From: Connor O'Brien <connoro@google.com>
Date: Wed, 23 Feb 2022 01:28:14 +0000
Subject: bpf: Add config to allow loading modules with BTF mismatches
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Git-commit: 5e214f2e43e453d862ebbbd2a4f7ee3fe650f209
Patch-mainline: v5.18-rc1
References: jsc#SLE-24559
BTF mismatch can occur for a separately-built module even when the ABI is
otherwise compatible and nothing else would prevent successfully loading.
Add a new Kconfig to control how mismatches are handled. By default, preserve
the current behavior of refusing to load the module. If MODULE_ALLOW_BTF_MISMATCH
is enabled, load the module but ignore its BTF information.
Suggested-by: Yonghong Song <yhs@fb.com>
Suggested-by: Michal Suchánek <msuchanek@suse.de>
Signed-off-by: Connor O'Brien <connoro@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/CAADnVQJ+OVPnBz8z3vNu8gKXX42jCUqfuvhWAyCQDu8N_yqqwQ@mail.gmail.com
Link: https://lore.kernel.org/bpf/20220223012814.1898677-1-connoro@google.com
Acked-by: Jeff Mahoney <jeffm@suse.com>
---
kernel/bpf/btf.c | 3 ++-
lib/Kconfig.debug | 10 ++++++++++
2 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 0890e56e8b08..b472cf0c8fdb 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6398,7 +6398,8 @@ static int btf_module_notify(struct notifier_block *nb, unsigned long op,
pr_warn("failed to validate module [%s] BTF: %ld\n",
mod->name, PTR_ERR(btf));
kfree(btf_mod);
- err = PTR_ERR(btf);
+ if (!IS_ENABLED(CONFIG_MODULE_ALLOW_BTF_MISMATCH))
+ err = PTR_ERR(btf);
goto out;
}
err = btf_alloc_id(btf);
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 1555da672275..72ca4684beda 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -339,6 +339,16 @@ config DEBUG_INFO_BTF_MODULES
help
Generate compact split BTF type information for kernel modules.
+config MODULE_ALLOW_BTF_MISMATCH
+ bool "Allow loading modules with non-matching BTF type info"
+ depends on DEBUG_INFO_BTF_MODULES
+ help
+ For modules whose split BTF does not match vmlinux, load without
+ BTF rather than refusing to load. The default behavior with
+ module BTF enabled is to reject modules with such mismatches;
+ this option will still load module BTF where possible but ignore
+ it when a mismatch is found.
+
config GDB_SCRIPTS
bool "Provide GDB scripts for kernel debugging"
depends on DEBUG_INFO