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[v2,2/3] bpf: do not walk twice the hash map on free

Message ID 20240430-bpf-next-v2-2-140aa50f0f19@kernel.org (mailing list archive)
State Superseded
Delegated to: BPF
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Series bpf_wq followup series | expand

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Commit Message

Benjamin Tissoires April 30, 2024, 9:36 a.m. UTC 
If someone stores both a timer and a workqueue in a hash map, on free, we
would walk it twice.
Add a check in htab_free_malloced_timers_or_wq and free the timers
and workqueues if they are present.

Fixes: 246331e3f1ea ("bpf: allow struct bpf_wq to be embedded in arraymaps and hashmaps")
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>

---

changes in v2:
- fix wq being not freed (and static call not used)
---
 kernel/bpf/hashtab.c | 49 +++++++++++++------------------------------------
 1 file changed, 13 insertions(+), 36 deletions(-)

Comments

Benjamin Tissoires April 30, 2024, 10:39 a.m. UTC | #1 
On Apr 30 2024, Benjamin Tissoires wrote:
> If someone stores both a timer and a workqueue in a hash map, on free, we
> would walk it twice.
> Add a check in htab_free_malloced_timers_or_wq and free the timers
> and workqueues if they are present.
> 
> Fixes: 246331e3f1ea ("bpf: allow struct bpf_wq to be embedded in arraymaps and hashmaps")
> Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
> 
> ---
> 
> changes in v2:
> - fix wq being not freed (and static call not used)
> ---
>  kernel/bpf/hashtab.c | 49 +++++++++++++------------------------------------
>  1 file changed, 13 insertions(+), 36 deletions(-)
> 
> diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
> index 0179183c543a..5eefadfc8ea9 100644
> --- a/kernel/bpf/hashtab.c
> +++ b/kernel/bpf/hashtab.c
> @@ -221,32 +221,11 @@ static bool htab_has_extra_elems(struct bpf_htab *htab)
>  	return !htab_is_percpu(htab) && !htab_is_lru(htab);
>  }
>  
> -static void htab_free_prealloced_timers(struct bpf_htab *htab)
> +static void htab_free_prealloced_timers_and_wq(struct bpf_htab *htab)
>  {
>  	u32 num_entries = htab->map.max_entries;
>  	int i;
>  
> -	if (!btf_record_has_field(htab->map.record, BPF_TIMER))
> -		return;
> -	if (htab_has_extra_elems(htab))
> -		num_entries += num_possible_cpus();
> -
> -	for (i = 0; i < num_entries; i++) {
> -		struct htab_elem *elem;
> -
> -		elem = get_htab_elem(htab, i);
> -		bpf_obj_free_timer(htab->map.record, elem->key + round_up(htab->map.key_size, 8));
> -		cond_resched();
> -	}
> -}
> -
> -static void htab_free_prealloced_wq(struct bpf_htab *htab)
> -{
> -	u32 num_entries = htab->map.max_entries;
> -	int i;
> -
> -	if (!btf_record_has_field(htab->map.record, BPF_WORKQUEUE))
> -		return;
>  	if (htab_has_extra_elems(htab))
>  		num_entries += num_possible_cpus();
>  
> @@ -254,8 +233,12 @@ static void htab_free_prealloced_wq(struct bpf_htab *htab)
>  		struct htab_elem *elem;
>  
>  		elem = get_htab_elem(htab, i);
> -		bpf_obj_free_workqueue(htab->map.record,
> -				       elem->key + round_up(htab->map.key_size, 8));
> +		if (btf_record_has_field(htab->map.record, BPF_TIMER))
> +			bpf_obj_free_timer(htab->map.record,
> +					   elem->key + round_up(htab->map.key_size, 8));
> +		else

Sorry, this else above is wrong, it should be a check on BPF_WORKQUEUE
instead.

v3 is n its way (with the proper bpf-next suffix this time).

Cheers,
Benjamin

> +			bpf_obj_free_workqueue(htab->map.record,
> +					       elem->key + round_up(htab->map.key_size, 8));
>  		cond_resched();
>  	}
>  }
> @@ -1515,7 +1498,7 @@ static void delete_all_elements(struct bpf_htab *htab)
>  	migrate_enable();
>  }
>  
> -static void htab_free_malloced_timers_or_wq(struct bpf_htab *htab, bool is_timer)
> +static void htab_free_malloced_timers_and_wq(struct bpf_htab *htab)
>  {
>  	int i;
>  
> @@ -1527,10 +1510,10 @@ static void htab_free_malloced_timers_or_wq(struct bpf_htab *htab, bool is_timer
>  
>  		hlist_nulls_for_each_entry(l, n, head, hash_node) {
>  			/* We only free timer on uref dropping to zero */
> -			if (is_timer)
> +			if (btf_record_has_field(htab->map.record, BPF_TIMER))
>  				bpf_obj_free_timer(htab->map.record,
>  						   l->key + round_up(htab->map.key_size, 8));
> -			else
> +			if (btf_record_has_field(htab->map.record, BPF_WORKQUEUE))
>  				bpf_obj_free_workqueue(htab->map.record,
>  						       l->key + round_up(htab->map.key_size, 8));
>  		}
> @@ -1544,17 +1527,11 @@ static void htab_map_free_timers_and_wq(struct bpf_map *map)
>  	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
>  
>  	/* We only free timer and workqueue on uref dropping to zero */
> -	if (btf_record_has_field(htab->map.record, BPF_TIMER)) {
> -		if (!htab_is_prealloc(htab))
> -			htab_free_malloced_timers_or_wq(htab, true);
> -		else
> -			htab_free_prealloced_timers(htab);
> -	}
> -	if (btf_record_has_field(htab->map.record, BPF_WORKQUEUE)) {
> +	if (btf_record_has_field(htab->map.record, BPF_TIMER | BPF_WORKQUEUE)) {
>  		if (!htab_is_prealloc(htab))
> -			htab_free_malloced_timers_or_wq(htab, false);
> +			htab_free_malloced_timers_and_wq(htab);
>  		else
> -			htab_free_prealloced_wq(htab);
> +			htab_free_prealloced_timers_and_wq(htab);
>  	}
>  }
>  
> 
> -- 
> 2.44.0
>
diff mbox series

