Le 13/10/2021 à 09:09, 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().I don't understand this. Why does the next patch not fix this?
Well, probably it would, but it looked incorrect in my mind.lkdtm_rodata_do_nothing() is a function which has its own function descriptor, it is not a copy of do_nothing().
If we use execute_location() as modified by next patch, then we will execute it using the function descriptor of do_nothing(). Allthough it most likely works (at least on powerpc as it uses the same TOC) it looks odd to me to do so.
Am I missing something ? Christophe
-KeesAnd 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"); }void lkdtm_EXEC_USERSPACE(void)-- 2.31.1
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