[PATCH] Fix bug where garbage collection for nf_conncount is not skipped when jiffies wrap around

[PATCH] Fix bug where garbage collection for nf_conncount is not skipped when jiffies wrap around

[Jensen, Nicklas Bo]

nf_conncount is supposed to skip garbage collection if it has already run garbage collection in the same jiffy. Unfortunately, this is broken when jiffies wrap around which this patch fixes.

The problem is that last_gc in the nf_conncount_list struct is an u32, but jiffies is an unsigned long which is 8 bytes on my systems. When those two are compared it only works until last_gc wraps around.

See bug report https://bugzilla.netfilter.org/show_bug.cgi?id=1778 for more details.

Signed-off-by: Nicklas Bo Jensen <njensen@akamai.com>
---
 net/netfilter/nf_conncount.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nf_conncount.c b/net/netfilter/nf_conncount.c
index 4890af4dc263..ebe38ed2e6f4 100644
--- a/net/netfilter/nf_conncount.c
+++ b/net/netfilter/nf_conncount.c
@@ -132,7 +132,7 @@ static int __nf_conncount_add(struct net *net,
        struct nf_conn *found_ct;
        unsigned int collect = 0;

-       if (time_is_after_eq_jiffies((unsigned long)list->last_gc))
+       if ((u32)jiffies == list->last_gc)
                goto add_new_node;

        /* check the saved connections */
@@ -234,7 +234,7 @@ bool nf_conncount_gc_list(struct net *net,
        bool ret = false;

        /* don't bother if we just did GC */
-       if (time_is_after_eq_jiffies((unsigned long)READ_ONCE(list->last_gc)))
+       if ((u32)jiffies == READ_ONCE(list->last_gc))
                return false;

        /* don't bother if other cpu is already doing GC */
--
2.34.1

Re: [PATCH] Fix bug where garbage collection for nf_conncount is not skipped when jiffies wrap around

[Florian Westphal]

Jensen, Nicklas Bo <njensen@akamai.com> wrote:
> nf_conncount is supposed to skip garbage collection if it has already run garbage collection in the same jiffy. Unfortunately, this is broken when jiffies wrap around which this patch fixes.
> 
> The problem is that last_gc in the nf_conncount_list struct is an u32, but jiffies is an unsigned long which is 8 bytes on my systems. When those two are compared it only works until last_gc wraps around.
> 
> See bug report https://bugzilla.netfilter.org/show_bug.cgi?id=1778 for more details.
> 
> Signed-off-by: Nicklas Bo Jensen <njensen@akamai.com>

Reviewed-by: Florian Westphal <fw@strlen.de>

Re: [PATCH] Fix bug where garbage collection for nf_conncount is not skipped when jiffies wrap around

[Florian Westphal]

Jensen, Nicklas Bo <njensen@akamai.com> wrote:
> nf_conncount is supposed to skip garbage collection if it has already run garbage collection in the same jiffy. Unfortunately, this is broken when jiffies wrap around which this patch fixes.
> 
> The problem is that last_gc in the nf_conncount_list struct is an u32, but jiffies is an unsigned long which is 8 bytes on my systems. When those two are compared it only works until last_gc wraps around.
> 
> See bug report https://bugzilla.netfilter.org/show_bug.cgi?id=1778 for more details.

Fixes: d265929930e2 ("netfilter: nf_conncount: reduce unnecessary GC")

Re: [PATCH] Fix bug where garbage collection for nf_conncount is not skipped when jiffies wrap around

[Pablo Neira Ayuso]

On Thu, Feb 27, 2025 at 01:32:34PM +0000, Jensen, Nicklas Bo wrote:
> nf_conncount is supposed to skip garbage collection if it has already run garbage collection in the same jiffy. Unfortunately, this is broken when jiffies wrap around which this patch fixes.
> 
> The problem is that last_gc in the nf_conncount_list struct is an u32, but jiffies is an unsigned long which is 8 bytes on my systems. When those two are compared it only works until last_gc wraps around.
> 
> See bug report https://bugzilla.netfilter.org/show_bug.cgi?id=1778 for more details.

Applied as:

        ("netfilter: nf_conncount: garbage collection is not skipped when jiffies wrap around")