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    Subject[PATCH 5.4 01/49] netfilter: nftables_offload: KASAN slab-out-of-bounds Read in nft_flow_rule_create
    Date
    From: Saeed Mirzamohammadi <saeed.mirzamohammadi@oracle.com>

    commit 31cc578ae2de19c748af06d859019dced68e325d upstream.

    This patch fixes the issue due to:

    BUG: KASAN: slab-out-of-bounds in nft_flow_rule_create+0x622/0x6a2
    net/netfilter/nf_tables_offload.c:40
    Read of size 8 at addr ffff888103910b58 by task syz-executor227/16244

    The error happens when expr->ops is accessed early on before performing the boundary check and after nft_expr_next() moves the expr to go out-of-bounds.

    This patch checks the boundary condition before expr->ops that fixes the slab-out-of-bounds Read issue.

    Add nft_expr_more() and use it to fix this problem.

    Signed-off-by: Saeed Mirzamohammadi <saeed.mirzamohammadi@oracle.com>
    Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    include/net/netfilter/nf_tables.h | 6 ++++++
    net/netfilter/nf_tables_api.c | 6 +++---
    net/netfilter/nf_tables_offload.c | 4 ++--
    3 files changed, 11 insertions(+), 5 deletions(-)

    --- a/include/net/netfilter/nf_tables.h
    +++ b/include/net/netfilter/nf_tables.h
    @@ -872,6 +872,12 @@ static inline struct nft_expr *nft_expr_
    return (struct nft_expr *)&rule->data[rule->dlen];
    }

    +static inline bool nft_expr_more(const struct nft_rule *rule,
    + const struct nft_expr *expr)
    +{
    + return expr != nft_expr_last(rule) && expr->ops;
    +}
    +
    static inline struct nft_userdata *nft_userdata(const struct nft_rule *rule)
    {
    return (void *)&rule->data[rule->dlen];
    --- a/net/netfilter/nf_tables_api.c
    +++ b/net/netfilter/nf_tables_api.c
    @@ -254,7 +254,7 @@ static void nft_rule_expr_activate(const
    struct nft_expr *expr;

    expr = nft_expr_first(rule);
    - while (expr != nft_expr_last(rule) && expr->ops) {
    + while (nft_expr_more(rule, expr)) {
    if (expr->ops->activate)
    expr->ops->activate(ctx, expr);

    @@ -269,7 +269,7 @@ static void nft_rule_expr_deactivate(con
    struct nft_expr *expr;

    expr = nft_expr_first(rule);
    - while (expr != nft_expr_last(rule) && expr->ops) {
    + while (nft_expr_more(rule, expr)) {
    if (expr->ops->deactivate)
    expr->ops->deactivate(ctx, expr, phase);

    @@ -2642,7 +2642,7 @@ static void nf_tables_rule_destroy(const
    * is called on error from nf_tables_newrule().
    */
    expr = nft_expr_first(rule);
    - while (expr != nft_expr_last(rule) && expr->ops) {
    + while (nft_expr_more(rule, expr)) {
    next = nft_expr_next(expr);
    nf_tables_expr_destroy(ctx, expr);
    expr = next;
    --- a/net/netfilter/nf_tables_offload.c
    +++ b/net/netfilter/nf_tables_offload.c
    @@ -37,7 +37,7 @@ struct nft_flow_rule *nft_flow_rule_crea
    struct nft_expr *expr;

    expr = nft_expr_first(rule);
    - while (expr->ops && expr != nft_expr_last(rule)) {
    + while (nft_expr_more(rule, expr)) {
    if (expr->ops->offload_flags & NFT_OFFLOAD_F_ACTION)
    num_actions++;

    @@ -61,7 +61,7 @@ struct nft_flow_rule *nft_flow_rule_crea
    ctx->net = net;
    ctx->dep.type = NFT_OFFLOAD_DEP_UNSPEC;

    - while (expr->ops && expr != nft_expr_last(rule)) {
    + while (nft_expr_more(rule, expr)) {
    if (!expr->ops->offload) {
    err = -EOPNOTSUPP;
    goto err_out;

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