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| author |   Christophe Leroy <christophe.leroy@csgroup.eu> | 2022-02-15 13:41:06 +0100 |
|---|---|---|
| committer |   Michael Ellerman <mpe@ellerman.id.au> | 2022-02-16 23:25:12 +1100 |
| commit | b64913394f123e819bffabc79a0e48f98e78dc5d (patch) | |
| tree | 6bdf27b3d9814cf55f96d62d92731d04857aad60 /drivers/misc/lkdtm | |
| parent | lkdtm: Force do_nothing() out of line (diff) | |
| download | linux-dev-b64913394f123e819bffabc79a0e48f98e78dc5d.tar.xz linux-dev-b64913394f123e819bffabc79a0e48f98e78dc5d.zip | |
lkdtm: Really write into kernel text in WRITE_KERN
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. Export dereference_function_descriptor()
for when LKDTM is built as a module.
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>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/31e58eaffb5bc51c07d8d4891d1982100ade8cfc.1644928018.git.christophe.leroy@csgroup.eu
Diffstat (limited to 'drivers/misc/lkdtm')
| -rw-r--r-- | drivers/misc/lkdtm/perms.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c index 60b3b2fe929d..035fcca441f0 100644 --- a/drivers/misc/lkdtm/perms.c +++ b/drivers/misc/lkdtm/perms.c @@ -10,6 +10,7 @@ #include <linux/mman.h> #include <linux/uaccess.h> #include <asm/cacheflush.h> +#include <asm/sections.h> /* Whether or not to fill the target memory area with do_nothing(). */ #define CODE_WRITE true @@ -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_function_descriptor(do_overwritten) - + (unsigned long)dereference_function_descriptor(do_nothing); + ptr = dereference_function_descriptor(do_overwritten); pr_info("attempting bad %zu byte write at %px\n", size, ptr); memcpy((void *)ptr, (unsigned char *)do_nothing, size); |