[PATCH bpf-next v1 6/7] bpf: Use memmove for bpf_dynptr_{read,write}

[Kumar Kartikeya Dwivedi <memxor@gmail.com>]

It may happen that destination buffer memory overlaps with memory dynptr
points to. Hence, we must use memmove to correctly copy from dynptr to
destination buffer, or source buffer to dynptr.

This actually isn't a problem right now, as memcpy implementation falls
back to memmove on detecting overlap and warns about it, but we
shouldn't be relying on that.

Acked-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/helpers.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 714f5c9d0c1f..1099ed1e7712 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1489,7 +1489,7 @@ BPF_CALL_5(bpf_dynptr_read, void *, dst, u32, len, const struct bpf_dynptr_kern
 	if (err)
 		return err;
 
-	memcpy(dst, src->data + src->offset + offset, len);
+	memmove(dst, src->data + src->offset + offset, len);
 
 	return 0;
 }
@@ -1517,7 +1517,7 @@ BPF_CALL_5(bpf_dynptr_write, const struct bpf_dynptr_kern *, dst, u32, offset, v
 	if (err)
 		return err;
 
-	memcpy(dst->data + dst->offset + offset, src, len);
+	memmove(dst->data + dst->offset + offset, src, len);
 
 	return 0;
 }
-- 
2.38.1