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Date: Tue, 15 Oct 2013 23:40:30 +0200 (CEST) From: Michal Kubecek <mkubecek@...e.cz> To: Steffen Klassert <steffen.klassert@...unet.com> Cc: Herbert Xu <herbert@...dor.apana.org.au>, "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org Subject: [PATCH ipsec v2] xfrm: prevent ipcomp scratch buffer race condition In ipcomp_compress(), sortirq is enabled too early, allowing the per-cpu scratch buffer to be rewritten by ipcomp_decompress() (called on the same CPU in softirq context) between populating the buffer and copying the compressed data to the skb. Add similar protection into ipcomp_decompress() as it can be called from process context as well (even if such scenario seems a bit artificial). v2: as pointed out by Steffen Klassert, if we also move the local_bh_disable() before reading the per-cpu pointers, we can get rid of get_cpu()/put_cpu(). Signed-off-by: Michal Kubecek <mkubecek@...e.cz> --- net/xfrm/xfrm_ipcomp.c | 29 ++++++++++++++++++----------- 1 file changed, 18 insertions(+), 11 deletions(-) diff --git a/net/xfrm/xfrm_ipcomp.c b/net/xfrm/xfrm_ipcomp.c index 2906d52..9fe4f42 100644 --- a/net/xfrm/xfrm_ipcomp.c +++ b/net/xfrm/xfrm_ipcomp.c @@ -45,12 +45,17 @@ static int ipcomp_decompress(struct xfrm_state *x, struct sk_buff *skb) const int plen = skb->len; int dlen = IPCOMP_SCRATCH_SIZE; const u8 *start = skb->data; - const int cpu = get_cpu(); - u8 *scratch = *per_cpu_ptr(ipcomp_scratches, cpu); - struct crypto_comp *tfm = *per_cpu_ptr(ipcd->tfms, cpu); - int err = crypto_comp_decompress(tfm, start, plen, scratch, &dlen); + struct crypto_comp *tfm; + u8 *scratch; + int cpu; + int err; int len; + local_bh_disable(); + cpu = smp_processor_id(); + scratch = *per_cpu_ptr(ipcomp_scratches, cpu); + tfm = *per_cpu_ptr(ipcd->tfms, cpu); + err = crypto_comp_decompress(tfm, start, plen, scratch, &dlen); if (err) goto out; @@ -103,7 +108,7 @@ static int ipcomp_decompress(struct xfrm_state *x, struct sk_buff *skb) err = 0; out: - put_cpu(); + local_bh_enable(); return err; } @@ -141,14 +146,16 @@ static int ipcomp_compress(struct xfrm_state *x, struct sk_buff *skb) const int plen = skb->len; int dlen = IPCOMP_SCRATCH_SIZE; u8 *start = skb->data; - const int cpu = get_cpu(); - u8 *scratch = *per_cpu_ptr(ipcomp_scratches, cpu); - struct crypto_comp *tfm = *per_cpu_ptr(ipcd->tfms, cpu); + struct crypto_comp *tfm; + u8 *scratch; + int cpu; int err; local_bh_disable(); + cpu = smp_processor_id(); + scratch = *per_cpu_ptr(ipcomp_scratches, cpu); + tfm = *per_cpu_ptr(ipcd->tfms, cpu); err = crypto_comp_compress(tfm, start, plen, scratch, &dlen); - local_bh_enable(); if (err) goto out; @@ -158,13 +165,13 @@ static int ipcomp_compress(struct xfrm_state *x, struct sk_buff *skb) } memcpy(start + sizeof(struct ip_comp_hdr), scratch, dlen); - put_cpu(); + local_bh_enable(); pskb_trim(skb, dlen + sizeof(struct ip_comp_hdr)); return 0; out: - put_cpu(); + local_bh_enable(); return err; } -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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