Le 13/10/2021 à 09:23, Kees Cook a écrit :
On Mon, Oct 11, 2021 at 05:25:36PM +0200, Christophe Leroy wrote:Behind a location, lkdtm_EXEC_RODATA() executes a real function, not a copy of do_nothing(). So do it directly instead of using execute_location(). And fix displayed addresses by dereferencing the function descriptors. Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx> --- drivers/misc/lkdtm/perms.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c index 442d60ed25ef..da16564e1ecd 100644 --- a/drivers/misc/lkdtm/perms.c +++ b/drivers/misc/lkdtm/perms.c @@ -153,7 +153,14 @@ void lkdtm_EXEC_VMALLOC(void) void lkdtm_EXEC_RODATA(void) { - execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS); + pr_info("attempting ok execution at %px\n", + dereference_symbol_descriptor(do_nothing)); + do_nothing(); + + pr_info("attempting bad execution at %px\n", + dereference_symbol_descriptor(lkdtm_rodata_do_nothing)); + lkdtm_rodata_do_nothing(); + pr_err("FAIL: func returned\n"); }(In re-reading this more carefully, I see now why kallsyms.h is used earlier: _function_ vs _symbol_ descriptor.) In the next patch: static noinline void execute_location(void *dst, bool write) { ... func = setup_function_descriptor(&fdesc, dst); if (IS_ERR(func)) return; pr_info("attempting bad execution at %px\n", dst); func(); pr_err("FAIL: func returned\n"); } What are the conditions for which dereference_symbol_descriptor works but dereference _function_descriptor doesn't?
When LKDTM is built as a module I guess ? Christophe
