Messages in this thread |  | | Date | Wed, 3 Jun 2026 12:58:05 +0200 | | From | Steffen Klassert <> | | Subject | Re: [PATCH ipsec] esp: fix page frag reference leak on skb_to_sgvec failure |
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On Mon, Jun 01, 2026 at 03:45:25PM +0200, Alessandro Schino wrote: > In esp_output_tail(), when esp->inplace is false, the old skb page frags > are replaced with a new page from the xfrm page_frag cache. The source > scatterlist (sg) is built from the old frags before the replacement, and > esp_ssg_unref() is responsible for releasing the old page references > after the crypto operation completes. > > However, if the second skb_to_sgvec() call (which builds the destination > scatterlist from the new page) fails, the code jumps to error_free which > only calls kfree(tmp). The old page frag references captured in the > source scatterlist are never released: > > 1. sg[] is built from old frags via skb_to_sgvec() (no extra get_page) > 2. nr_frags is set to 1 and frag[0] is replaced with the new page > 3. Second skb_to_sgvec() fails -> goto error_free > > Fix this by adding a bool parameter to esp_ssg_unref() that, when true, > unconditionally unrefs the source scatterlist frags. Since req->src is > not yet initialized by aead_request_set_crypt() at the point of the > error, the source scatterlist is obtained directly via esp_req_sg(). > Existing callers pass false to preserve the original behavior. > > The same issue exists in both esp4 and esp6 as the code is identical. > > Fixes: cac2661c53f3 ("esp4: Avoid skb_cow_data whenever possible") > Fixes: 03e2a30f6a27 ("esp6: Avoid skb_cow_data whenever possible") > Signed-off-by: Alessandro Schino <7991aleschino@gmail.com> > --- > net/ipv4/esp4.c | 14 ++++++++------ > net/ipv6/esp6.c | 14 ++++++++------ > 2 files changed, 16 insertions(+), 12 deletions(-) > > diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c > index 513c8215c947..2429c7845984 100644 > --- a/net/ipv4/esp4.c > +++ b/net/ipv4/esp4.c > @@ -96,7 +96,7 @@ static inline struct scatterlist *esp_req_sg(struct crypto_aead *aead, > __alignof__(struct scatterlist)); > } > > -static void esp_ssg_unref(struct xfrm_state *x, void *tmp, struct sk_buff *skb) > +static void esp_ssg_unref(struct xfrm_state *x, void *tmp, struct sk_buff *skb, bool already_unref) > { > struct crypto_aead *aead = x->data; > int extralen = 0; > @@ -113,8 +113,8 @@ static void esp_ssg_unref(struct xfrm_state *x, void *tmp, struct sk_buff *skb) > /* Unref skb_frag_pages in the src scatterlist if necessary. > * Skip the first sg which comes from skb->data. > */ > - if (req->src != req->dst) > - for (sg = sg_next(req->src); sg; sg = sg_next(sg)) > + if (already_unref || req->src != req->dst) > + for (sg = sg_next(already_unref ? esp_req_sg(aead, req) : req->src); sg; sg = sg_next(sg)) > skb_page_unref(page_to_netmem(sg_page(sg)), > skb->pp_recycle); > } > @@ -220,7 +220,7 @@ static void esp_output_done(void *data, int err) > } > > tmp = ESP_SKB_CB(skb)->tmp; > - esp_ssg_unref(x, tmp, skb); > + esp_ssg_unref(x, tmp, skb, false); > kfree(tmp); > > if (xo && (xo->flags & XFRM_DEV_RESUME)) { > @@ -569,8 +569,10 @@ int esp_output_tail(struct xfrm_state *x, struct sk_buff *skb, struct esp_info * > err = skb_to_sgvec(skb, dsg, > (unsigned char *)esph - skb->data, > assoclen + ivlen + esp->clen + alen); > - if (unlikely(err < 0)) > + if (unlikely(err < 0)) { > + esp_ssg_unref(x, tmp, skb, true); > goto error_free; > + } > } > > if ((x->props.flags & XFRM_STATE_ESN)) > @@ -602,7 +604,7 @@ int esp_output_tail(struct xfrm_state *x, struct sk_buff *skb, struct esp_info * > } > > if (sg != dsg) > - esp_ssg_unref(x, tmp, skb); > + esp_ssg_unref(x, tmp, skb, false); > > if (!err && x->encap && x->encap->encap_type == TCP_ENCAP_ESPINTCP) > err = esp_output_tail_tcp(x, skb); > diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c > index 57481e423e59..50af6ab9b8fc 100644 > --- a/net/ipv6/esp6.c > +++ b/net/ipv6/esp6.c > @@ -113,7 +113,7 @@ static inline struct scatterlist *esp_req_sg(struct crypto_aead *aead, > __alignof__(struct scatterlist)); > } > > -static void esp_ssg_unref(struct xfrm_state *x, void *tmp, struct sk_buff *skb) > +static void esp_ssg_unref(struct xfrm_state *x, void *tmp, struct sk_buff *skb, bool already_unref) > { > struct crypto_aead *aead = x->data; > int extralen = 0; > @@ -130,8 +130,8 @@ static void esp_ssg_unref(struct xfrm_state *x, void *tmp, struct sk_buff *skb) > /* Unref skb_frag_pages in the src scatterlist if necessary. > * Skip the first sg which comes from skb->data. > */ > - if (req->src != req->dst) > - for (sg = sg_next(req->src); sg; sg = sg_next(sg)) > + if (already_unref || req->src != req->dst) > + for (sg = sg_next(already_unref ? esp_req_sg(aead, req) : req->src); sg; sg = sg_next(sg)) > skb_page_unref(page_to_netmem(sg_page(sg)), > skb->pp_recycle); > }
Now checkpatch complains about this:
WARNING: line length of 106 exceeds 100 columns #21: FILE: net/ipv4/esp4.c:117: + for (sg = sg_next(already_unref ? esp_req_sg(aead, req) : req->src); sg; sg = sg_next(sg))
WARNING: line length of 106 exceeds 100 columns #75: FILE: net/ipv6/esp6.c:134: + for (sg = sg_next(already_unref ? esp_req_sg(aead, req) : req->src); sg; sg = sg_next(sg))
This is not a big issue, but it makes the code unreadable over time.
Please check your patches before you send it.
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