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xfrm: ipcomp: remove unnecessary get_cpu() 

While testing ipcomp on a realtime kernel, Xiumei reported a "sleeping
in atomic" bug, caused by a memory allocation while preemption is
disabled (ipcomp_decompress -> alloc_page -> ... get_page_from_freelist).

As Sebastian noted [1], this get_cpu() isn't actually needed, since
ipcomp_decompress() is called in napi context anyway, so BH is already
disabled.

This patch replaces get_cpu + per_cpu_ptr with this_cpu_ptr, then
simplifies the error returns, since there isn't any common operation
left.

[1] https://lore.kernel.org/lkml/20190820082810.ixkmi56fp7u7eyn2@linutronix.de/

Cc: Juri Lelli <jlelli@redhat.com>
Reported-by: Xiumei Mu <xmu@redhat.com>
Suggested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
This commit is contained in:
Sabrina Dubroca 2021-04-16 17:11:46 +02:00 committed by Steffen Klassert
parent 6218fe1861
commit 747b67088f
1 changed files with 8 additions and 17 deletions
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25
net/xfrm/xfrm_ipcomp.c
View File

@ -41,19 +41,16 @@ 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);
u8 *scratch = *this_cpu_ptr(ipcomp_scratches);
struct crypto_comp *tfm = *this_cpu_ptr(ipcd->tfms);
int err = crypto_comp_decompress(tfm, start, plen, scratch, &dlen);
int len;
if (err)
goto out;
return err;
if (dlen < (plen + sizeof(struct ip_comp_hdr))) {
err = -EINVAL;
goto out;
}
if (dlen < (plen + sizeof(struct ip_comp_hdr)))
return -EINVAL;
len = dlen - plen;
if (len > skb_tailroom(skb))
@ -68,16 +65,14 @@ static int ipcomp_decompress(struct xfrm_state *x, struct sk_buff *skb)
skb_frag_t *frag;
struct page *page;
err = -EMSGSIZE;
if (WARN_ON(skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS))
goto out;
return -EMSGSIZE;
frag = skb_shinfo(skb)->frags + skb_shinfo(skb)->nr_frags;
page = alloc_page(GFP_ATOMIC);
err = -ENOMEM;
if (!page)
goto out;
return -ENOMEM;
__skb_frag_set_page(frag, page);
@ -96,11 +91,7 @@ static int ipcomp_decompress(struct xfrm_state *x, struct sk_buff *skb)
skb_shinfo(skb)->nr_frags++;
}
err = 0;
out:
put_cpu();
return err;
return 0;
}
int ipcomp_input(struct xfrm_state *x, struct sk_buff *skb)