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Revert "net: mirror skb frag ref/unref helpers" 

This reverts commit a580ea994f.

This revert is to resolve Dragos's report of page_pool leak here:
https://lore.kernel.org/lkml/20240424165646.1625690-2-dtatulea@nvidia.com/

The reverted patch interacts very badly with commit 2cc3aeb5ec ("skbuff:
Fix a potential race while recycling page_pool packets"). The reverted
commit hopes that the pp_recycle + is_pp_page variables do not change
between the skb_frag_ref and skb_frag_unref operation. If such a change
occurs, the skb_frag_ref/unref will not operate on the same reference type.
In the case of Dragos's report, the grabbed ref was a pp ref, but the unref
was a page ref, because the pp_recycle setting on the skb was changed.

Attempting to fix this issue on the fly is risky. Lets revert and I hope
to reland this with better understanding and testing to ensure we don't
regress some edge case while streamlining skb reffing.

Fixes: a580ea994f ("net: mirror skb frag ref/unref helpers")
Reported-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Mina Almasry <almasrymina@google.com>
Link: https://lore.kernel.org/r/20240502175423.2456544-1-almasrymina@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Mina Almasry 2024-05-02 10:54:22 -07:00 committed by Jakub Kicinski
parent 5bfadc5737
commit 173e7622cc
6 changed files with 51 additions and 44 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.c
View File

@ -1659,7 +1659,7 @@ static void chcr_ktls_copy_record_in_skb(struct sk_buff *nskb,
for (i = 0; i < record->num_frags; i++) {
skb_shinfo(nskb)->frags[i] = record->frags[i];
/* increase the frag ref count */
__skb_frag_ref(&skb_shinfo(nskb)->frags[i], nskb->pp_recycle);
__skb_frag_ref(&skb_shinfo(nskb)->frags[i]);
}
skb_shinfo(nskb)->nr_frags = record->num_frags;

4
drivers/net/ethernet/sun/cassini.c
View File

@ -2000,7 +2000,7 @@ static int cas_rx_process_pkt(struct cas *cp, struct cas_rx_comp *rxc,
skb->len += hlen - swivel;
skb_frag_fill_page_desc(frag, page->buffer, off, hlen - swivel);
__skb_frag_ref(frag, skb->pp_recycle);
__skb_frag_ref(frag);
/* any more data? */
if ((words[0] & RX_COMP1_SPLIT_PKT) && ((dlen -= hlen) > 0)) {
@ -2024,7 +2024,7 @@ static int cas_rx_process_pkt(struct cas *cp, struct cas_rx_comp *rxc,
frag++;
skb_frag_fill_page_desc(frag, page->buffer, 0, hlen);
__skb_frag_ref(frag, skb->pp_recycle);
__skb_frag_ref(frag);
RX_USED_ADD(page, hlen + cp->crc_size);
}

2
drivers/net/veth.c
View File

@ -717,7 +717,7 @@ static void veth_xdp_get(struct xdp_buff *xdp)
return;
for (i = 0; i < sinfo->nr_frags; i++)
__skb_frag_ref(&sinfo->frags[i], false);
__skb_frag_ref(&sinfo->frags[i]);
}
static int veth_convert_skb_to_xdp_buff(struct veth_rq *rq,

39
include/linux/skbuff_ref.h
View File

@ -8,47 +8,16 @@
#define _LINUX_SKBUFF_REF_H
#include <linux/skbuff.h>
#include <net/page_pool/helpers.h>
#ifdef CONFIG_PAGE_POOL
static inline bool is_pp_page(struct page *page)
{
return (page->pp_magic & ~0x3UL) == PP_SIGNATURE;
}
static inline bool napi_pp_get_page(struct page *page)
{
page = compound_head(page);
if (!is_pp_page(page))
return false;
page_pool_ref_page(page);
return true;
}
#endif
static inline void skb_page_ref(struct page *page, bool recycle)
{
#ifdef CONFIG_PAGE_POOL
if (recycle && napi_pp_get_page(page))
return;
#endif
get_page(page);
}
/**
* __skb_frag_ref - take an addition reference on a paged fragment.
* @frag: the paged fragment
* @recycle: skb->pp_recycle param of the parent skb. False if no parent skb.
*
* Takes an additional reference on the paged fragment @frag. Obtains the
* correct reference count depending on whether skb->pp_recycle is set and
* whether the frag is a page pool frag.
* Takes an additional reference on the paged fragment @frag.
*/
static inline void __skb_frag_ref(skb_frag_t *frag, bool recycle)
static inline void __skb_frag_ref(skb_frag_t *frag)
{
skb_page_ref(skb_frag_page(frag), recycle);
get_page(skb_frag_page(frag));
}
/**
@ -60,7 +29,7 @@ static inline void __skb_frag_ref(skb_frag_t *frag, bool recycle)
*/
static inline void skb_frag_ref(struct sk_buff *skb, int f)
{
__skb_frag_ref(&skb_shinfo(skb)->frags[f], skb->pp_recycle);
__skb_frag_ref(&skb_shinfo(skb)->frags[f]);
}
bool napi_pp_put_page(struct page *page);

