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net/sched: user-space can't set unknown tcfa_action values

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Currently, when initializing an action, the user-space can specify
and use arbitrary values for the tcfa_action field. If the value
is unknown by the kernel, is implicitly threaded as TC_ACT_UNSPEC.

This change explicitly checks for unknown values at action creation
time, and explicitly convert them to TC_ACT_UNSPEC. No functional
changes are introduced, but this will allow introducing tcfa_action
values not exposed to user-space in a later patch.

Note: we can't use the above to hide TC_ACT_REDIRECT from user-space,
as the latter is already part of uAPI.

v3 -> v4:
 - use an helper to check for action validity (JiriP)
 - emit an extack for invalid actions (JiriP)
v4 -> v5:
 - keep messages on a single line, drop net_warn (Marcelo)

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paolo Abeni 2018-07-30 14:30:42 +02:00 committed by David S. Miller
parent c87fffc57a
commit 802bfb1915
2 changed files with 18 additions and 2 deletions
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6
include/uapi/linux/pkt_cls.h
View file

@ -45,6 +45,7 @@ enum {
* the skb and act like everything
* is alright.
*/
#define TC_ACT_VALUE_MAX TC_ACT_TRAP
/* There is a special kind of actions called "extended actions",
* which need a value parameter. These have a local opcode located in
@ -55,11 +56,12 @@ enum {
#define __TC_ACT_EXT_SHIFT 28
#define __TC_ACT_EXT(local) ((local) << __TC_ACT_EXT_SHIFT)
#define TC_ACT_EXT_VAL_MASK ((1 << __TC_ACT_EXT_SHIFT) - 1)
#define TC_ACT_EXT_CMP(combined, opcode) \
(((combined) & (~TC_ACT_EXT_VAL_MASK)) == opcode)
#define TC_ACT_EXT_OPCODE(combined) ((combined) & (~TC_ACT_EXT_VAL_MASK))
#define TC_ACT_EXT_CMP(combined, opcode) (TC_ACT_EXT_OPCODE(combined) == opcode)
#define TC_ACT_JUMP __TC_ACT_EXT(1)
#define TC_ACT_GOTO_CHAIN __TC_ACT_EXT(2)
#define TC_ACT_EXT_OPCODE_MAX TC_ACT_GOTO_CHAIN
/* Action type identifiers*/
enum {

14
net/sched/act_api.c
View file

@ -786,6 +786,15 @@ static struct tc_cookie *nla_memdup_cookie(struct nlattr **tb)
return c;
}
static bool tcf_action_valid(int action)
{
int opcode = TC_ACT_EXT_OPCODE(action);
if (!opcode)
return action <= TC_ACT_VALUE_MAX;
return opcode <= TC_ACT_EXT_OPCODE_MAX || action == TC_ACT_UNSPEC;
}
struct tc_action *tcf_action_init_1(struct net *net, struct tcf_proto *tp,
struct nlattr *nla, struct nlattr *est,
char *name, int ovr, int bind,
@ -895,6 +904,11 @@ struct tc_action *tcf_action_init_1(struct net *net, struct tcf_proto *tp,
}
}
if (!tcf_action_valid(a->tcfa_action)) {
NL_SET_ERR_MSG(extack, "invalid action value, using TC_ACT_UNSPEC instead");
a->tcfa_action = TC_ACT_UNSPEC;
}
return a;
err_mod: