ctx, if (!try_module_get(target->me)) return ERR_PTR(-ENOENT); + nft_target->refcnt++; return &nft_target->ops; } } @@ -764,6 +770,7 @@ nft_target_select_ops(const struct nft_ctx *ctx, goto err; } + nft_target->refcnt = 1; nft_target->ops.type = &nft_target_type; nft_target->ops.size = NFT_EXPR_SIZE(XT_ALIGN(target->targetsize)); nft_target->ops.init = nft_target_init; @@ -785,14 +792,6 @@ err: return ERR_PTR(err); } -static void nft_target_release(void) -{ - struct nft_xt *nft_target, *tmp; - - list_for_each_entry_safe(nft_target, tmp, &nft_target_list, head) - kfree(nft_target); -} - static struct nft_expr_type nft_target_type __read_mostly = { .name = "target", .select_ops = nft_target_select_ops, @@ -835,8 +834,6 @@ static void __exit nft_compat_module_exit(void) nfnetlink_subsys_unregister(&nfnl_compat_subsys); nft_unregister_expr(&nft_target_type); nft_unregister_expr(&nft_match_type); - nft_match_release(); - nft_target_release(); } MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_NFT_COMPAT); -- 2.20.1