bpf: relax inode permission check for retrieving bpf program

For iptable module to load a bpf program from a pinned location, it
only retrieve a loaded program and cannot change the program content so
requiring a write permission for it might not be necessary.
Also when adding or removing an unrelated iptable rule, it might need to
flush and reload the xt_bpf related rules as well and triggers the inode
permission check. It might be better to remove the write premission
check for the inode so we won't need to grant write access to all the
processes that flush and restore iptables rules.

Signed-off-by: Chenbo Feng <fengc@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index bc53e5b20ddc7d991de8db58ec3576bbcc381b14..84a80b02db994c7bcc125ec28c4fa831ac582724 100644 (file)
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -518,7 +518,7 @@ out:
 static struct bpf_prog *__get_prog_inode(struct inode *inode, enum bpf_prog_type type)
 {
        struct bpf_prog *prog;
-       int ret = inode_permission(inode, MAY_READ | MAY_WRITE);
+       int ret = inode_permission(inode, MAY_READ);
        if (ret)
                return ERR_PTR(ret);