Re: [RFC v3 net-next 3/5] ebpf: fix bpf_msg_pull_data
On 08/24/2018 06:02 PM, John Fastabend wrote:
On 08/17/2018 04:08 PM, Tushar Dave wrote:
Like sockmap (sk_msg), socksg also deals with struct scatterlist
therefore socksg programs can use existing bpf helper bpf_msg_pull_data
to access packet data contained in struct scatterlist. While doing some
prelimnary testing, there are couple of issues found with
bpf_msg_pull_data that are fixed in this patch.
Also, there cannot be more than MAX_SKB_FRAGS entries in sg_data
therefore any checks for sg entry more than MAX_SKB_FRAGS in
bpf_msg_pull_data() is removed.
In sockmap the scatterlist is used as a ring so the MAX_SKB_FRAGS
check is needed to keep searching through the ring when sg_start
is non-zero.
Okay.
Besides that, I also ran into issues while put_page() is invoked.
e.g.
[ 450.568723] BUG: Bad page state in process swapper/10 pfn:2021540
[ 450.575632] page:ea0080855000 count:0 mapcount:0
mapping:88103d006840 index:0x88202154 compound_mapcount: 0
[ 450.588069] flags: 0x6f80008100(slab|head)
[ 450.593033] raw: 006f80008100 dead0100 dead0200
88103d006840
[ 450.601683] raw: 88202154 80080007
[ 450.610337] page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
[ 450.617530] bad because of flags: 0x100(slab)
To avoid above issue, currently put_page() is disabled in this patch
temporarily. I am working on alternatives so that page allocated via
slab (in this case) can be freed without any issue.>
Signed-off-by: Tushar Dave
Acked-by: Sowmini Varadhan
---
net/core/filter.c | 61 +--
1 file changed, 32 insertions(+), 29 deletions(-)
diff --git a/net/core/filter.c b/net/core/filter.c
index e427c8e..cc52baa 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2316,7 +2316,7 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff *msg)
BPF_CALL_4(bpf_msg_pull_data,
struct sk_msg_buff *, msg, u32, start, u32, end, u64, flags)
{
- unsigned int len = 0, offset = 0, copy = 0;
+ unsigned int len = 0, offset = 0, copy = 0, off = 0;
struct scatterlist *sg = msg->sg_data;
int first_sg, last_sg, i, shift;
unsigned char *p, *to, *from;
@@ -2330,22 +2330,28 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff
*msg)
i = msg->sg_start;
do {
len = sg[i].length;
- offset += len;
if (start < offset + len)
break;
+ offset += len;
This looks like a generic fix unrelated to this series.
Can you send that as a bugfix?
Okay.
i++;
- if (i == MAX_SKB_FRAGS)
- i = 0;
- } while (i != msg->sg_end);
+ } while (i <= msg->sg_end);
As noted above the MAX_SKB_FRAGS check is needed because
sg_start can be non-zero and sg_end < st_start. In these
cases we need to search the entries at the start of the
array (being used as a ring).
Yup!
+ /* return error if start is out of range */
if (unlikely(start >= offset + len))
return -EINVAL;
- if (!msg->sg_copy[i] && bytes <= len)
- goto out;
+ /* return error if i is last entry in sglist and end is out of range */
+ if (msg->sg_copy[i] && end > offset + len)
+ return -EINVAL>
first_sg = i;
+ /* if i is not last entry in sg list and end (i.e start + bytes) is
+* within this sg[i] then goto out and calculate data and data_end
+*/
+ if (!msg->sg_copy[i] && end <= offset + len)
+ goto out;
+> /* At this point we need to linearize multiple scatterlist
* elements or a single shared page. Either way we need to
* copy into a linear buffer exclusively owned by BPF. Then
@@ -2359,11 +2365,14 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff
*msg)
do {
copy += sg[i].length;
i++;
- if (i == MAX_SKB_FRAGS)
- i = 0;
same as above, need to keep.
Yup!
- if (bytes < copy)
+ if (end < copy)
break;
- } while (i != msg->sg_end);
+ } while (i <= msg->sg_end);
+
+ /* return error if i is last entry in sglist and end is out of range */
+ if (i > msg->sg_end && end > offset + copy)
+ return -EINVAL;
+
last_sg = i;
if (unlikely(copy < end - start))
@@ -2373,23 +2382,25 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff
*msg)
if (unlikely(!page))
return -ENOMEM;
p = page_address(page);
- offset = 0;
i = first_sg;
do {
from = sg_virt([i]);
len = sg[i].length;
- to = p + offset;
+ to = p + off;
Not really sure if the change from offset->off is needed. Looks
like it just makes a
Re: [RFC v3 net-next 3/5] ebpf: fix bpf_msg_pull_data
On 08/17/2018 04:08 PM, Tushar Dave wrote:
> Like sockmap (sk_msg), socksg also deals with struct scatterlist
> therefore socksg programs can use existing bpf helper bpf_msg_pull_data
> to access packet data contained in struct scatterlist. While doing some
> prelimnary testing, there are couple of issues found with
> bpf_msg_pull_data that are fixed in this patch.
