Le 15/10/2021 à 23:31, Kees Cook a écrit :
On Thu, Oct 14, 2021 at 07:50:01AM +0200, Christophe Leroy wrote: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@xxxxxxxxxx> --- drivers/misc/lkdtm/perms.c | 25 +++++++++++++++++++++---- include/asm-generic/sections.h | 5 +++++ 2 files changed, 26 insertions(+), 4 deletions(-) diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c index 5266dc28df6e..96b3ebfcb8ed 100644 --- a/drivers/misc/lkdtm/perms.c +++ b/drivers/misc/lkdtm/perms.c @@ -44,19 +44,32 @@ static noinline void do_overwritten(void) return; }+static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)+{ + memcpy(fdesc, do_nothing, sizeof(*fdesc)); + fdesc->addr = (unsigned long)dst; + barrier(); + + return fdesc; +}How about collapsing the "have_function_descriptors()" check into setup_function_descriptor()? static void *setup_function_descriptor(func_desc_t *fdesc, void *dst) { if (__is_defined(HAVE_FUNCTION_DESCRIPTORS)) { memcpy(fdesc, do_nothing, sizeof(*fdesc)); fdesc->addr = (unsigned long)dst; barrier(); return fdesc; } else { return dst; } }
Ok
+ static noinline void execute_location(void *dst, bool write) { void (*func)(void) = dst; + 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); + if (have_function_descriptors()) + func = setup_function_descriptor(&fdesc, dst); func(); pr_err("FAIL: func returned\n"); } @@ -67,15 +80,19 @@ static void execute_user_location(void *dst)/* Intentionally crossing kernel/user memory boundary. */void (*func)(void) = dst; + 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); + if (have_function_descriptors()) + func = setup_function_descriptor(&fdesc, dst); func(); pr_err("FAIL: func returned\n"); }diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h index 76163883c6ff..d225318538bd 100644 --- a/include/asm-generic/sections.h +++ b/include/asm-generic/sections.h @@ -70,6 +70,11 @@ typedef struct { } func_desc_t; #endif+static inline bool have_function_descriptors(void)+{ + return __is_defined(HAVE_FUNCTION_DESCRIPTORS); +} + /* random extra sections (if any). Override * in asm/sections.h */ #ifndef arch_is_kernel_textThis hunk seems like it should live in a separate patch.
Ok I move it in a previous patch.
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