[PATCH bpf-next 1/2] bpf: fix bpf_prog_pack for multi-node setup

[Song Liu <song@xxxxxxxxxx>]

module_alloc requires num_online_nodes * PMD_SIZE to allocate huge pages.
bpf_prog_pack uses pack of size num_online_nodes * PMD_SIZE.
OTOH, module_alloc returns addresses that are PMD_SIZE aligned (instead of
num_online_nodes * PMD_SIZE aligned). Therefore, PMD_MASK should be used
to calculate pack_ptr in bpf_prog_pack_free().

Fixes: ef078600eec2 ("bpf: Select proper size for bpf_prog_pack")
Reported-by: syzbot+c946805b5ce6ab87df0b@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Song Liu <song@xxxxxxxxxx>
---
 kernel/bpf/core.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 9d661e07e77c..f6b20fcbeb24 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -829,6 +829,7 @@ struct bpf_prog_pack {
 #define BPF_PROG_SIZE_TO_NBITS(size)	(round_up(size, BPF_PROG_CHUNK_SIZE) / BPF_PROG_CHUNK_SIZE)
 
 static size_t bpf_prog_pack_size = -1;
+static size_t bpf_prog_pack_mask = -1;
 
 static int bpf_prog_chunk_count(void)
 {
@@ -850,8 +851,12 @@ static size_t select_bpf_prog_pack_size(void)
 	/* Test whether we can get huge pages. If not just use PAGE_SIZE
 	 * packs.
 	 */
-	if (!ptr || !is_vm_area_hugepages(ptr))
+	if (!ptr || !is_vm_area_hugepages(ptr)) {
 		size = PAGE_SIZE;
+		bpf_prog_pack_mask = PAGE_MASK;
+	} else {
+		bpf_prog_pack_mask = PMD_MASK;
+	}
 
 	vfree(ptr);
 	return size;
@@ -935,7 +940,7 @@ static void bpf_prog_pack_free(struct bpf_binary_header *hdr)
 		goto out;
 	}
 
-	pack_ptr = (void *)((unsigned long)hdr & ~(bpf_prog_pack_size - 1));
+	pack_ptr = (void *)((unsigned long)hdr & bpf_prog_pack_mask);
 
 	list_for_each_entry(tmp, &pack_list, list) {
 		if (tmp->ptr == pack_ptr) {
-- 
2.30.2