>
> Also, there cannot be more than MAX_SKB_FRAGS entries in sg_data
> therefore any checks for sg entry more than MAX_SKB_FRAGS in
> bpf_msg_pull_data() is removed.
In sockmap the scatterlist is used as a ring so the MAX_SKB_FRAGS
check is needed to keep searching through the ring when sg_start
is non-zero.
>
> Besides that, I also ran into issues while put_page() is invoked.
> e.g.
> [ 450.568723] BUG: Bad page state in process swapper/10 pfn:2021540
> [ 450.575632] page:ea0080855000 count:0 mapcount:0
> mapping:88103d006840 index:0x88202154 compound_mapcount: 0
> [ 450.588069] flags: 0x6f80008100(slab|head)
> [ 450.593033] raw: 006f80008100 dead0100 dead0200
> 88103d006840
> [ 450.601683] raw: 88202154 80080007
>
> [ 450.610337] page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
> [ 450.617530] bad because of flags: 0x100(slab)
>
> To avoid above issue, currently put_page() is disabled in this patch
> temporarily. I am working on alternatives so that page allocated via
> slab (in this case) can be freed without any issue.>
> Signed-off-by: Tushar Dave
> Acked-by: Sowmini Varadhan
> ---
> net/core/filter.c | 61
> +--
> 1 file changed, 32 insertions(+), 29 deletions(-)
>
> diff --git a/net/core/filter.c b/net/core/filter.c
> index e427c8e..cc52baa 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -2316,7 +2316,7 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff
> *msg)
> BPF_CALL_4(bpf_msg_pull_data,
> struct sk_msg_buff *, msg, u32, start, u32, end, u64, flags)
> {
> - unsigned int len = 0, offset = 0, copy = 0;
> + unsigned int len = 0, offset = 0, copy = 0, off = 0;
> struct scatterlist *sg = msg->sg_data;
> int first_sg, last_sg, i, shift;
> unsigned char *p, *to, *from;
> @@ -2330,22 +2330,28 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff
> *msg)
> i = msg->sg_start;
> do {
> len = sg[i].length;
> - offset += len;
> if (start < offset + len)
> break;
> + offset += len;
This looks like a generic fix unrelated to this series.
Can you send that as a bugfix?
> i++;
> - if (i == MAX_SKB_FRAGS)
> - i = 0;
> - } while (i != msg->sg_end);
> + } while (i <= msg->sg_end);
>
As noted above the MAX_SKB_FRAGS check is needed because
sg_start can be non-zero and sg_end < st_start. In these
cases we need to search the entries at the start of the
array (being used as a ring).
> + /* return error if start is out of range */
> if (unlikely(start >= offset + len))
> return -EINVAL;
>
> - if (!msg->sg_copy[i] && bytes <= len)
> - goto out;
> + /* return error if i is last entry in sglist and end is out of range */
> + if (msg->sg_copy[i] && end > offset + len)
> + return -EINVAL>
> first_sg = i;
>
> + /* if i is not last entry in sg list and end (i.e start + bytes) is
> + * within this sg[i] then goto out and calculate data and data_end
> + */
> + if (!msg->sg_copy[i] && end <= offset + len)
> + goto out;
> +>/* At this point we need to linearize multiple scatterlist
>* elements or a single shared page. Either way we need to
>* copy into a linear buffer exclusively owned by BPF. Then
> @@ -2359,11 +2365,14 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff
> *msg)
> do {
> copy += sg[i].length;
> i++;
> - if (i == MAX_SKB_FRAGS)
> - i = 0;
same as above, need to keep.
> - if (bytes < copy)
> + if (end < copy)
> break;
> - } while (i != msg->sg_end);
> + } while (i <= msg->sg_end);
> +
> + /* return error if i is last entry in sglist and end is out of range */
> + if (i > msg->sg_end && end > offset + copy)
> + return -EINVAL;
> +
> last_sg = i;
>
> if (unlikely(copy < end - start))
> @@ -2373,23 +2382,25 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff
> *msg)
> if (unlikely(!page))
> return -ENOMEM;
> p = page_address(page);
> - offset = 0;
>
> i = first_sg;
> do {
> from = sg_virt([i]);
> len = sg[i].length;
> - to = p + offset;
> + to = p + off;
Not really sure if the change from offset->off is needed.