46
net/core/skbuff.c
View File

@ -904,6 +904,11 @@ static void skb_clone_fraglist(struct sk_buff *skb)
skb_get(list);
}
static bool is_pp_page(struct page *page)
{
return (page->pp_magic & ~0x3UL) == PP_SIGNATURE;
}
int skb_pp_cow_data(struct page_pool *pool, struct sk_buff **pskb,
unsigned int headroom)
{
@ -1025,6 +1030,37 @@ static bool skb_pp_recycle(struct sk_buff *skb, void *data)
return napi_pp_put_page(virt_to_page(data));
}
/**
* skb_pp_frag_ref() - Increase fragment references of a page pool aware skb
* @skb: page pool aware skb
*
* Increase the fragment reference count (pp_ref_count) of a skb. This is
* intended to gain fragment references only for page pool aware skbs,
* i.e. when skb->pp_recycle is true, and not for fragments in a
* non-pp-recycling skb. It has a fallback to increase references on normal
* pages, as page pool aware skbs may also have normal page fragments.
*/
static int skb_pp_frag_ref(struct sk_buff *skb)
{
struct skb_shared_info *shinfo;
struct page *head_page;
int i;
if (!skb->pp_recycle)
return -EINVAL;
shinfo = skb_shinfo(skb);
for (i = 0; i < shinfo->nr_frags; i++) {
head_page = compound_head(skb_frag_page(&shinfo->frags[i]));
if (likely(is_pp_page(head_page)))
page_pool_ref_page(head_page);
else
page_ref_inc(head_page);
}
return 0;
}
static void skb_kfree_head(void *head, unsigned int end_offset)
{
if (end_offset == SKB_SMALL_HEAD_HEADROOM)
@ -4160,7 +4196,7 @@ int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen)
to++;
} else {
__skb_frag_ref(fragfrom, skb->pp_recycle);
__skb_frag_ref(fragfrom);
skb_frag_page_copy(fragto, fragfrom);
skb_frag_off_copy(fragto, fragfrom);
skb_frag_size_set(fragto, todo);
@ -4810,7 +4846,7 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
}
*nskb_frag = (i < 0) ? skb_head_frag_to_page_desc(frag_skb) : *frag;
__skb_frag_ref(nskb_frag, nskb->pp_recycle);
__skb_frag_ref(nskb_frag);
size = skb_frag_size(nskb_frag);
if (pos < offset) {
@ -5941,8 +5977,10 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
/* if the skb is not cloned this does nothing
* since we set nr_frags to 0.
*/
for (i = 0; i < from_shinfo->nr_frags; i++)
__skb_frag_ref(&from_shinfo->frags[i], from->pp_recycle);
if (skb_pp_frag_ref(from)) {
for (i = 0; i < from_shinfo->nr_frags; i++)
__skb_frag_ref(&from_shinfo->frags[i]);
}
to->truesize += delta;
to->len += len;

2
net/tls/tls_device_fallback.c
View File

@ -278,7 +278,7 @@ static int fill_sg_in(struct scatterlist *sg_in,
for (i = 0; remaining > 0; i++) {
skb_frag_t *frag = &record->frags[i];
__skb_frag_ref(frag, false);
__skb_frag_ref(frag);
sg_set_page(sg_in + i, skb_frag_page(frag),
skb_frag_size(frag), skb_frag_off(frag));