[PATCH v2 12/13] lkdtm: Fix execute_[user]_location()
From: Christophe Leroy <hidden>
Date: 2021-10-14 06:25:17
Also in:
linux-arch, linux-mm, lkml
Subsystem:
char and misc drivers, generic include/asm header files, linux kernel dump test module (lkdtm), the rest · Maintainers:
Arnd Bergmann, Greg Kroah-Hartman, Kees Cook, Linus Torvalds
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 <redacted> --- 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; +} + 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_text
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2.31.1