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bpf: skmsg, replace comments with BUILD bug

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Enforce comment on structure layout dependency with a BUILD_BUG_ON
to ensure the condition is maintained.

Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
John Fastabend 2018-12-20 11:35:31 -08:00 committed by Daniel Borkmann
parent bc1b4f013b
commit 7a69c0f250
2 changed files with 4 additions and 3 deletions
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4
include/linux/skmsg.h
View File

@ -36,9 +36,7 @@ struct sk_msg_sg {
struct scatterlist data[MAX_MSG_FRAGS + 1]; struct scatterlist data[MAX_MSG_FRAGS + 1];
}; };
/* UAPI in filter.c depends on struct sk_msg_sg being first element. If /* UAPI in filter.c depends on struct sk_msg_sg being first element. */
* this is moved filter.c also must be updated.
*/
struct sk_msg { struct sk_msg {
struct sk_msg_sg sg; struct sk_msg_sg sg;
void *data; void *data;

3
net/core/filter.c
View File

@ -7425,6 +7425,9 @@ static u32 sk_msg_convert_ctx_access(enum bpf_access_type type,
int off; int off;
#endif #endif
/* convert ctx uses the fact sg element is first in struct */
BUILD_BUG_ON(offsetof(struct sk_msg, sg) != 0);
switch (si->off) { switch (si->off) {
case offsetof(struct sk_msg_md, data): case offsetof(struct sk_msg_md, data):
*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_msg, data), *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_msg, data),