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netfilter: nf_tables: fix use-after-free when deleting compat expressions

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nft_compat ops do not have static storage duration, unlike all other
expressions.

When nf_tables_expr_destroy() returns, expr->ops might have been
free'd already, so we need to store next address before calling
expression destructor.

For same reason, we can't deref match pointer after nft_xt_put().

This can be easily reproduced by adding msleep() before
nft_match_destroy() returns.

Fixes: 0ca743a559 ("netfilter: nf_tables: add compatibility layer for x_tables")
Reported-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2018-11-12 22:43:45 +01:00 committed by Pablo Neira Ayuso
parent 0fbcc5b568
commit 29e3880109
2 changed files with 5 additions and 3 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

5
net/netfilter/nf_tables_api.c
View file

@ -2457,7 +2457,7 @@ static int nf_tables_getrule(struct net *net, struct sock *nlsk,
static void nf_tables_rule_destroy(const struct nft_ctx *ctx, static void nf_tables_rule_destroy(const struct nft_ctx *ctx,
struct nft_rule *rule) struct nft_rule *rule)
{ {
struct nft_expr *expr; struct nft_expr *expr, *next;
/* /*
* Careful: some expressions might not be initialized in case this * Careful: some expressions might not be initialized in case this
@ -2465,8 +2465,9 @@ static void nf_tables_rule_destroy(const struct nft_ctx *ctx,
*/ */
expr = nft_expr_first(rule); expr = nft_expr_first(rule);
while (expr != nft_expr_last(rule) && expr->ops) { while (expr != nft_expr_last(rule) && expr->ops) {
next = nft_expr_next(expr);
nf_tables_expr_destroy(ctx, expr); nf_tables_expr_destroy(ctx, expr);
expr = nft_expr_next(expr); expr = next;
} }
kfree(rule); kfree(rule);
} }

3
net/netfilter/nft_compat.c
View file

@ -520,6 +520,7 @@ __nft_match_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr,
void *info) void *info)
{ {
struct xt_match *match = expr->ops->data; struct xt_match *match = expr->ops->data;
struct module *me = match->me;
struct xt_mtdtor_param par; struct xt_mtdtor_param par;
par.net = ctx->net; par.net = ctx->net;
@ -530,7 +531,7 @@ __nft_match_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr,
par.match->destroy(&par); par.match->destroy(&par);
if (nft_xt_put(container_of(expr->ops, struct nft_xt, ops))) if (nft_xt_put(container_of(expr->ops, struct nft_xt, ops)))
module_put(match->me); module_put(me);
} }
static void static void