Messages in this thread | | | Subject | Re: [PATCH v1 09/10] lkdtm: Fix lkdtm_EXEC_RODATA() | From | Christophe Leroy <> | Date | Wed, 13 Oct 2021 09:39:34 +0200 |
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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@csgroup.eu> >> --- >> 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
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