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    SubjectRe: [PATCH v3 11/12] lkdtm: Fix execute_[user]_location()
    Date
    Hi Kees,

    Le 17/10/2021 à 14:38, Christophe Leroy a écrit :
    > execute_location() and execute_user_location() intent
    > to copy do_nothing() text and execute it at a new location.
    > However, at the time being it doesn't copy do_nothing() function
    > but do_nothing() function descriptor which still points to the
    > original text. So at the end it still executes do_nothing() at
    > its original location allthough using a copied function descriptor.
    >
    > So, fix that by really copying do_nothing() text and build a new
    > function descriptor by copying do_nothing() function descriptor and
    > updating the target address with the new location.
    >
    > Also fix the displayed addresses by dereferencing do_nothing()
    > function descriptor.
    >
    > Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>

    Do you have any comment to this patch and to patch 12 ?

    If not, is it ok to get your acked-by ?

    Thanks
    Christophe

    > ---
    > drivers/misc/lkdtm/perms.c | 37 ++++++++++++++++++++++++++++---------
    > 1 file changed, 28 insertions(+), 9 deletions(-)
    >
    > diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
    > index 035fcca441f0..1cf24c4a79e9 100644
    > --- a/drivers/misc/lkdtm/perms.c
    > +++ b/drivers/misc/lkdtm/perms.c
    > @@ -44,19 +44,34 @@ static noinline void do_overwritten(void)
    > return;
    > }
    >
    > +static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
    > +{
    > + if (!have_function_descriptors())
    > + return dst;
    > +
    > + memcpy(fdesc, do_nothing, sizeof(*fdesc));
    > + fdesc->addr = (unsigned long)dst;
    > + barrier();
    > +
    > + return fdesc;
    > +}
    > +
    > static noinline void execute_location(void *dst, bool write)
    > {
    > - void (*func)(void) = dst;
    > + void (*func)(void);
    > + func_desc_t fdesc;
    > + void *do_nothing_text = dereference_function_descriptor(do_nothing);
    >
    > - pr_info("attempting ok execution at %px\n", do_nothing);
    > + pr_info("attempting ok execution at %px\n", do_nothing_text);
    > do_nothing();
    >
    > if (write == CODE_WRITE) {
    > - memcpy(dst, do_nothing, EXEC_SIZE);
    > + memcpy(dst, do_nothing_text, EXEC_SIZE);
    > flush_icache_range((unsigned long)dst,
    > (unsigned long)dst + EXEC_SIZE);
    > }
    > - pr_info("attempting bad execution at %px\n", func);
    > + pr_info("attempting bad execution at %px\n", dst);
    > + func = setup_function_descriptor(&fdesc, dst);
    > func();
    > pr_err("FAIL: func returned\n");
    > }
    > @@ -66,16 +81,19 @@ static void execute_user_location(void *dst)
    > int copied;
    >
    > /* Intentionally crossing kernel/user memory boundary. */
    > - void (*func)(void) = dst;
    > + void (*func)(void);
    > + func_desc_t fdesc;
    > + void *do_nothing_text = dereference_function_descriptor(do_nothing);
    >
    > - pr_info("attempting ok execution at %px\n", do_nothing);
    > + pr_info("attempting ok execution at %px\n", do_nothing_text);
    > do_nothing();
    >
    > - copied = access_process_vm(current, (unsigned long)dst, do_nothing,
    > + copied = access_process_vm(current, (unsigned long)dst, do_nothing_text,
    > EXEC_SIZE, FOLL_WRITE);
    > if (copied < EXEC_SIZE)
    > return;
    > - pr_info("attempting bad execution at %px\n", func);
    > + pr_info("attempting bad execution at %px\n", dst);
    > + func = setup_function_descriptor(&fdesc, dst);
    > func();
    > pr_err("FAIL: func returned\n");
    > }
    > @@ -153,7 +171,8 @@ void lkdtm_EXEC_VMALLOC(void)
    >
    > void lkdtm_EXEC_RODATA(void)
    > {
    > - execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS);
    > + execute_location(dereference_function_descriptor(lkdtm_rodata_do_nothing),
    > + CODE_AS_IS);
    > }
    >
    > void lkdtm_EXEC_USERSPACE(void)
    >
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