Patch

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 0179183c543a..5eefadfc8ea9 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -221,32 +221,11 @@  static bool htab_has_extra_elems(struct bpf_htab *htab)
 	return !htab_is_percpu(htab) && !htab_is_lru(htab);
 }
 
-static void htab_free_prealloced_timers(struct bpf_htab *htab)
+static void htab_free_prealloced_timers_and_wq(struct bpf_htab *htab)
 {
 	u32 num_entries = htab->map.max_entries;
 	int i;
 
-	if (!btf_record_has_field(htab->map.record, BPF_TIMER))
-		return;
-	if (htab_has_extra_elems(htab))
-		num_entries += num_possible_cpus();
-
-	for (i = 0; i < num_entries; i++) {
-		struct htab_elem *elem;
-
-		elem = get_htab_elem(htab, i);
-		bpf_obj_free_timer(htab->map.record, elem->key + round_up(htab->map.key_size, 8));
-		cond_resched();
-	}
-}
-
-static void htab_free_prealloced_wq(struct bpf_htab *htab)
-{
-	u32 num_entries = htab->map.max_entries;
-	int i;
-
-	if (!btf_record_has_field(htab->map.record, BPF_WORKQUEUE))
-		return;
 	if (htab_has_extra_elems(htab))
 		num_entries += num_possible_cpus();
 
@@ -254,8 +233,12 @@  static void htab_free_prealloced_wq(struct bpf_htab *htab)
 		struct htab_elem *elem;
 
 		elem = get_htab_elem(htab, i);
-		bpf_obj_free_workqueue(htab->map.record,
-				       elem->key + round_up(htab->map.key_size, 8));
+		if (btf_record_has_field(htab->map.record, BPF_TIMER))
+			bpf_obj_free_timer(htab->map.record,
+					   elem->key + round_up(htab->map.key_size, 8));
+		else
+			bpf_obj_free_workqueue(htab->map.record,
+					       elem->key + round_up(htab->map.key_size, 8));
 		cond_resched();
 	}
 }
@@ -1515,7 +1498,7 @@  static void delete_all_elements(struct bpf_htab *htab)
 	migrate_enable();
 }
 
-static void htab_free_malloced_timers_or_wq(struct bpf_htab *htab, bool is_timer)
+static void htab_free_malloced_timers_and_wq(struct bpf_htab *htab)
 {
 	int i;
 
@@ -1527,10 +1510,10 @@  static void htab_free_malloced_timers_or_wq(struct bpf_htab *htab, bool is_timer
 
 		hlist_nulls_for_each_entry(l, n, head, hash_node) {
 			/* We only free timer on uref dropping to zero */
-			if (is_timer)
+			if (btf_record_has_field(htab->map.record, BPF_TIMER))
 				bpf_obj_free_timer(htab->map.record,
 						   l->key + round_up(htab->map.key_size, 8));
-			else
+			if (btf_record_has_field(htab->map.record, BPF_WORKQUEUE))
 				bpf_obj_free_workqueue(htab->map.record,
 						       l->key + round_up(htab->map.key_size, 8));
 		}
@@ -1544,17 +1527,11 @@  static void htab_map_free_timers_and_wq(struct bpf_map *map)
 	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 
 	/* We only free timer and workqueue on uref dropping to zero */
-	if (btf_record_has_field(htab->map.record, BPF_TIMER)) {
-		if (!htab_is_prealloc(htab))
-			htab_free_malloced_timers_or_wq(htab, true);
-		else
-			htab_free_prealloced_timers(htab);
-	}
-	if (btf_record_has_field(htab->map.record, BPF_WORKQUEUE)) {
+	if (btf_record_has_field(htab->map.record, BPF_TIMER | BPF_WORKQUEUE)) {
 		if (!htab_is_prealloc(htab))
-			htab_free_malloced_timers_or_wq(htab, false);
+			htab_free_malloced_timers_and_wq(htab);
 		else
-			htab_free_prealloced_wq(htab);
+			htab_free_prealloced_timers_and_wq(htab);
 	}
 }