[RFC v3 net-next 3/5] ebpf: fix bpf_msg_pull_data
Like sockmap (sk_msg), socksg also deals with struct scatterlist
therefore socksg programs can use existing bpf helper bpf_msg_pull_data
to access packet data contained in struct scatterlist. While doing some
prelimnary testing, there are couple of issues found with
bpf_msg_pull_data that are fixed in this patch.
Also, there cannot be more than MAX_SKB_FRAGS entries in sg_data
therefore any checks for sg entry more than MAX_SKB_FRAGS in
bpf_msg_pull_data() is removed.
Besides that, I also ran into issues while put_page() is invoked.
e.g.
[ 450.568723] BUG: Bad page state in process swapper/10 pfn:2021540
[ 450.575632] page:ea0080855000 count:0 mapcount:0
mapping:88103d006840 index:0x88202154 compound_mapcount: 0
[ 450.588069] flags: 0x6f80008100(slab|head)
[ 450.593033] raw: 006f80008100 dead0100 dead0200
88103d006840
[ 450.601683] raw: 88202154 80080007
[ 450.610337] page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
[ 450.617530] bad because of flags: 0x100(slab)
To avoid above issue, currently put_page() is disabled in this patch
temporarily. I am working on alternatives so that page allocated via
slab (in this case) can be freed without any issue.
Signed-off-by: Tushar Dave
Acked-by: Sowmini Varadhan
---
net/core/filter.c | 61 +--
1 file changed, 32 insertions(+), 29 deletions(-)
diff --git a/net/core/filter.c b/net/core/filter.c
index e427c8e..cc52baa 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2316,7 +2316,7 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff *msg)
BPF_CALL_4(bpf_msg_pull_data,
struct sk_msg_buff *, msg, u32, start, u32, end, u64, flags)
{
- unsigned int len = 0, offset = 0, copy = 0;
+ unsigned int len = 0, offset = 0, copy = 0, off = 0;
struct scatterlist *sg = msg->sg_data;
int first_sg, last_sg, i, shift;
unsigned char *p, *to, *from;
@@ -2330,22 +2330,28 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff
*msg)
i = msg->sg_start;
do {
len = sg[i].length;
- offset += len;
if (start < offset + len)
break;
+ offset += len;
i++;
- if (i == MAX_SKB_FRAGS)
- i = 0;
- } while (i != msg->sg_end);
+ } while (i <= msg->sg_end);
+ /* return error if start is out of range */
if (unlikely(start >= offset + len))
return -EINVAL;
- if (!msg->sg_copy[i] && bytes <= len)
- goto out;
+ /* return error if i is last entry in sglist and end is out of range */
+ if (msg->sg_copy[i] && end > offset + len)
+ return -EINVAL;
first_sg = i;
+ /* if i is not last entry in sg list and end (i.e start + bytes) is
+* within this sg[i] then goto out and calculate data and data_end
+*/
+ if (!msg->sg_copy[i] && end <= offset + len)
+ goto out;
+
/* At this point we need to linearize multiple scatterlist
* elements or a single shared page. Either way we need to
* copy into a linear buffer exclusively owned by BPF. Then
@@ -2359,11 +2365,14 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff
*msg)
do {
copy += sg[i].length;
i++;
- if (i == MAX_SKB_FRAGS)
- i = 0;
- if (bytes < copy)
+ if (end < copy)
break;
- } while (i != msg->sg_end);
+ } while (i <= msg->sg_end);
+
+ /* return error if i is last entry in sglist and end is out of range */
+ if (i > msg->sg_end && end > offset + copy)
+ return -EINVAL;
+
last_sg = i;
if (unlikely(copy < end - start))
@@ -2373,23 +2382,25 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff
*msg)
if (unlikely(!page))
return -ENOMEM;
p = page_address(page);
- offset = 0;
i = first_sg;
do {
from = sg_virt([i]);
len = sg[i].length;
- to = p + offset;
+ to = p + off;
memcpy(to, from, len);
- offset += len;
+ off += len;
sg[i].length = 0;
- put_page(sg_page([i]));
+ /* if original page is allocated via slab then put_page
+* causes error BUG: Bad page state in process. So temporarily
+* disabled put_page.
+* Todo: fix it
+*/
+ //put_page(sg_page([i]));
i++;
- if (i == MAX_SKB_FRAGS)
- i = 0;
- } while (i != last_sg);
+ } while (i < last_sg);
sg[first_sg].length = copy;
