Commit 807ae7da authored by Daniel Borkmann's avatar Daniel Borkmann
Browse files

Merge branch 'bpf-sockmap-sg-api-fixes' 



Prashant Bhole says:

====================
These patches fix sg api usage in sockmap. Previously sockmap didn't
use sg_init_table(), which caused hitting BUG_ON in sg api, when
CONFIG_DEBUG_SG is enabled

v1: added sg_init_table() calls wherever needed.

v2:
- Patch1 adds new helper function in sg api. sg_init_marker()
- Patch2 sg_init_marker() and sg_init_table() in appropriate places

Backgroud:
While reviewing v1, John Fastabend raised a valid point about
unnecessary memset in sg_init_table() because sockmap uses sg table
which embedded in a struct. As enclosing struct is zeroed out, there
is unnecessary memset in sg_init_table.

So Daniel Borkmann suggested to define another static inline function
in scatterlist.h which only initializes sg_magic. Also this function
will be called from sg_init_table. From this suggestion I defined a
function sg_init_marker() which sets sg_magic and calls sg_mark_end()
====================

Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parents 1379ef82 6ef6d84c

include/linux/scatterlist.h

+18 −0
Original line number Diff line number Diff line
@@ -248,6 +248,24 @@ static inline void *sg_virt(struct scatterlist *sg) 
	return page_address(sg_page(sg)) + sg->offset;

}



/**

 * sg_init_marker - Initialize markers in sg table

 * @sgl:	   The SG table

 * @nents:	   Number of entries in table

 *

 **/

static inline void sg_init_marker(struct scatterlist *sgl,

				  unsigned int nents)

{

#ifdef CONFIG_DEBUG_SG

	unsigned int i;



	for (i = 0; i < nents; i++)

		sgl[i].sg_magic = SG_MAGIC;

#endif

	sg_mark_end(&sgl[nents - 1]);

}



int sg_nents(struct scatterlist *sg);

int sg_nents_for_len(struct scatterlist *sg, u64 len);

struct scatterlist *sg_next(struct scatterlist *);

kernel/bpf/sockmap.c

+8 −5
Original line number Diff line number Diff line
@@ -341,7 +341,7 @@ retry: 
			md->sg_start++;

			if (md->sg_start == MAX_SKB_FRAGS)

				md->sg_start = 0;

			memset(sg, 0, sizeof(*sg));

			sg_init_table(sg, 1);



			if (md->sg_start == md->sg_end)

				break;
@@ -843,7 +843,7 @@ static int bpf_tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size) 
	}



	sg = md.sg_data;

	sg_init_table(sg, MAX_SKB_FRAGS);

	sg_init_marker(sg, MAX_SKB_FRAGS);

	rcu_read_unlock();



	lock_sock(sk);
@@ -950,10 +950,14 @@ static int bpf_tcp_sendpage(struct sock *sk, struct page *page, 


	lock_sock(sk);



	if (psock->cork_bytes)

	if (psock->cork_bytes) {

		m = psock->cork;

	else

		sg = &m->sg_data[m->sg_end];

	} else {

		m = &md;

		sg = m->sg_data;

		sg_init_marker(sg, MAX_SKB_FRAGS);

	}



	/* Catch case where ring is full and sendpage is stalled. */

	if (unlikely(m->sg_end == m->sg_start &&
@@ -961,7 +965,6 @@ static int bpf_tcp_sendpage(struct sock *sk, struct page *page, 
		goto out_err;



	psock->sg_size += size;

	sg = &m->sg_data[m->sg_end];

	sg_set_page(sg, page, size, offset);

	get_page(page);

	m->sg_copy[m->sg_end] = true;

lib/scatterlist.c

+1 −8
Original line number Diff line number Diff line
@@ -132,14 +132,7 @@ EXPORT_SYMBOL(sg_last); 
void sg_init_table(struct scatterlist *sgl, unsigned int nents)

{

	memset(sgl, 0, sizeof(*sgl) * nents);

#ifdef CONFIG_DEBUG_SG

	{

		unsigned int i;

		for (i = 0; i < nents; i++)

			sgl[i].sg_magic = SG_MAGIC;

	}

#endif

	sg_mark_end(&sgl[nents - 1]);

	sg_init_marker(sgl, nents);

}

EXPORT_SYMBOL(sg_init_table);

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