| Message ID | 20210513114808.120031-3-xuanzhuo@linux.alibaba.com (mailing list archive) |
|---|---|
| State | Superseded |
| Commit | 7bf64460e3b2af4e6e46d932b2fbd933d662d19f |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | virtio-net: fix for build_skb() | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for net-next |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | warning | 5 maintainers not CCed: yhs@fb.com kpsingh@kernel.org andrii@kernel.org kafai@fb.com songliubraving@fb.com |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 14 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 3e46c12dde08..073fec4c0df1 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -407,8 +407,12 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi, * see add_recvbuf_mergeable() + get_mergeable_buf_len() */ truesize = PAGE_SIZE; - tailroom = truesize - len - offset; - buf = page_address(page); + + /* page maybe head page, so we should get the buf by p, not the + * page + */ + tailroom = truesize - len - offset_in_page(p); + buf = (char *)((unsigned long)p & PAGE_MASK); } else { tailroom = truesize - len; buf = p;
In the case of merge, the page passed into page_to_skb() may be a head page, not the page where the current data is located. So when trying to get the buf where the data is located, you should directly use the pointer(p) to get the address corresponding to the page. At the same time, the offset of the data in the page should also be obtained using offset_in_page(). This patch solves this problem. But if you don’t use this patch, the original code can also run, because if the page is not the page of the current data, the calculated tailroom will be less than 0, and will not enter the logic of build_skb() . The significance of this patch is to modify this logical problem, allowing more situations to use build_skb(). Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> --- drivers/net/virtio_net.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)