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@xxxxxxxxx> Acked-by: David Vernet <void@xxxxxxxxxxxxx> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx> --- kernel/bpf/helpers.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index bf9a6a646254..842229671af0 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -1495,7 +1495,11 @@ 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); + /* Source and destination may possibly overlap, hence use memmove to + * copy the data. E.g. bpf_dynptr_from_mem may create two dynptr + * pointing to overlapping PTR_TO_MAP_VALUE regions. + */ + memmove(dst, src->data + src->offset + offset, len); return 0; } @@ -1523,7 +1527,11 @@ 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); + /* Source and destination may possibly overlap, hence use memmove to + * copy the data. E.g. bpf_dynptr_from_mem may create two dynptr + * pointing to overlapping PTR_TO_MAP_VALUE regions. + */ + memmove(dst->data + dst->offset + offset, src, len); return 0; } -- 2.38.1
