[PATCH nft] monitor: fix memleak in setelem cb

[PATCH nft] monitor: fix memleak in setelem cb

[Florian Westphal]

since 4521732ebbf3 ("monitor: missing cache and set handle initialization")
these fields are initied via handle_merge(), so don't clear them in
the json output case.  Fixes:

==31877==ERROR: LeakSanitizer: detected memory leaks
Direct leak of 16 byte(s) in 2 object(s) allocated from:
 #0 0x7f0cb9f29d4b in strdup asan/asan_interceptors.cpp:593
 #1 0x7f0cb9b584fd in xstrdup src/utils.c:80
 #2 0x7f0cb9b355b3 in handle_merge src/rule.c:127
 #3 0x7f0cb9ae12b8 in netlink_events_setelem_cb src/monitor.c:457

Seen when running tests/monitor with asan enabled.

Signed-off-by: Florian Westphal <fw@strlen.de>
---
 src/monitor.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/src/monitor.c b/src/monitor.c
index fafeeebe914b..6532c9c50f8d 100644
--- a/src/monitor.c
+++ b/src/monitor.c
@@ -496,13 +496,7 @@ static int netlink_events_setelem_cb(const struct nlmsghdr *nlh, int type,
 		nft_mon_print(monh, "\n");
 		break;
 	case NFTNL_OUTPUT_JSON:
-		dummyset->handle.family = family;
-		dummyset->handle.set.name = setname;
-		dummyset->handle.table.name = table;
 		monitor_print_element_json(monh, cmd, dummyset);
-		/* prevent set_free() from trying to free those */
-		dummyset->handle.set.name = NULL;
-		dummyset->handle.table.name = NULL;
 		if (!nft_output_echo(&monh->ctx->nft->output))
 			nft_mon_print(monh, "\n");
 		break;
-- 
2.52.0

Re: [PATCH nft] monitor: fix memleak in setelem cb

[Phil Sutter]

Hi,

On Wed, Jan 21, 2026 at 02:39:08PM +0100, Florian Westphal wrote:
> since 4521732ebbf3 ("monitor: missing cache and set handle initialization")
> these fields are initied via handle_merge(), so don't clear them in
> the json output case.  Fixes:
> 
> ==31877==ERROR: LeakSanitizer: detected memory leaks
> Direct leak of 16 byte(s) in 2 object(s) allocated from:
>  #0 0x7f0cb9f29d4b in strdup asan/asan_interceptors.cpp:593
>  #1 0x7f0cb9b584fd in xstrdup src/utils.c:80
>  #2 0x7f0cb9b355b3 in handle_merge src/rule.c:127
>  #3 0x7f0cb9ae12b8 in netlink_events_setelem_cb src/monitor.c:457
> 
> Seen when running tests/monitor with asan enabled.
> 
> Signed-off-by: Florian Westphal <fw@strlen.de>

Looks like a fix of commit 4521732ebbf34 ("monitor: missing cache and
set handle initialization")?

Cheers, Phil

Re: [PATCH nft] monitor: fix memleak in setelem cb

[Florian Westphal]

Phil Sutter <phil@nwl.cc> wrote:
> On Wed, Jan 21, 2026 at 02:39:08PM +0100, Florian Westphal wrote:
> > since 4521732ebbf3 ("monitor: missing cache and set handle initialization")
> > these fields are initied via handle_merge(), so don't clear them in
> > the json output case.  Fixes:
> > 
> > ==31877==ERROR: LeakSanitizer: detected memory leaks
> > Direct leak of 16 byte(s) in 2 object(s) allocated from:
> >  #0 0x7f0cb9f29d4b in strdup asan/asan_interceptors.cpp:593
> >  #1 0x7f0cb9b584fd in xstrdup src/utils.c:80
> >  #2 0x7f0cb9b355b3 in handle_merge src/rule.c:127
> >  #3 0x7f0cb9ae12b8 in netlink_events_setelem_cb src/monitor.c:457
> > 
> > Seen when running tests/monitor with asan enabled.
> > 
> > Signed-off-by: Florian Westphal <fw@strlen.de>
> 
> Looks like a fix of commit 4521732ebbf34 ("monitor: missing cache and
> set handle initialization")?

Yes