| Message ID | 624940395e5d81967246f911a65740b9a15b5a70.1633964380.git.christophe.leroy@csgroup.eu (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Fix LKDTM for PPC64/IA64/PARISC | expand |
On Mon, Oct 11, 2021 at 05:25:35PM +0200, Christophe Leroy wrote: > WRITE_KERN is supposed to overwrite some kernel text, namely > do_overwritten() function. > > But at the time being it overwrites do_overwritten() function > descriptor, not function text. > > Fix it by dereferencing the function descriptor to obtain > function text pointer. > > And make do_overwritten() noinline so that it is really > do_overwritten() which is called by lkdtm_WRITE_KERN(). > > Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> > --- > drivers/misc/lkdtm/perms.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c > index 60b3b2fe929d..442d60ed25ef 100644 > --- a/drivers/misc/lkdtm/perms.c > +++ b/drivers/misc/lkdtm/perms.c > @@ -5,6 +5,7 @@ > * even non-readable regions. > */ > #include "lkdtm.h" > +#include <linux/kallsyms.h> Why not #include <asm/sections.h> instead here? > #include <linux/slab.h> > #include <linux/vmalloc.h> > #include <linux/mman.h> > @@ -37,7 +38,7 @@ static noinline void do_nothing(void) > } > > /* Must immediately follow do_nothing for size calculuations to work out. */ > -static void do_overwritten(void) > +static noinline void do_overwritten(void) > { > pr_info("do_overwritten wasn't overwritten!\n"); > return; > @@ -113,8 +114,9 @@ void lkdtm_WRITE_KERN(void) > size_t size; > volatile unsigned char *ptr; > > - size = (unsigned long)do_overwritten - (unsigned long)do_nothing; > - ptr = (unsigned char *)do_overwritten; > + size = (unsigned long)dereference_symbol_descriptor(do_overwritten) - > + (unsigned long)dereference_symbol_descriptor(do_nothing); > + ptr = dereference_symbol_descriptor(do_overwritten); But otherwise, yup, I expect there will be a bunch of things like this to clean up in LKDTM. :| Sorry about that! Acked-by: Kees Cook <keescook@chromium.org> > > pr_info("attempting bad %zu byte write at %px\n", size, ptr); > memcpy((void *)ptr, (unsigned char *)do_nothing, size); > -- > 2.31.1 >
Le 13/10/2021 à 09:05, Kees Cook a écrit : > On Mon, Oct 11, 2021 at 05:25:35PM +0200, Christophe Leroy wrote: >> WRITE_KERN is supposed to overwrite some kernel text, namely >> do_overwritten() function. >> >> But at the time being it overwrites do_overwritten() function >> descriptor, not function text. >> >> Fix it by dereferencing the function descriptor to obtain >> function text pointer. >> >> And make do_overwritten() noinline so that it is really >> do_overwritten() which is called by lkdtm_WRITE_KERN(). >> >> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> >> --- >> drivers/misc/lkdtm/perms.c | 8 +++++--- >> 1 file changed, 5 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c >> index 60b3b2fe929d..442d60ed25ef 100644 >> --- a/drivers/misc/lkdtm/perms.c >> +++ b/drivers/misc/lkdtm/perms.c >> @@ -5,6 +5,7 @@ >> * even non-readable regions. >> */ >> #include "lkdtm.h" >> +#include <linux/kallsyms.h> > > Why not #include <asm/sections.h> instead here? dereference_symbol_descriptor() is defined in linux/kallsyms.h > >> #include <linux/slab.h> >> #include <linux/vmalloc.h> >> #include <linux/mman.h> >> @@ -37,7 +38,7 @@ static noinline void do_nothing(void) >> } >> >> /* Must immediately follow do_nothing for size calculuations to work out. */ >> -static void do_overwritten(void) >> +static noinline void do_overwritten(void) >> { >> pr_info("do_overwritten wasn't overwritten!\n"); >> return; >> @@ -113,8 +114,9 @@ void lkdtm_WRITE_KERN(void) >> size_t size; >> volatile unsigned char *ptr; >> >> - size = (unsigned long)do_overwritten - (unsigned long)do_nothing; >> - ptr = (unsigned char *)do_overwritten; >> + size = (unsigned long)dereference_symbol_descriptor(do_overwritten) - >> + (unsigned long)dereference_symbol_descriptor(do_nothing); >> + ptr = dereference_symbol_descriptor(do_overwritten); > > But otherwise, yup, I expect there will be a bunch of things like this > to clean up in LKDTM. :| Sorry about that! > > Acked-by: Kees Cook <keescook@chromium.org> > >> >> pr_info("attempting bad %zu byte write at %px\n", size, ptr); >> memcpy((void *)ptr, (unsigned char *)do_nothing, size); >> -- >> 2.31.1 >> >
diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c index 60b3b2fe929d..442d60ed25ef 100644 --- a/drivers/misc/lkdtm/perms.c +++ b/drivers/misc/lkdtm/perms.c @@ -5,6 +5,7 @@ * even non-readable regions. */ #include "lkdtm.h" +#include <linux/kallsyms.h> #include <linux/slab.h> #include <linux/vmalloc.h> #include <linux/mman.h> @@ -37,7 +38,7 @@ static noinline void do_nothing(void) } /* Must immediately follow do_nothing for size calculuations to work out. */ -static void do_overwritten(void) +static noinline void do_overwritten(void) { pr_info("do_overwritten wasn't overwritten!\n"); return; @@ -113,8 +114,9 @@ void lkdtm_WRITE_KERN(void) size_t size; volatile unsigned char *ptr; - size = (unsigned long)do_overwritten - (unsigned long)do_nothing; - ptr = (unsigned char *)do_overwritten; + size = (unsigned long)dereference_symbol_descriptor(do_overwritten) - + (unsigned long)dereference_symbol_descriptor(do_nothing); + ptr = dereference_symbol_descriptor(do_overwritten); pr_info("attempting bad %zu byte write at %px\n", size, ptr); memcpy((void *)ptr, (unsigned char *)do_nothing, size);
WRITE_KERN is supposed to overwrite some kernel text, namely do_overwritten() function. But at the time being it overwrites do_overwritten() function descriptor, not function text. Fix it by dereferencing the function descriptor to obtain function text pointer. And make do_overwritten() noinline so that it is really do_overwritten() which is called by lkdtm_WRITE_KERN(). Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> --- drivers/misc/lkdtm/perms.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)