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cfi: Switch to -fsanitize=kcfi

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Switch from Clang's original forward-edge control-flow integrity
implementation to -fsanitize=kcfi, which is better suited for the
kernel, as it doesn't require LTO, doesn't use a jump table that
requires altering function references, and won't break cross-module
function address equality.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Kees Cook <keescook@chromium.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220908215504.3686827-6-samitolvanen@google.com
This commit is contained in:
Sami Tolvanen
2022-09-08 14:54:47 -07:00
committed by Kees Cook
parent 92efda8eb1
commit 8924560094
9 changed files with 139 additions and 182 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/module/main.c
+3 -32
View File
@@ -53,6 +53,7 @@
#include <linux/bsearch.h>
#include <linux/dynamic_debug.h>
#include <linux/audit.h>
#include <linux/cfi.h>
#include <uapi/linux/module.h>
#include "internal.h"
@@ -2597,8 +2598,9 @@ static int complete_formation(struct module *mod, struct load_info *info)
if (err < 0)
goto out;
/* This relies on module_mutex for list integrity. */
/* These rely on module_mutex for list integrity. */
module_bug_finalize(info->hdr, info->sechdrs, mod);
module_cfi_finalize(info->hdr, info->sechdrs, mod);
if (module_check_misalignment(mod))
goto out_misaligned;
@@ -2660,8 +2662,6 @@ static int unknown_module_param_cb(char *param, char *val, const char *modname,
return 0;
}
static void cfi_init(struct module *mod);
/*
* Allocate and load the module: note that size of section 0 is always
* zero, and we rely on this for optional sections.
@@ -2791,9 +2791,6 @@ static int load_module(struct load_info *info, const char __user *uargs,
flush_module_icache(mod);
/* Setup CFI for the module. */
cfi_init(mod);
/* Now copy in args */
mod->args = strndup_user(uargs, ~0UL >> 1);
if (IS_ERR(mod->args)) {
@@ -2955,32 +2952,6 @@ static inline int within(unsigned long addr, void *start, unsigned long size)
return ((void *)addr >= start && (void *)addr < start + size);
}
static void cfi_init(struct module *mod)
{
#ifdef CONFIG_CFI_CLANG
initcall_t *init;
#ifdef CONFIG_MODULE_UNLOAD
exitcall_t *exit;
#endif
rcu_read_lock_sched();
mod->cfi_check = (cfi_check_fn)
find_kallsyms_symbol_value(mod, "__cfi_check");
init = (initcall_t *)
find_kallsyms_symbol_value(mod, "__cfi_jt_init_module");
/* Fix init/exit functions to point to the CFI jump table */
if (init)
mod->init = *init;
#ifdef CONFIG_MODULE_UNLOAD
exit = (exitcall_t *)
find_kallsyms_symbol_value(mod, "__cfi_jt_cleanup_module");
if (exit)
mod->exit = *exit;
#endif
rcu_read_unlock_sched();
#endif
}
/* Keep in sync with MODULE_FLAGS_BUF_SIZE !!! */
char *module_flags(struct module *mod, char *buf, bool show_state)
{