[PATCH nft] evaluate: avoid double-free on error handling of bogus objref maps

[PATCH nft] evaluate: avoid double-free on error handling of bogus objref maps

[Florian Westphal]

commit 98c51aaac42b ("evaluate: bail out if anonymous concat set defines a non concat expression")
clears set->init to avoid a double-free.

Extend this to also handle object maps.
The included bogon triggers a double-free of set->init expression:

Error: unqualified type invalid specified in map definition. Try "typeof expression" instead of "type datatype".
ct helper set ct  saddr map { 1c3:: : "p", dead::beef : "myftp" }
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

This might not crash, depending on libc/malloc, but ASAN reports this:
==17728==ERROR: AddressSanitizer: heap-use-after-free on address 0x50b0000005e8 at ..
READ of size 4 at 0x50b0000005e8 thread T0
    #0 0x7f1be3cb7526 in expr_free src/expression.c:87
    #1 0x7f1be3cbdf29 in map_expr_destroy src/expression.c:1488
    #2 0x7f1be3cb74d5 in expr_destroy src/expression.c:80
    #3 0x7f1be3cb75c6 in expr_free src/expression.c:96
    #4 0x7f1be3d5925e in objref_stmt_destroy src/statement.c:331
    #5 0x7f1be3d5831f in stmt_free src/statement.c:56
    #6 0x7f1be3d583c2 in stmt_list_free src/statement.c:66
    #7 0x7f1be3d42805 in rule_free src/rule.c:495
    #8 0x7f1be3d48329 in cmd_free src/rule.c:1417
    #9 0x7f1be3cd2c7c in __nft_run_cmd_from_filename src/libnftables.c:759
    #10 0x7f1be3cd340c in nft_run_cmd_from_filename src/libnftables.c:847
    #11 0x55dcde0440be in main src/main.c:535

Signed-off-by: Florian Westphal <fw@strlen.de>
---
 src/evaluate.c                                        |  2 +-
 tests/shell/testcases/bogons/objref_double_free_crash | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)
 create mode 100644 tests/shell/testcases/bogons/objref_double_free_crash

diff --git a/src/evaluate.c b/src/evaluate.c
index 699891106cb9..204796d00800 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -137,7 +137,7 @@ static struct expr *implicit_set_declaration(struct eval_ctx *ctx,
 	handle_merge(&set->handle, &ctx->cmd->handle);
 
 	if (set_evaluate(ctx, set) < 0) {
-		if (set->flags & NFT_SET_MAP)
+		if (set->flags & (NFT_SET_MAP|NFT_SET_OBJECT))
 			set->init = NULL;
 		set_free(set);
 		return NULL;
diff --git a/tests/shell/testcases/bogons/objref_double_free_crash b/tests/shell/testcases/bogons/objref_double_free_crash
new file mode 100644
index 000000000000..52b0435bfddc
--- /dev/null
+++ b/tests/shell/testcases/bogons/objref_double_free_crash
@@ -0,0 +1,10 @@
+table arp test {
+	ct helper myftp {
+		type "ftp" protocol tcp
+		l3proto inet
+	}
+
+	chain y {
+		ct helper set ct  saddr map { 1c3:: : "p", dead::beef : "myftp" }
+	}
+}
-- 
2.49.0

Re: [PATCH nft] evaluate: avoid double-free on error handling of bogus objref maps

[Pablo Neira Ayuso]

On Tue, Jun 24, 2025 at 11:20:58PM +0200, Florian Westphal wrote:
> commit 98c51aaac42b ("evaluate: bail out if anonymous concat set defines a non concat expression")
> clears set->init to avoid a double-free.
> 
> Extend this to also handle object maps.
> The included bogon triggers a double-free of set->init expression:
> 
> Error: unqualified type invalid specified in map definition. Try "typeof expression" instead of "type datatype".
> ct helper set ct  saddr map { 1c3:: : "p", dead::beef : "myftp" }
>                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> This might not crash, depending on libc/malloc, but ASAN reports this:
> ==17728==ERROR: AddressSanitizer: heap-use-after-free on address 0x50b0000005e8 at ..
> READ of size 4 at 0x50b0000005e8 thread T0
>     #0 0x7f1be3cb7526 in expr_free src/expression.c:87
>     #1 0x7f1be3cbdf29 in map_expr_destroy src/expression.c:1488
>     #2 0x7f1be3cb74d5 in expr_destroy src/expression.c:80
>     #3 0x7f1be3cb75c6 in expr_free src/expression.c:96
>     #4 0x7f1be3d5925e in objref_stmt_destroy src/statement.c:331
>     #5 0x7f1be3d5831f in stmt_free src/statement.c:56
>     #6 0x7f1be3d583c2 in stmt_list_free src/statement.c:66
>     #7 0x7f1be3d42805 in rule_free src/rule.c:495
>     #8 0x7f1be3d48329 in cmd_free src/rule.c:1417
>     #9 0x7f1be3cd2c7c in __nft_run_cmd_from_filename src/libnftables.c:759
>     #10 0x7f1be3cd340c in nft_run_cmd_from_filename src/libnftables.c:847
>     #11 0x55dcde0440be in main src/main.c:535
> 
> Signed-off-by: Florian Westphal <fw@strlen.de>

Reviewed-by: Pablo Neira Ayuso <pablo@netfilter.org>